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

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