synonymVideo memory(Video memory) generally refers to video card memory
Video memory, also calledFrame cache, which is used to storeGraphics card chipRender data processed or to be extracted.likecomputerThe video memory is used to store the data to be processedGraphic informationPart of.
Like computer memory, video memory is used to store data to be processedGraphic informationPart of.The picture we see on the screen is composed of pixelsDot compositionEach pixel uses 4 to 32 or even 64 bit data to control its brightness and color. These data must be saved in video memory and then submitted toDisplay chipAnd CPU, and finally convert the calculation result intoGraphic outputTo the display.Video memory, like motherboard memory, performs the function of storage, but it stores the information of each pixel output from the video card to the display.Video memory is a very important part of video card,Display chipAfter processing the data, it will be saved to video memory, and then RAMDAC(Digital to analog converter)Read data from video memory anddigital signalConvert toanalog signal, finally byScreen displayCome out.In advancedGraphics acceleratorVideo memory is not only used to storegraphic data , and was alsoDisplay chipIt is used for 3D function operation.Advanced in nVIDIADisplay chipAnd has developed andCPUParallel "GPUs"(Graphics Processing Unit)。“T&L”(deformation and lighting), etchigh-densityThe operation is completed by GPU on the video card, which makes the dependence on video memory more serious.Because of the role of video memory in the video card, it is obvious that the speed and bandwidth of video memory directly affect the overall speed of the video card.Video storage asmemoryIt has also experienced multipleDevelopment stageIt can even be said that the development of video memory is more active than motherboard memory, and has more varieties and types.Widely usedVideo memory typeyesSDRAMandSGRAM, better performanceDDR memoryFirst, it is applied to the graphics card, which improves the overall performance of the graphics card.DDR is guided by the success on the graphics card,Comprehensive developmentWhen it comes to motherboard systems, an era of DDR "three or two years ahead" will be presented to the world.
Mainly generated
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The graphics card is one on the motherboardBGA packageOfchipset, similar toCPU(Central Processing Unit), which is called GPU (Graphics Processing Unit) in the industry. There are nVIDIA andAMDTwo manufacturers.Graphics chipIt is equivalent to the CPU of the graphics card, but its main task is to process display informationprocess informationIt will generate a large amount of temporary data (unprocessed, being processed, and completed) during the process of. This requires a special place to store these temporary data, that is, video memory. It may also be a chip or just a part of the chip, depending on the hardware design (independent video card andintegrated graphics )。As for viewing the video memory size.It is generally displayed when you start up the computer. You can also click Properties Settings Advanced on the desktop--Adapter--Check "Memory Size" (XP system);Or right click on the desktop--Screen resolution--Advanced settings -- adapter. View the adapter information (Win7 system).
PCB: YesprintingCircuit board(Printed circuit board, PCB). It appears in almost every electronic device.If there are electronic parts in a certain device, they are all embedded on PCBs of different sizes.In addition to fixing various small parts, the main function of PCB is to provide mutual support between the upper partsElectrical connection。along withElectronic equipmentMore and more complicated, more and more parts are needed, and the lines and parts on the PCB are more and more dense.Bare plate (no parts on top) is also often called“Printed circuit boardPrinted Wiring Board(PWB)”。The base plate of the board itself is made of insulating and heat-insulating materials that are not easy to bend.The small line material visible on the surface isCopper foilThe original copper foil is covered on the whole board, but part of it isetchingAfter being disposed of, the remaining part will become a mesh of tiny lines.These lines are called conductor patterns or wiring, and are used to provide circuit connection of parts on PCB.Generally, the color of PCB is green or brown, which is the color of solder mask.It is insulatedProtective layerIt can protect copper wires and prevent parts from being welded to incorrect places.staySolder maskA layer of screen will be printed on thePrint side(silk screen)。Usually, words and symbols (mostly white) will be printed on it to mark the position of each part on the board.The screen printing surface is also called the icon surface.
working principle
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The working principle of the graphics card is that before the graphics card starts to work (graphics rendering modeling), the required materials and textures are usuallydata transferInto video memory.At the beginning of work (modeling and rendering), these data are generated byAGP busTransmission,Display chipThe data stored in the video memory will be extracted through the AGP bus. In addition to the modeling and rendering data, there are a lot of vertex data and workInstruction flowThe data needs to be exchanged. These data are converted toanalog signalThe output to the display end is the image we see.Display chipWith the increasing performance, its data processing ability is becoming stronger and stronger, which makes the video memorydata transmissionQuantity andTransmission rateIt also has higher requirements, and the video card has higher requirements for video memory.CarrierExchange volumeThe size and speed ofVideo card coreThe efficiency of video memory is very important, and how to effectively improve the efficiency of video memory is to improve the overall efficiency of video memoryDisplay cardThe key to effectiveness.
