Memory picks the motherboard? I don't know, who can explain?

A computer must have an arithmetic unit, a controller, a memory and input and output devices. The functions of arithmetic unit and controller are completed by CPU, and the memory is divided into internal memory and external memory. Internal memory is mainly memory, and external memory includes hard disk, CD-ROM drive, tape drive and many other products. This week, I will talk about some views on memory purchase, hoping to help you make the right choice when saving your computer.

First, why do you need more memory?

I believe many people familiar with computers have heard the saying: If you have a little money for upgrading, investing in increasing memory can get more performance improvement than investing in upgrading CPU. This is a very reasonable statement. The faster the CPU, the better, but the speed increase between PII300 and PII350 may be imperceptible to the naked eye. If you buy a piece of 128M memory with a price difference of more than 700 yuan, you will obviously speed up running the operating system, application software and playing games. Therefore, memory can be said to be the component that has the greatest influence on computer performance except CPU. Sometimes, its status has even surpassed that of CPU.

At present, many consumers who don't know much about computers or know nothing about computers often fall into a misunderstanding when purchasing computers, that is, the faster the CPU, the better. They only look at the speed of CPU and don't care about other aspects of configuration. Therefore, in view of the mentality of these consumers, some merchants have launched a lot of slogans such as "Buy PIII450 complete machine in 7999" and "Buy PII400 complete machine in 5555", which at first glance seems to be very cost-effective. However, as long as you pay attention to the configuration of these models, most of them are 32M memory and 14 inch color display. Some of them use 4M or 8M AGP graphics cards (in fact, SIS6326 and I740 cost two or three hundred yuan), and some even use 2M S3 375 to reduce costs. The performance of these so-called PIII450 and PII400 may not be as good as 64M memory +K6-2/300, not to mention 128M memory+Celeron 366. This is because of the bottleneck phenomenon.

The easiest bottleneck of CPU speed is memory. Because when applications run, they are first stored in memory. In order to perform a task, the processor must access the memory and get instructions from it. Reducing the time of accessing memory is helpful to improve the performance of the whole machine. There are two ways to reduce the memory access time: one is to use a memory cache, usually called L2 cache. The memory cache can be regarded as the processor's ultra-high speed memory. It is several times faster than standard memory. The cache controller moves frequently used data from slow memory to cache. Then, the processor gets the required data from the cache so that it can work in time. However, the price of cache is very high, and it is impossible to increase the number of caches indefinitely, because when the number of caches increases to a certain number, it will inevitably increase the addressing ability of CPU and reduce the performance of the system. Another method is to use main memory. The amount of main memory in the system will greatly affect the performance, especially when using multi-user operating systems such as WINDOWS95/98/NT and some applications. Because the larger the memory capacity in the system, the more data can be stored in the storage unit closer to the CPU, instead of being stored in other storage media such as slow hard disks. For multiple applications running at the same time, this phenomenon is more prominent, because these applications all need to use a certain amount of main memory space, otherwise they can only use the hard disk for virtual memory, which will inevitably make the CPU access the hard disk more and lead to the decline of system performance. Of course, after the amount of memory increases to a certain extent, the marginal utility obtained by increasing a certain amount of memory will continue to decrease, and the performance of the system will not be improved until more memory is added.

Second, how much memory is needed?

The demand for memory mainly depends on the operating system and software used. For WINDOWS95/97, you need 16M memory, preferably 32M memory, otherwise the system will react slowly when running multiple applications at the same time. WINDOWS98 must have at least 32M memory, otherwise it will be very slow, and 64M can make it run well. If you often use software such as OFFICE97, I suggest you add 16M to the recommended memory. If you often play 3D games, you'd better multiply the recommended memory by 2 to suit your capacity. As for PHOTOSHOP, AUTO CAD, 3DS MAX and other large-scale software or a LAN server, the more memory, the better. Networms who often surf the Internet also need a lot of memory capacity, because every time they open a browser window or IRC, they need memory to download software. The more windows you have, the more you can save on the Internet, provided, of course, that the bandwidth of the Internet is large enough. Networms can have as much memory configuration as game enthusiasts. Using NT needs to use twice as much as WINWOWS95/97/98 at the same time, because NT takes up a lot of memory as soon as it is turned on, especially NT server.

