Due to various reasons, counterfeit and shoddy memory products are becoming more and more popular. How can we buy high-quality memory? That requires us to have a pair of "sharp eyes"... This article will focus on the popular SDRAM on the market.
1. How to identify memory from the chip number
When you see a strange memory, how do you know its capacity, speed, production date and other important parameters? Let’s take Samsung memory as an example:
First of all, the module capacities are: 16Mbit, 64Mbit, 128Mbit, 256Mbit.
Number: KMXXXXXXXXXXX-XXX
123456789101112
1. KM means Samsung memory
2. Type of RAM, 4=DRAM
3. Memory chip composition: 4=x4, 8=x8, 16=x16
4. S=SDRAM
5. Memory chip density: 1= 1M, 2=2M, 4=4M, 8=8M, 16=16M
6. Refresh: 0=4K, 1=2K, 2=8K
7. Memory ranking Number: 2=2 rows, 3=4 rows
8. Memory interface: 0=LVTTL, 1=SSTL
9. Memory version: blank=1st generation, A= 2nd generation, B=3rd generation
10. Package type: T=TSOPII (400mil)
11. Power supply: G=automatic refresh, F=low voltage automatic refresh
12. Minimum access cycle (highest frequency): 7=7ns (143MHz), 8=8ns (125MHz), 10=10ns (100MHz), H=100MHz@CAS value is 2, L= 100MHz@CAS value is 3
Let’s explain. KM416S16230A-G10 refers to Samsung 16M*16=256Mbit SDRAM memory chip, refresh is 8K, memory Banks is 3, memory interface LVTTL, 2nd generation memory, automatic refresh, speed is 10ns (100MHz). Other brands of memory can be roughly deduced in the same way...
2. What is the real PC-100?
After that, we need to understand some principles. Today, when the 100MHz bus is popular, choosing a high-quality memory to match the system can effectively improve the performance and stability of the system. The price difference between ordinary 10ns memory and PC-100 memory on the market is not big now. Since we have spent a lot of investment to choose a 100MHz system, I think there is no need to sacrifice performance in order to save dozens of dollars, especially if we want to exceed 100MHz. friends above. However, not all the memory labeled PC-100 on the market is "real" PC-100 memory. How should we, as consumers, identify it?
First of all, we must be clear that PC-100 memory is not a 10ns memory chip plus SPD, although 10ns memory can also run a 100MHz FSB. The PC-100 specification is a set of guidelines developed by Intel in order to cooperate with its BX chipset and enable various computer accessories to work stably and effectively at a 100MHz bus speed. It is now supported by all major PC accessory manufacturers. In this specification, in addition to the requirement that the clock cycle (ClockCycleTime) is not greater than 10ns, there are many other requirements for memory chips, such as the access time (AccessTimefromClock) is not greater than 6ns, CASLatency is 2 or 3, etc. Only memory that fully complies with the Intel PC-100 specification is "real" PC-100 memory.
There is a point that needs to be corrected here. Some people think that when the motherboard clock frequency is set to 100MHz, and the CAS is set to 2 in the motherboard BIOS option, the SDRAM that can stably work synchronously with the motherboard FSB (100MHz) is the real PC-100SDRAM. . In fact, under the 100MHz FSB, a CAS of 3 is also in line with the PC-100 specification. Moreover, when the CAS is 2, the performance is only a few percent higher than when the CAS is 3, so you don't need to care too much.
3. Practical identification method
Practice is the only criterion for testing truth. To correctly identify the memory, the most important thing is to look more and ask more questions. Let’s talk about the production process first. Some criminals actually reassembled the chips on some "junk" boards. This kind of inferior memory module not only has different thicknesses of printed circuit boards, but also has rough workmanship, uneven edges, and sometimes burrs. The solder joints and printed words on the chip are particularly blurry and rough. Once a buyer discovers that the memory stick is a combination of chips of different models (or different manufacturers, different speeds, and different dates), it must be a fake product. The quality of these memories is not up to par and can be identified with a little care.
Let’s talk about Remark. The so-called Remark is to polish the product logo on the chip so that low-speed products can wear high-speed clothing. Needless to say, when the frequency is high, the flaws will naturally be revealed. Nowadays, there are many unscrupulous processors. Their level of counterfeiting is very high. It is difficult to tell the authenticity with the naked eye. However, you can make the product run above the nominal frequency. Low-quality memory cannot withstand this test.
Finally, let’s talk about price. Price is the only competitive advantage of counterfeit and inferior products, so when you buy, do not try to get a bargain (haha, of course, it is also best not to be "slaughtered" by high-priced profiteers). This is what electronic products are like, you get what you pay for. In markets like Zhongguancun and Shenzhen SEG, price competition is almost fierce. The price difference for a memory of one specification and capacity rarely exceeds 10 yuan. If you find that the memory sold at two places differs by dozens of yuan, the cheaper one... humph, there is probably something wrong with it.