Distinguishing types
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overview
AsDisplay cardAs an important part ofDisplay chipAnd gradually changed.From early EDORAMMDRAM、SDRAM、SGRAM、VRAMThe DDR SDRAM video memory widely used by WRAM has experienced many generations of progress.Used in the marketVideo memory typeThere are mainly three kinds of SDRAM, DDR SDRAM and DDR SGRAM.SDRAM particles are mainly used inLow end video cardIn general, the frequency does not exceed 200MHz. It has no advantages over DDR in price and performance, so it is gradually replaced by DDR.DDR SDRAM is the mainstream in the market (including DDR2 and DDR3). On the one hand, the process is mature, and mass production leads to lower costs, making it cheap;On the other hand, it can provide high operating frequency and bring excellent data processing performance.As for DDR SGRAM, it is designed for graphics card manufacturers to meet the needs of plotters. In order to enhance the efficiency of graphics access processing and drawing controlDynamic random access memory(SDRAM).SGRAM allows you to modify or access data in memory individually in blocksa central processor(CPU) synchronization can reduce the number of memory reads and increase the efficiency of the drawing controller. Although it has good stability and good performance, its overclocking performance is poor and is rarely used at present.
FPM DRAM
FPMDRAM(Fast Page Mode RAM): fast page mode memory.It is a kind of memory (also used as video memory) that was widely used in the 486 period.72 lines, 5V voltage, 32bit bandwidth, basic speed of more than 60ns.Its reading cycle starts from the triggering of a line in the DRAM array, and then moves toMemory addressThe indicated location contains the required data.The first piece of information must be verified to be valid and stored in the system before it can be ready for the next cycle.This introduces the "waiting state", because the CPU must wait foolishly for the memory to complete a cycle.One important reason why FPM is widely used is that it is a standard and safe product, and it is very cheap.But its performance defects led it to beEDO DRAMInstead, the video card of this kind of video memory no longer exists.
EDO
EDO(Extended Data Out) DRAM. Compared with FPM, EDO DRAM is 5% faster. This is because EDO has alogical circuitBy this way, EDO can read the next data into memory before the end of the last memory data reading.Designed assystem memoryEDO DRAM is very expensive originally, just because the PC market needs an alternativeFPM DRAMTherefore, it is widely used on the fifth generation PC.EDO video memoryIt can work at 75MHz or higher, but its standard working frequency is 66MHz, but its speed still cannot meet the needs of display chips, and it has become a video memory only available on "antique" products.
SGRAM
SGRAMSYNCHRONOUS GRAPHICS DRAM is an abbreviation for Synchronous Graphics RAM, which means that synchronous graphics RAM is a kind of video memory specially designed for video cards and has strong graphics read-write abilitySDRAMImproved.It improves the low transmission rate of inefficient video memory in the pastDisplay cardThe improvement of performance creates conditions.When SGRAM reads and writes data, it does not read one by one, but takes "Block" as the unit, thus reducing the times of overall memory reading and writing, and improving the efficiency of the graphics controller.But its designManufacturing costIt is higher, and is more used in high-end graphics cards at that time.At present, this kind of video memory has been basically not used by manufacturers, but replaced by DDR video memory.SDRAM,Synchronous DRAM (synchronous dynamic random access memory) was once the most widely used type of PCMemory typeEven today, SDRAM still has a place in the market.Since it is "synchronous dynamic random access memory", it means that its working speed is the same as that of the systemBus speedSynchronized.SDRAM memoryIt is divided into PC66, PC100, PC133 and other specifications, and the number after the specification represents the maximum normal operation of the memorysystem bus Speed, such as PC100, means that this memory can work synchronously in the computer with 100MHz system bus.Andsystem bus Speed synchronization, that is, with the systemClock synchronization, which avoids unnecessary waiting cycles and reducesdata storage Time.Synchronization also makesStorage controllerKnow which oneClock pulseThe period is used by the data request, so the data can start to transmit during the pulse rise period.SDRAM uses 3.3Vworking voltage , 168PinDIMMInterface with 64 bit bandwidth.SDRAM is not only used in memory, but also in video memory.SDRAM can work synchronously with CPU, without waiting cycle and reducing dataTransmission delay。Advantages: Low price, it has been widely used in low-end video cards.SDRAM has lost its popularity since DDR SDRAM became mainstream. At present, SDRAM can only be used in the lowest end products orFlea marketOnly then can we see such video storage products.
