# Reading SIMM modules markings

I have in my possesion a bunch of 72-pin SIMM modules that are not used anymore and I would like to use them again. Just placing them in some of my 486 computers yelded some strange  results. I KNOW the modules are good because I was the one that took them out of working computers.

The problem I want to solve is this:

looking at the writting on the chips, I want to know if there is a way to determine what kind of SIMM modules are they. For example:

one SIMM has:

72 pins, tin contacts,
chips on one side only,
there are 8 chips in 2 groups of 4,
on each chip there are three lines of text:

9410 K  USA
MT4C4001JDJ
-6

so ... what does this mean? Is there a site on the Internet that can be used to find out the answer?

Thank you.
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Commented:
In your example this should be a 4 Mb chip of 60ns no parity. The number MT4C4001JDJ if one look at the number 4001 this probably means 4001 kbit this times 8 (chips) divided by 8 (Number of bits per byte) equals 4 Mbyte.

This is not easy to know. There are some General guidlines. But there are no Rules!!!

The size:
A single sided chip is normally a 4 or 16Mb (or 64, not too sure) A double sided chip is normally (2, never seen one), 8 or 32 Mb (although I have seen double sided  16's...) this depends on what chips are used. Some normal numbers (Hidden within other digits and letters like seen in your example) are 100x, 400x, 4400, 8160, 17400 thise number usually equals the number of kbits this chip is built for an this times the chips devided by 8 is the number of kbyte the memory can handle I have also seen number like 2M, 4M and 8M this is normaly the Mbits istead.

Number of chips in the SIMM. If it is 8 it is probably normal, no parity. If it is 9 (or sometimes 12 when 4 of the chips are different from the others) this is probably a parity memory. This is per side of the memory. Newer memory sometimes only have two large chips (Or 4 if doublesided) these ar nomaly no parity. If found 1 (or somtimes 4) smaller chips along with these 2 large this is probably a parity mem.

Speed. '-60', '60' Or '-6' normaly means 60ns and '-70', '70' or '-7' normaly means 70ns and so on. Be careful if you find somthing like -12 it might be 12ns (if this is a quite new memory) or 120ns (Normaly found on old 30pins) likwise -10 and so on....

Hope this will get you somwere.
//Yin
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Author Commented:
Thanks, you explanations are usefull but ... for example, the manufacturer of the chip that has the code I mentioned in my question, mast have a "list" of all the chips they make and a description, same with the one that made the SIMM. If one could have access to such a list, this would eliminate the guessing work. Do you know of such a list? Is there a list of chip manufacturers and/or a list of SIMM manufacturers?
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Commented:
Sorry but to my knowledge there is no such lists easy available. There should be information about it but based on the guidelines above I have managed to do without. One could allways try to contact the manufacturer of the SIMMs or the Chips but I doubt that you will get hold of a 'universal' list for most of the manufacturers. I still think that the fastest/easiest way is to do this 'guesswork' and simply try them in the computer.

All SIMMs does not work in all the computers it should. ie: Even if it is a parity mem and it is req by the computer 'that' specifc SIMM might not work in that specific computer anyway.

//Yin
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