On 11 May 00, at 12:43, Bob Wright wrote:

> At 11:17 AM 05/11/2000 , you wrote:
> >I am working on a  old 486 board. This was one is probably circa 95-96 and
> >has a AMD486DX100  in it. There are two 72 pin simms  being used and four
> >30 pin simms slots unused. As I recall dual simm slots and pin adaptors
> >were pretty common back then so that users did not have to get rid of their
> >old 30 pin simms.
> >
> >Does anyone recall if it was common to use both 72 and 30
> >simultaneously...or were there particular requirements that had to be met?
> >....or was it depends on the board ? What were the issues ?
>
> It usually depended on the motherboard, the manual for the board will
> give you instructions on how to fill the slots, (you should be able to find
> the manual on the manufacturers web site).
>
> Those boards allowed for one 72pin simm in a slot, but the 30pin simms
> must be in matched sets of two each.

  Whoops.  72-pin SIMMs are 32/36 bits wide, but 30-pin are only 8/9
bits wide.  All 486es except the 486SLC model (386SX replacement)
need 30-pin SIMMs to be in sets of FOUR.

  On *some* 486 motherboards with both sizes, the four 30-pin slots
are mapped to the same "bank" as one of the 72-pin slots, and so one
can use one or the other, but not both.

David G

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