DDRThere are two kinds of video memory. One is DDR memory, which we are used to. Strictly speaking, DDR should be called DDR SDRAM.The other is DDR SGRAM, which is rarely used.
DDR SDRAM
DDR SDRAMPeople are used to calling DDR SDRAM DDR.DDR SDRAM is the abbreviation of Double Data Rate SDRAM, which means double rate synchronous dynamic random access memory.DDR SDRAMIt is developed on the basis of SDRAM and still uses the SDRAM production system. Therefore, for memory manufacturers, it is only necessary to slightly improve the equipment that makes ordinary SDRAM to realize the production of DDR memory, which can effectivelycost reduction。RAM transmits data only once in a clock cycle. It transmits data during the rising period of the clock;DDR memory transmits data twice in a clock cycle. It can transmit data once in the rising and falling periods of the clock, so it is called double rate synchronous dynamic randomstorage。DDR memory can be stored in the sameBus frequencyRelease higher dataTransmission rate。Compared with SDRAM: DDR uses a more advanced synchronization circuit, so that the main steps of the designated address, data transmission and output are executed independently, while maintaining full synchronization with the CPU;DDR uses DLL (Delay Locked Loop, which provides aData filteringSignal) technology, when the data is valid, the storage controller can use this data filtering signal to accurately locate the data, output it every 16 times, and resynchronize the data from different memory modules.DDL does not need to be improved in essenceclock frequencyCan double the speed of SDRAM, which allowsClock pulseOfRising edgeandFalling edgeRead data, so its speed is twice that of standard SDRA.DDR SDRAM is the most widely usedVideo memory typeMore than 90% of video cards use this type of memory.
DDR SGRAM
DDR SGRAMIt is developed from SGRAM. It also transmits data twice in a clock cycle. It can transmit data once in the rising period and once in the falling period of the clock.It can be changed without increasing the frequencyData transmission rateDouble.DDR SGRAM is better than DDR SDRAM in performance, but its cost is still higher than DDR SDRAM, and it is only used in a few products.And itsOverfrequencyThe capability is weak, and it is easy to be damaged due to overclocking due to its structural problems.DDR2 video memoryIt can be regarded as an upgrade and expansion of DDR video memory. DDR2 video memory takes the "2 bit" of DDR video memoryPrefetch(2-bit prefetch) technology is upgraded to the "4-bit prefetch" mechanismCore frequencyLower its validityFrequency ratioDDR video memory has been doubledBit widthIn the case ofVideo memory bandwidthIt has also doubled, which is very beneficial to the performance improvement of the graphics card.Technically, the DRAM core of DDR2 video memory can be accessed in parallel. It processes 4 data in each access instead of 2 data in DDR video memoryDDR2The video memory can process 4bit data in each clock cycle, which is twice as much as the 2bit data processed by traditional DDR video memory.Compared with DDR video memory, another improvement of DDR2 video memory is that it uses 144Pin sphericalPinOfFBGAPackaging methodReplace the traditionalTSOPThe working voltage is also reduced from 2.5V to 1.8V.As DDR2 video memory provides higher frequency, the performance is improved correspondingly, but it also bringsCalorific valueThe disadvantages of.Combined with structural constraints, it is impossible to adopt cheapTSOP packageThe BGA packaging with higher cost has to be adopted (the initial capacity of DDR2 is insufficient, and the cost problem is even worse).High calorific value and high price have become common problems in using DDR2 video memory cards. For example, GeForce FX 5800/5800Ultra series video cards that first used DDR2 video memory are relatively failed products.For the above reasons, DDR2 is not widely used in mainstream video cards.