If you are an ordinary user, you can't predict which software you will use frequently in the future when you purchase the machine. You can determine the amount of memory you need according to the following methods. This method is general, but it is absolutely simple and practical for ordinary users, that is, determine the memory capacity according to your CPU speed. At present, the slowest CPU on the market may be MII233 of CYRIX and MMX200 of INTEL. Cpus of this level and below are equipped with at least 32M memory. Even with 486 DX/80, after the memory is upgraded from 16M to 32M, you can play games like Age of Empires smoothly. Therefore, for the CPU with the main frequency below 233MHz, the recommended capacity is 32M. In the CPU with the main frequency of 233MHz to 300MHz, I hope you can be equipped with 64M memory, because most computers with this level of CPU are equipped with WINDOWS 98, and 64M memory can meet the needs of your operating system, common application software and most 3D games. 96M memory is a good choice for CPU with frequency of 300MHz to 400MHz. In fact, the general demand of 64M is enough. Considering that most users who use this level of CPU will be interested in the most popular 3D games, otherwise there is no need to buy such a good CPU, so it is recommended to use 96M memory. This capacity of memory can complete all 3D games well. Finally, there are CPUs above 400MHz. This part of CPU includes two kinds, one is high-grade CPU such as PIII450/500, and the other is overclocked by low-frequency CPU such as Celeron 300A. In short, most people who use this level of CPU are experienced DIY enthusiasts, overclocking enthusiasts and some rich and fashionable people. Undoubtedly, 128M memory is the least choice. For DIY enthusiasts and overclocking enthusiasts, they are likely to have high-end AGP graphics cards with 16M or even 32M memory, not to mention these in order to get better game pictures and test results. And those users who have the money to buy PIII450 will still feel heartbroken about buying a 128M memory for 7XX?

Using the above selection method, although it can't be said to be the best choice for your computer, there will never be the joke of PIII450 with 32M memory mentioned above (for PIII, 64M is actually too little), nor will it cause the bottleneck of your computer, let alone bind your high-speed CPU with poor memory. If you don't want to play some demanding simulator games (such as N64) or do graphics, the memory performance above 128M is not much different from that of 128.

Third, the old computer expanded its memory.

With the continuous decline of memory price, the recent price is less than half of that of the New Year. Many users naturally intend to take this opportunity to expand their memory and prepare for the arrival of WINDOES2000. Here are some precautions for expanding the memory of old computers.

1) For users who are still using SIMM memory, SIMM memories with different capacities cannot be mixed in the same Bank. In other words, the memory capacity in each bank group should be consistent, such as 4M*2, 8M*2, 16M*2. It is best not to use a 4M and an 8M like this.

2) Don't mix SIMM memories with different speeds, even if the capacity is the same. Memory mixed insertion with different speeds will also cause system instability.

3) Know the maximum memory limit supported by your computer and the maximum capacity of each memory, which can be seen from the instruction manual of the motherboard. If your motherboard only supports 64M memory per memory module, then you can't use 128M memory on your motherboard.

4) Users who use DIMM (SDRAM) had better use the same brand or even the same memory chip number when expanding, which can avoid many possible compatibility problems.

Four. Matters needing attention in purchasing PC 100 memory

Since SIMM is no longer in the mainstream market, the current memory is DIMM memory, which is SDRAM. At present, the CPU of newly purchased users mostly uses the external frequency of 100MHz, and many overclocking enthusiasts also work at the external frequency of 100MHz, which exceeds the PII350 of the original external frequency of 100MHz to12 MHz and 124MHz. To work at external frequencies of 100MHz and higher, the memory must conform to the PC 100 specification.

The so-called PC 100 memory refers to the SDRAM that can work synchronously and stably with the motherboard external frequency (100MHZ) when the motherboard external frequency is 100MHZ and CAS is set to 2. Some SDRAM can work stably when CAS is set to 3, which can barely be considered as PC 100 memory.

Let's take a look at the main reasons that affect the quality of SDRAM:

1) Memory particle mass. Companies that produce storage particles include LGS, NEC, Hitachi, Samsung, Toshiba, Jinma and Micron. To make the memory meet the PC 100 specification, the memory particles of these companies must first pass the PC- 100 test, that is, when CL=3, tCK should not be slower than 10ns, and tAC should not be slower than 6ns ((CL represents CAS delay, TCK represents system clock cycle time, and tAC represents access time from CLK). The brand of memory particles is not the brand of memory, but the brand of particles used, so the final quality of memory particles of the same brand is different because of the processing of different manufacturers.

2) 2) The quality of PCB. The quality of the circuit board will have a great influence on the compatibility between the memory stick and the motherboard. If the compatibility is not good, it will easily lead to unpredictable results such as system instability and crash. Good PCBs are mostly 6-layer boards, which make them have good stability and heat resistance, while the quality of 4-layer boards is poor. And the wiring on the PCB board is also very particular. If the PCB of a memory is covered with small holes connecting one board with another, the quality of the memory is probably not very good.

