MicroVAX 3300/3400

[Glen Slick]

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_Maintenance_Dec90.pdf
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."