DDR3
DDR3Video memory can be regarded as an improved version of DDR2. They have many similarities, mainly using 144Pin spherical pin FBGA packaging.However, the DDR3 core has been improved: the DDR3 video memory uses 0.11 μ mProduction processThe power consumption is significantly lower than that of DDR2.In addition, DDR3 video memory uses "Pseudo Open Drain"Interface technology, as long as the voltage is appropriate,Display chipDDR3 video memory can be directly supported.of course,PhanerophoreLongerdelay time (CAS latency) has always been a common problem of high frequency video memory, and DDR3 is no exception. The CAS latency of DDR3 is 5/6/7/8, compared with 3/4/5 of DDR2.Objectively speaking, compared with DDR2, DDR3 has not made rapid progress in technology, but its performance advantages are still obvious: (1) power consumption andCalorific valueSmaller: learned lessons from DDR2Control costsOn the basis of, it reduces energy consumption and heat generation, making DDR3 easier to be accepted by users and manufacturers.(2) Higher operating frequency: Due to lower energy consumption, DDR3 can achieve a higher operating frequency, which to some extent makes up for the disadvantage of longer delay time. At the same time, it can also be one of the selling points of the video card, which has been shown in the video card with DDR3 video memory.(3) Reduce the overall cost of graphics card: DDR2PhanerophoreThe specifications are mostly 4M X 32bit, and the 128MB video memory commonly used with high-end video cards requires 8.The DDR3 video memory is mostly 8M X 32bit, and the single particle size is large. Four of them can form 128MB video memory.In this way, the PCB area of the graphics card can be reduced, and the cost can beEffective controlIn addition, when the number of particles is reduced, the video memory power consumption can be further reduced.(4) Good versatility: Compared with DDR changing to DDR2, DDR3 hascompatibilityBetter.becausePin, packaging and other key features remain unchanged, and the DDR2Show CoreandPublic editionThe designed graphics card can use DDR3 video memory with a little modification, which is beneficial to manufacturers to reduce costs.At present, DDR3 appears to existNewMost of the high-end graphics cards have been widely used.
GDDR5
Video storage picture
GDDR5(Graphics Double Data Rate, version 5) SDRAM isapplication programA type of high-performance DRAM video memory designed for high frequency bandwidth requirements.Like the previous version(GDDR4)GDDR5DDR2SDRAMWith double speedDDR3 SDRAMHowever, GDDR5 also has an 8-bit wide prefetch cache similar to GDDR4.
Now?SamsungandQimondaGDDR5 has startedDevelopment plan。Samsung ElectronicsFrom the third quarter, 5000/3200 Mibps GDDR5 video memory will be taken out. This video memory adopts 170FBGA packaging, GDDR5x32 512Mbit G-Die process, and the working voltage is 1.5v.From the end of this year to the beginning of next year, 1Gb GDDR5 video memory with GDDR5x32170FBGA specification, D-Die process and 1.5v working voltage will be produced.Qimonda is also expected to pilot produce GDDR5 video storage at the end of this year, and put it into mass production in the first quarter of next year.
Today, GDDR3 is the type of video memory commonly equipped on video cards, and GDDR4 is only a few high-end models. Qimonda, which is determined to develop by leaps and bounds, has trial produced the world's first GDDR5.