3) Manufacturing technology of memory. This is what we can see with our eyes. The key is whether the solder feet of the chip and PCB are full and tidy. The quality of a memory can also be seen from these details, such as whether there is any welding residue, whether SPD and resistor are welded neatly.

The SDRAM of -7ns can work at the external frequency of 133. At present, -7ns SDRAM is everywhere on the market. In fact, among the SDRAM printed with the word -7 in the computer market, only the memory granule numbered KMXXXSXXXXBT-G7 from Samsung is the real 7ns memory granule, and the others, such as T7K and T7J from LGS, are 100 ns PC 100 SDRAM. The following is a serial number list of some collected real PC 100 SDRAM memory particles (INTEL certification), which is convenient for purchase.

Samsung 256M-64Mx4 KM44S64230AT-GL 9838

Samsung128m-16mx8km48s16030t9822

Samsung128m-32mx4km44s 32030t9825

Samsung 64m-8mx8km48s8030bt-gl801

Samsung 64m-4mx16km416s4030bt-gl807.

Samsung16m-2mx8km48s2020ct-gles807

Hyundai128m-32mx4 hy57v1294020 9824

Hyundai 64m-4mx/KOOC-0/6HY57V65/KOOC-0/620A TC-/KOOC-0/0P9803

Hyundai 64m-4mx16HY57V651620A TC-10S9805

Hyundai 64m-8mx8HY57V658020ALTC-10P9749TAK0021E

Hyundai 64m-8mx8HY57V658020A TC-10S9805

Hyundai16m-2mx8hy57v168010ctc-10p9807

Hyundai16m-2mx8hy57v168010ctc-10s9801ta.

LGS 64M-4mx 16 gm72v 66 164 1C T-7J 9806

LGS 16M-2mx 8 gm72v 1682 1D T-7K 9809

LGS 64M-8mx 8 gm72v 6684 1C T-7J 9748

Toshiba128m-8mx16tc59sm716ft-80 9838

Toshiba128m-16mx8tc59sm708ft-80 9835

Toshiba 64m-4mx16tc59s6416bft-80 9806

Toshiba 64m-8mx8a56877 9750kbdtc59s6408bft-80

Genesis16m-2mx8gs148c2m8a109NJ40

Siemens 256M-32Mx8 HYB39S256800T-8 9837

Siemens16m-2mx8hyb39s16800ct-8c9822

Siemens 64M-8Mx8 39S64800AT 98 12

Siemens 64m-4mx16HYB39S64160AT-8 9830

Hitachi 64M-8Mx8 HM5264805TT-B60 9748

Hitachi 64m-4mx16HM5264165tt-B609751

Fujitsu 64m-8mx881f64842b-103fn9750k01r1

Fujitsu16m-2mx8mb81f16822b102fn9810.

Fujitsu 64m-4mx1681f 641642b-103fn9805moo

NEC 64M-8mx 8d 456484 1 G5-a 10-9JF 98 12

NEC 64M-4mx 16d 4564 163 G5-a 10-9JF 9803 e 900 1

South Asia16m-2mx8n56V1680A0TESE73600302A47NJ19

OKI 16M-2mx 8 m56v 16800 e-8TS 98 16

OKI 64M-8mx 8 md56v 62800 a-8 98 18

TI 64M-8mx 8 tmx 6648 14a 8 1A7ET

TI 16M-2mx 8 tmx 6268 12 bdge 5m 82a 1 to P

IBM 64M - 8Mx8 0364804CT3B-260 9830

NPNX 64M-8mx 8 nn 5264805 TT-B60 9822

mosel-Vitelic 64M-8mx 8 v54c 365804 vbt 8 PC 9832

Mitsubishi 64m-8mx8m5m4m4v 64s 30atp-8 806

Mitsubishi16m-2mx8m54v16s30dtp-8811

Mitsubishi 64m-4mx16m5m4v 64s 40atp-8810

When selecting memory, you can refer to the models listed above and check the serial number of memory particles to see if it meets the PC 100 specification. The laser lettering on the surface of the memory should be clear, and the serial numbers on the same memory stick should be consistent without any traces of polishing. To exceed the external frequency of 100MHz, it is best to choose true 7ns or 8ns memory. At present, the memory of -7ns or -8ns on the market is actually 10ns, and both -7ns and -8ns are more expensive.