deciphering memory chips

From: Pete Turnbull <>
Date: Mon Jan 26 16:38:25 2004

On Jan 26, 11:41, Teo Zenios wrote:
> What's a good online resource to figure out what type of memory chips
you have?

Usually, Google. I didn't find any hits for KM428C25J-6 or KM428C25J
or KM428C25 or ... but I did find some for KM428C256 (which makes more
sense, actually).

The other thing I use is a fairly large collection of data books.
 Never discard data books :-) And I just happen to have a Samsung 1994
Product Guide that lists the KM428C256. Being only a Product Guide, it
doesn't give details, but it says its a 2Mbit device organised as 258K
x 8, and there are several speed variants as well as a V256, and

KM is Samsung. 4 means DRAM, 42 means VRAM. 8 means 8 bits wide. C
means 5V CMOS, V means 3.3V CMOS. 256 is the density and organisation,
in this case 256K Page Mode. 257 means "E/F" mode (I can't think what
that stands for, off the top of my head). J means SOJ (P is DIP, Z is
ZIP, T is TSOP). The -6 means 60ns (-7, -8, -10 are also common).

> I have an old matrox Ultima + VLB card that has 2mb vram (consisting
> of 8 x KM428C25J-6 chips) and has 8 more sockets for 2mb more memory

As you probably know, VRAM is dual-ported RAM, so that the graphics
display hardware can read it without interfering with writes from the
graphics engine or CPU. This particular type is used in some old SGI
video systems.

> (the type where the chip pins are curled around and point to the
> bottom of the chip)

You mean like a PLCC but with pins on only two sides, sort of like a
DIL chip? It's called SOJ, or more specifically, xx-SOJ-y00, where xx
is the number of pins and y00 is the spacing between the two rows in
1000ths of an inch (so 300 means 0.3").

> Are these common chips? Most video cards I have seen either use dram
or edo ram.

I don't think so. But I'm not an expert on video cards.

Pete						Peter Turnbull
						Network Manager
						University of York
Received on Mon Jan 26 2004 - 16:38:25 GMT

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