Performance capacity
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Video memory
Memory capacityIt's a video cardUpper LocalThe capacity of video memory, which is one of the key parameters for selecting video card.The size of video memory capacity determines the temporary video memoryStore dataTo some extent, it will also affect the performance of the graphics card.With the development of video card, the video memory capacity is gradually increasing, and there is a growing trend.The video memory capacity has grown from 512KB, 1MB, 2MB and other small capacities in the early days to 64MB, 128MB, 256MB, 512MB, 768MB, until the current mainstream 2GB, 4GB, 6GB and high-end video cards 8GB, 16GB, 32GB. Some professional video cards even have 48GB video memory.stayMaximum resolution of graphics cardOn the other hand, the maximum resolution is directly related to the video memory to some extent, because the data of these pixels are initially stored in the video memory, so the video memory capacity will affect the maximum resolution.When the video memory capacity of the early video card was only 512KB, 1MB, 2MB and so on, the video memory capacity was really a bottleneck of the maximum resolution;But at present, the video memory capacity of mainstream video cards, even 64MB, has been eliminated. The mainstream entertainment video cards have reached 512MB or 1GB, and some professional video cards even have 4GB of video memory. In this case, the video memory capacity is no longer a factor affecting the maximum resolution.In terms of graphics card performanceDisplay chipThe processing capacity of the3D GamesAnd professional rendering requires more and more data to be temporarily stored, and the required video memory capacity is also increasing. To some extent, the video memory capacity will also affect the performance of the video card.For example, when the display core is strong enough and the video memory capacity is small, there is a large amount of texture mapping data to be stored. If the video memory capacity is not enough to store these data, the display core will only be idle for some time to wait for the completion of these data processing, which affects the performance of the display core and thus the performance of the video card.It is worth noting that the larger the video memory capacity is, the higher the performance of the video card is not necessarily, because the three factors that determine the performance of the video card are the first one usedDisplay chip, followed by video memory bandwidth (which depends on the video memory bit width andMemory frequency), and finally the video memory capacity.The proper video memory capacity of a video card is determined by its useDisplay chipThat is to say, it is reasonable that the video memory capacity should match the performance of the display core. The higher the performance of the display chip, the higher the processing capacity, the larger the video memory capacity should be. However, the low performance display chip with large capacity video memory does not help its performance.For example, some commercially available video storage devices with 512MB large capacityRadeonIn terms of graphics card performance, the 9550 graphics card is better than the Radeon 9550 graphics card with 128MB video memoryCore frequencyandMemory frequencyThe parameters are the same, because the relatively low processing capacity of the Radeon 9550 display core determines that it is meaningless to equip it with a large capacity video memory. On the contrary, the large capacity video memory also brings about the problem of increased purchase costs.
data
Data bit refers to the number of bits that can be transmitted within a clock cycle. It is an important factor that determines the video memory bandwidth and is closely related to the performance of the video card.When video storageSame kindAnd when the operating frequency is the same, the larger the number of data bits, the higher its performance.The calculation method of video memory bandwidth is:Operating frequency× Data bandwidth/8.Taking the current GeForce3 video card as an example, its video memory system bandwidth=230MHz × 2 (multiplied by 2 because DDR video memory is used) × 128/8=7.36GB.
Data bit is a very important parameter of video memory and video card.On the graphics cardworking processMedium, ZBuffer、Frame bufferAnd texture buffers will consume video memory bandwidth resources significantly.Bandwidth is3D chipCompared with the data volume standard transmitted by the local memory, the video memory capacity is not important at this time, nor will it affect the bandwidth. There is little difference in performance between 64MB and 32MB video cards with the same video memory bandwidth.Because the bottleneck of the system is the video memory bandwidthPixel Shader When working, insufficient video memory bandwidth will cause data transmission congestion, resulting inDisplay chipWaiting affects speed.Video memory is mainly divided into 64 bit and 128 bit. Under the same operating frequency, the bandwidth of 64 bit video memory is only half of that of 128 bit video memory.This is why the performance of Geforce2 MX200 (64 bit SDR) is far inferior to that of Geforce2 MX400 (128 bit SDR).
