27 May
2021
27 May
'21
1:50 p.m.
On Wed, May 26, 2021 at 3:38 PM Jonathan Stone <kiwi_jonathan at yahoo.com> wrote:
two points:
1. MS650-AA 8mb modules from a KA650 will work in a KA640. They won't work with a
KA655 or a kA660 (or a KN210_. Those need the MS650-BA, or the 16MB MS650-BB, or the
third-party 32MB modules. So if your KA640 is dead and you want to upgrade, you will
likely need new memory, too. (You likely know this already.)
I've been wrong about that for several years. I have always assumed
that an M7621 MS650-AA 8MB memory board was compatible with all of the
M7620 KA650, M7624 KA640, M7625 KA655, and M7626 KA660 CPUs.
I didn't realize until now that an M7621 MS650-AA 8MB memory board is
only compatible with the M7620 KA650 and M7624 KA640 CPUs, and the
M7625 KA655 and M7626 KA660 CPUs are only compatible with the M7622
MS650-BA 16MB memory board (or the less common MS650-BB 8MB version of
the M7622).
Unless I am also wrong about this, the M7622 MS650-B memory boards are
compatible with all of the M7620 KA650, M7624 KA640, M7625 KA655, and
M7626 KA660 CPUs.
KA655 CPU System Maintenance, Order Number EK-306AA-MG-001
http://www.bitsavers.org/pdf/dec/vax/655/EK-306A-MG-001_655Mnt_Mar89.pdf
Page 1-4 (Page 15 of the PDF)
"NOTE: The KA655 CPU supports only the MS650-BA (16 Mbyte) memory
module. The MS650-AA (8 Mbyte) is not supported because of its slower
access speed."
KA660 CPU System Maintenance, Order Number EK-398AA-MM-001
http://www.bitsavers.org/pdf/dec/vax/4000/EK-398AA-MM-001_KA660_CPU_System_…
Page 1-10 (Page 20 of the PDF)
"1.4 MS650-Bn Memory Modules
The MS650-BA and MS650-BB memory modules are quad-height, Q22-bus
modules. Timing of the MS650-BA (16 MBytes) and MS650-BB (8 MBytes)
modules is dependent upon the KA660 clock speed and CMCTL.
The MS650-AA memory module may not be used with the KA660 system CPU."