Difference between M8728 & M8750

[Mike Cesari]

On Mar 20, 2005, at 7:07 AM, Edward wrote:

> Hi All,
>
> Anybody able to tell me the difference between the M8728 (11/70 MOS 
> memory board)
> and the M8750 (11/750 MOS Memory board) or why DEC decided to assign 2 
> numbers
> to it (the M8750 has this number stamped on the handle, but the board 
> bears
> the number M8728!)
>

An M8728 is 64K x 39 bits (256KB + ecc) and works in both 11/750 and 
11/70. The M8750
is 256K x 39 bits (1MB + ecc) and works only in the 750. The same PCB 
was used with
minor modifications and higher density DRAMs. DEC didn't always catch 
and/or care
about such details.

Mike

"minor modifications" (from memory) involves removing the extra power 
traces required
for MK4116's and adding the extra address lines for the 64Kbit chips.