Memory interface
Video memory
The bit width of video memory is the number of bits of data that can be transmitted by video memory within a clock cycle. The larger the number of bits, the larger the amount of data that can be transmitted instantly. This is one of the important parameters of video memory.At present, there are three kinds of video memory bit widths in the market: 64 bit, 128 bit and 256 bit. The 64 bit video card, 128 bit video card and 256 bit video card are the corresponding video memory bit widths.The higher the bit width of video memory, the better the performance and the higher the price. Therefore, 256 bit wide video memory is more used in high-end video cards, while 128 bit video memory is basically used in mainstream video cards.As you know, video memory bandwidth=Memory frequencyX video memory bit width/8, the video memory bit width will determine the video memory bandwidth when the video memory frequency is the same.For example, the sameMemory frequencyIt is 500MHz 128 bit and 256 bit video memory, so the video memory bandwidth of the two will be respectively: 128 bit=500MHz * 128 / 8=8GB/s, and 256 bit=500MHz * 256 / 8=16GB/s, which is twice the 128 bit. It can be seen that the importance of video memory bit width in video memory data.The video memory of the video card is composed of video memory chipsBit widthAlso byPhanerophoreThe bit width of,.Video memory bit width=PhanerophoreBit width × number of display particles.PhanerophoreThere are memory numbers of relevant manufacturers on the Internet. You can find their numbers on the Internet to find outBit width, and then multiply by the number of video memory particles to get the bit width of the video card.This is the most accurate method, but it is troublesome to implement. Here's a simple one, but it is only suitable for general conditions. There are some special cases, and it can be applied in most cases.At present, there are mainly two packaging forms of video memory: TSOP and BGA. Generally, the video memory packaged with BGA is 32 bits/chip, while the video memory packaged with TSOP is 16 bits/chip/.If the graphics card uses four BGA packaged video memories, itsBit widthIt is 128 bit. If eight TSOP packaging particles are used, the bit width is 128 bit. However, if only four TSOP packaging particles are used in the graphics card, the video memory bit width is only 64 bit.This is just a general technique, not necessarily suitable for all situations. To make the most accurate judgment, you'd better check the video memory number!
bandwidth
Video memory bandwidth isDisplay chipThe larger the bandwidth, the faster the communication between the display chip and the video memory.To indicate this width, the unit of video memory bandwidth is: bytes/second.The bandwidth of video memory and itsBit widthAnd the speed of video memory (that is, the working frequency).The final conclusion: video memory bandwidth=video memory bit width ×Memory frequency/8。The speed of video memory is generally in ns, and the common video memory is 6ns, 5.5ns, 5ns, 4ns, 3.8ns, up to 1.8ns.The corresponding operating frequencies are 143MHz, 166MHz, 183MHz, 200MHz, 250MHz and up to 550MHz.The calculation method of operating frequency is very simple -Video memory speedThe reciprocal of is the rated operating frequency of video memory, such asClock cycleIf it is 4ns, the operating frequency of this video memory is 1/4ns=250MHz (if it is DDR video memory, multiply the result by 2).
For example, if the display resolution is 1024x768 and the number of color bits is 32bit, the required video memory capacity=1024x768x32bit/8bit=3145728byte, but this is for 2D graphics card (ordinary plane), if it is3D accelerator card, the required video memory capacity is 1024x768x32bitx3/8bit=9437184byte=9.216MB, which is the minimum requirement, and a certain amount of capacity must be added as texturedisplay memory, otherwise, when the display resource is fully occupied, the computer will onlyMain memoryAs texture memory, such a second call will result inDisplay performanceAs a real 3D accelerator, its video memory capacity must be greater than 9.216MB.The video memory of workstation video card is more than 64MB.For example, 2D drawing applications, even in the case of 1600x1200, can be up to 1600x1200x32bit/8bit=7680000byte=7.5MB. For 3D drawing applications, such as3D Studio Max, then the capacity requirement is 7.5x3=22.5MB, but this is the minimum requirement, so 32MB video memory is used to cope with this kind of2DVideo playback of drawing or entertainment, general3D design。For workstations, since they run larger software and larger operations, the video memory is more than 256M.
Basic knowledge
The speed of video memory is generally in ns.Common video memories include 7ns, 6ns, 5.5ns, 5ns, 4ns and even 3.8ns.The corresponding rated operating frequencies are 143MHz, 166MHz, 183MHz, 200MHz and 250MHz.Rated operating frequency=1/video memory speed.Of course, for some high-quality video memories, there is a certain margin for the actual maximum operating frequency of video memories.The overclocking of video memory is based on this principle, as shown inRated frequency6ns video memory exceeds the operating frequency of 190MHz.Here we will also talk about the actual operating frequency and the equivalent operating frequency of video memory.DDR video memory can transmit data on both the rising and falling edges of the clockclock frequencyandData bitsIn the case of width, the video memory bandwidth is twice that of ordinary SDRAM.In other words, the actual working frequency of DDR video memory is normal when the video memory speed is the sameSDRAM video memory2 times.Similarly, the bandwidth of DDR video memory is twice that of ordinary SDRAM video memory.For example, the working frequency of 5ns SDRAM video memory is 200MHZ, while the equivalent working frequency of 5ns DDR video memory is 400MHZ. But it should be understood that when the video card is manufactured, the manufacturer has set the actual working frequency of the video memory, and the actual working frequency is not necessarily equal to the maximum frequency of the video memory.This kind of situation is more common now. For example, the video memory can work at 650 MHz at most, but the operating frequency of the video card is set to 550 MHz during manufacturing, and there is a certain overclocking space in the video memory.This is also the method commonly used by manufacturers at present. The selling point of video card is overclocking.
