20 Mar
2005
20 Mar
'05
6:07 a.m.
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!)
Thanks,
Ed
--
edward at groenenberg.net | Collector of PDP-11's.
http://www.groenenberg.net
Unix Lives! M$ Windows is crap.
'05 GSX-R1000
20 Mar
20 Mar
9:38 a.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.
7218
days inactive
7218
days old
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edward＠groenenberg.net -
mcesari＠comcast.net