Re: Dynamic RAM / memory expansion

From: john/lori (
Date: 2001-01-19 18:53:38

> Another problem is the 72 pin SIMM. It has a 32 bit wide bus. Nice if you
> have a 486. But the 65xx is 8 bits wide. Is it possible to select just 8
> bits?

I would think so.  The actual chips are generally in a matrix
which is decoded with the /RAS, /CAS lines, with individual
8 bit slices of the 32 bit word having their own /CAS lines.

from the TM497MBK36A, TM497MBK36A 4194304 by 36-bit
data sheet:

DQ0-DQ7, Q8    /RAS0  /CAS0
DQ9-DQ16, Q17  /RAS0  /CAS1
DQ18-DQ25, Q26 /RAS2  /CAS2
DQ27-DQ34, Q35 /RAS2  /CAS3

(there are only two /RAS lines)

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