list
The video memory used for the video card is also called the memory used for the motherboardDDR、DDR2、DDR3、DDR4However, due to the large difference in specification parameters, they cannot be used universally. Therefore, video memory types are also divided into GDDR, GDDR2, GDDR3, GDDR4 and mainstream GDDR5.
Frequency corresponding to video memory speed corresponds to DDR frequency
6NS 166MHZ 333MHZ
5NS 200MHZ 400MHZ
4NS 250MHZ 500MHZ
3.6NS 278MHZ 556MHZ
3.3NS 300MHZ 600MHZ
2.8NS 360MHZ 720MHZ
2.2NS 450MHZ 900MHZ
2NS 500MHZ 1000MHZ
Memory frequency
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Memory frequencyIt refers to the frequency when the display is stored on the video card by defaultMHz(megahertz).Memory frequencyTo some extent, it reflects the speed of the video memory.Memory frequencyIt varies with the type and performance of video memory,SDRAM video memoryThey usually work at a lower frequency, usually 133MHz and 166MHz,Memory frequency, mainly inMedium and low end graphics cardUsed on,DDR2 video memoryDue to high cost and average performance, the usage is not large.DDR3 video memoryIt is the most widely used high-end graphics cardVideo memory type。Different video memories can provideMemory frequencyThere are also great differences, mainly including 400MHz, 500MHz, 600MHz, 650MHz, and 800MHz, 1200MHz, 1600MHz, and even higher in high-end products.
Video memory frequency vsVideo memory clock cycleIs related, and they are in reciprocal relationship, that is, video memory frequency=1/video memoryClock cycle。If it isSDRAMIf the clock cycle of video memory is 6ns, itsMemory frequency1/6ns=166 MHz.ForDDR SDRAMperhapsDDR2、DDR3, its clock cycle is 6ns, then itsMemory frequency1/6ns=166 MHz, but it is important to know that this is the DDR SDRAMActual frequencyInstead of what we usually sayDDR video memoryFrequency.Because DDR transmits data in both the rising and falling periods of the clock, it transmits data twice a cycle, which is twice the SDRAM frequency.The habitually called DDR frequency is its equivalent frequencyworking frequency Multiply by 2 to get the equivalent frequency.Therefore, 6ns DDR video memoryMemory frequency1/6ns * 2=333MHz.For details, see the introduction of various video memories below.However, it should be understood that when the video card is manufactured, the manufacturer has set the actual working frequency of the video memory, and the actual working frequency is not necessarily equal to the maximum frequency of the video memory.This kind of situation is common. For example, the video memory can work at 650 MHz at the maximum, but the operating frequency of the video card is set to 550 MHz at the time of manufacturingOverfrequencySpace.This is the usual method used by manufacturers. The video card sells on overclocking.GDDR3。
Video memory package
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Video memory packageMeansPhanerophoreAdoptedPackaging technologyType, packaging is to wrap the video memory chip to avoid contact with the outside world and prevent damage to the chip from the outside world.Impurities and undesirable gases in the air, evensteamWill corrode the precision circuit on the chip, and then cause the electrical performance to decline.Different packaging technologies differ greatly in manufacturing processes and processesMemory chipThe exertion of its own performance also plays a vital role.Video memoryPackaging formMainlyQFP、TSOP-II、MBGATSOP-II and MBGA are common.TSOP-II was widely used in early SDRAM and DDR video memory, but now withVideo memory speedAs a result, more and more video memories use MBGA packaging, especially DDR2 and DDR3 video memories, which all use MBGA packaging.In addition, many manufacturers also refer to the packaging of DDR2 and DDR3 video memory asFBGA, this kind of address is more focused onPinThe naming of the arrangement is actually the same packaging form.In addition, compared with TSOP-II, MBGA can achieve higherMemory frequencyHowever, it is not easy to think that the video memory packaged with MBGA must be better than the video memory, because whether it is easy to overclock depends more on the difference between the default frequency agreed by the factory and the actual frequency that the video memory can reach, including the design and manufacture of the video card. Simply speaking, the video memory packaged with MBGA can reach a higher frequency, but its default frequency is also higher.
