- 4MB modules:1Mx32, 1Mx36
- 8MB modules: 2Mx32, 2Mx36
- 16MB modules: 4Mx32, 4Mx36
Identifying Your Memory Chips
The purpose of this guide is to help you identify and decide what type of memory your system requires. Here you will find graphics, a part-number table, and explanations to help you. If you are unsure of anything, please feel free to contact us with any questions you may have.To order new or replacement memory chips, we need to know (in order of importance):
1. The Part Number of Your Chips
2. The Speed of Your Chips in Nanoseconds
3. The Package Type (or Style) of Your Chips
4. How Many Chips You Are Currently Using
5. How Many Empty Memory Slots You Currently Have
Once you have this information you are ready to request a quote by email at vc@dejanet.com . Because memory prices can change on a daily basis, we will give you a current price quote via e-mail or a return phone call. In most cases, you'll have a quote within 24 hours or less.
1. Chip Part Numbers
This section will help you decipher what the markings on your memory chips mean. Memory chips are usually mounted on various kinds of modules, like SIMMs, which are designed to work in computer systems. Often the memory module as a whole will have a part number, and the memory chips that are mounted on the module will have different part number(s). To receive a quote for memory you would like to purchase, the chip part number (not the module part number) is by far most important. The chip part number, along with the number of chips per module, allow us to determine the function and capacity of memory.Memory chips tend to have 2 or 3 lines of text on them that include a part number, speed, and date code. Most part numbers start with a two or three character abbreviation that identifies the manufacturer, such as HM (Hitachi), M5M (Mitsubishi), TMS (Texas Instruments) or MT (Micron Technology).
The numbers (and sometimes letters) that follow describe the memory configuration of the chip, for example HM514400 is a 1Mx4 configuration.
After the part number, there is usually a "A", "B", "C", or "D." This is how some manufacturers grade the performance of the memory, with "A" being most superior and "D" least, e.g. HM514400A. Manufacturers normally have very stringent requirements on all the memory they produce, so all grades should perform equally well in personal computers. Also, be aware that some manufacturers, especially Micron and Texas Instruments whose part numbers almost always end in "DJ", do not use a letter to grade their parts.
In many cases, there will be an additional letter that codes the package type of the memory, e.g. HM514400AS. In this example, "S" stands for SOJ-type packaging.
2. Speed
Speed of the memory is an important factor that helps determine market value. Carrying over from the previous example, a 70ns chip may be encoded at the end of the part number, e.g. HM514400AS7. In this case, the "7" stands for 70ns. Sometimes there is a dash before the speed marking, e.g. KM44C1000AJ-7, and other times the speed is printed on a line above or below the part number. If the speed is printed on a separate line, a dash usually precedes the speed number. For most common memory chips, speed ranges from 50ns to 200ns. The trailing zero is commonly left off, so you may see "-6", "-7", "-8", "-10", or "-12", which represents 60ns, 70ns, 80ns, 100ns, and 120ns respectively.On most chips, there is a date code printed above or below the part number. The date code indicates when the chip was made, most typically in a year and week format (such as 9438 for the thirty-eighth week of 1994). Often, the decade's "place" will be left off. For example, 438 may also represent the thirty-eighth week of 1994.
Common Part NumbersTo ease readability, the table lists part numbers without speed or grade information. The real chip part numbers will look a little longer. A couple of examples of 1Mx4's: "HM514400ALTT7", or "KM44C1000AJ-7 |
||||||
| 256x4 | 1x1 | 1x4 | 4x1 | 4x4 2k | 4x4 4k | |
| Hitachi | HM514256 | HM511000 | HM514400 | HM514100 | HM5117400 | HM5116400 |
| Samsung | KM44C256 | KM41C1000 | KM44C1000 | KM41C4000 | KM44C4100 | KM44C4000 |
| Mitsubishi | M5M44256 | M5M41000 | M5M44400 | M5M44100 | M5M5117400 | M5M5116400 |
| NEC | 424256 | 421000 | 424400 | 424100 | 4217400 | 4216400 |
| Toshiba | TC514256 | TC511000 | TC514400 | TC514100 | TC5117400 | TC5116400 |
| TI | TMS44C256 | TMS4C1024 | TMS44400 | TMS44100 | TMS417400 | TMS416400 |
| MicronTech | MT4C4256 | MT4C1024 | MT4C4001 | MT4C1004 | MT4LC4M4B1 | MT4LC4M4A1 |
| Hyundai | HY534256 | HY531000 | HY514400 | HY514100 | HY5117400 | HY5116400 |
Most major chip makers use part number schemes like those above, where information about the chip is more or less encoded in the part number. However, some IBM part numbers follow a less self-explanatory scheme. Older IBM part numbers generally follow the pattern: NNLNNNN (where "N" is a number, and "L" is a letter) as in 89X8922 or 02G2871.
3. Chip Packages
SOJ or Small Outline J-lead.
By far the most common package type is the SOJ. SOJ chips come in three
different sizes: 300, 350, and 400 mil. The mil size actually refers to
the width of the chip in thousandths of an inch. All other things being
equal, the same chip in a larger package tends to have less market value.
TSOP or Thin Standard Outline Package.
A more modern but less commonly seen chip package is the TSOP. TSOPs are
very thin, compact packages that take up a minimum of space. While their
small outline shows how dense memory can be made, TSOPs are more likely
to be susceptible to physical damage from rough handling. TSOPs come in
300 and 400 mil sizes.
DIP or Dual Inline Package.
The DIP was more widely used before the SOJ became the favored package
type. DIP leads often go through the PCB board, in contrast with the surface
mounted SOJ and TSOP. DIP leads are sometimes trimmed, which can reduce
the market value of the part.
ZIP or Zigzag Inline Package.
The ZIP is also commonly seen on older memory products. They are also favored
in applications where board space is limited. As with DIPs, ZIP leads are
often trimmed to fit. This may reduce the resale value.
PLCC or Plastic Leaded Chip Carrier.
The PLCC is typically only seen in lower capacity configurations, usually
256kx1 or more rarely 1Mx1. It is distinguished by having leads on all
four sides.
Modules
The two most common types of memory modules are the 30 pin and 72 pin Single Inline Memory Modules or SIMMs.
30 Pin SIMM.
The most common varieties of 30-pin SIMMs are 256kx8, 256kx9, 1Mx8,
1Mx9, 4Mx8 and 4Mx9 although 16Mx8 and 16Mx9 are also possible. You will
typically find either 2, 3, 4, 8, or 9 memory chips on 30-pin SIMMs. Any
given 30-pin SIMM is likely to be populated with identical memory chips,
except the 3-chip SIMM. 3-chip SIMMs are likely to have 2 chips of the
same type, and a third parity chip which is different from the other two.
72 Pin SIMM.
The most common varieties of 72-pin SIMMs are
Other SIMMs
Less common simms include 40, 64, 68 and 80 pin SIMMs. The 64 pin SIMM looks like a smaller 72 pin SIMM and is easily confused for one. Some 64 pin SIMMs function like 30 pin SIMMs while others function like 72 pin SIMMs.DIMM or Dual Inline Memory Module
Some recently designed higher-end comptuers use DIMMs, which are often 168 or 200 pin. DIMM's (or SDRAM) is generally much faster than SIMM's. Currently, there are two main styles of DIMM's available - 66MHz and 100MHz. All new computer systems built by Virtual Concepts come with DIMM's installed.SIPP or Single Inline Pin-leaded Package
Many older personal computers and workstations used SIPP memory, which look like SIMMs with pins instead of an edge connector. This design was not as well received as the SIMMs because the pins tended to bend or break easily.Home
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