20 Mar
2005
20 Mar
'05
12:38 p.m.
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.