QFP
QFPIt is the abbreviation of Package, which means "small square plane package".QFP packageIt is frequently used on early video cards, but few QFP packaged video memory with a speed of more than 4ns. Because of the problems of process and performance, it has been gradually used by TSOP-II andBGAReplaced by.The QFP package has pins around the particles, which can be clearly identified.TSOP-II (Thin Small Out Line Package).TSOP packageMake pins around the chip, and useSMTTechnology(Surface mounting technology)Directly attached toPCB boardSurface.TSOP packageOverall dimensionParasitic parameters (when the current changes significantly, the outputVoltage disturbance)It is small, suitable for high-frequency applications, easy to operate, and high reliability.At the same time, TSOP package hasYieldIt is high and cheap, so it is widely used.TSOP packaging is the most widely usedVideo memory packageType.TSOP-II package pins are on both sides of the video memory.
MBGA
MBGARefers to microBall grid array package, the full English name is Micro Ball Grid Array Package.It is connected with TSOPMemory chipDifferent from that, the pins of MBGA are not exposed, but parasitic at the bottom of the chip in the form of tiny solder balls, so the pins cannot be seen in this video memory.The advantages of MBGA areNoiseLess, good heat dissipationElectrical performanceGood, can connect more feet, and can improveYield。The most prominent reason is that the internal components have smaller spacingTransmission delaySmall, which can greatly improve the frequency.The most prominent feature is the smaller spacing of internal componentsTransmission delayShort, which can greatly improve the frequency.Compared with TSOP packaged video memory, MBGA video memory has excellent performance.But it also puts forward requirements for circuit wiring. The former only needs 66Pin, and the lead is very long, and they are all lying on the PCB board, so it is relatively easy to design, weld, process and detect;The area of the latter is only about 1/4 of that of the former, but it has 144Pin. Each Pin is tinyTin ballIt is much more difficult to design and produce.In the early days, many SDRAM and DDR video memories used TSOP-II. Now, with the improvement of video memory speed, more and more video memories use MBGA packaging, especially DDR2 and DDR3 video memories, which all use MBGA packaging.In addition, many manufacturers also use DDR2 and DDR3Video memory packageIt is called FBGA, which is more focused on the naming of the pin arrangement. It is actually the same packaging form.
Clock cycle
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Video memoryClock cycleIs video storageClock pulseAs a measure ofVideo memory speedImportant indicators.The faster the video memory speed is, the greater the amount of data exchanged per unit time is. In the same case, the performance of the video card will be significantly improved.The clock cycle of video memory is generally in ns(nanosecond)Is the unit, and the operating frequency is inMHzIs the unit.Video memory clock cycleFollowworking frequency One-to-one correspondence, the relationship between them is: working frequency=1 ÷ clock cycle × 1000.thatMemory frequencyIf it is 166MHz, its clock cycle is 1 ÷ 166 × 1000=6ns.aboutDDR SDRAMperhapsDDR2、DDR3 video memoryFor example, the equivalent is used to describe its operating frequencyoutput frequency 。Because it canRising edgeandFalling edgeCan transmit data, so when the operating frequency andData bitsWith the same width,Video memory bandwidthyesSDRAMTwice as much.In other words, the equivalent output frequency of DDR SDRAM video memory is twice that of SDRAM video memory when the video memory clock cycle is the same.For example, the working frequency of 5ns SDRAM video memory is 200MHz, while the equivalent working frequency of 5ns DDR SDRAM or DDR2 and DDR3 video memory is 400MHz.Common video memory clock cycles are 5ns, 4ns, 3.8ns, 3.6ns, 3.3ns, 2.8ns, 2.0ns, 1.6ns, 1.1ns, or even lower.