Modifying microcode

Tony Duell ard.p850ug1 at
Wed May 30 12:51:30 CDT 2018

On Wed, May 30, 2018 at 4:11 PM, Camiel Vanderhoeven via cctalk
<cctalk at> wrote:

>> Gotcha. Which small VAXes had external ROM/PALs for microcode store?
> Depending on your definition of small, the MicroVAX 1, and the VAX 8000 series
> (not that small). In both cases though, the ROM chips are a custom DEC design.

The 11/730 (one 10.5" rack unit for the CPU, heavy, but I can lift one
fully assembled)
has (most?) of the microcode in RAM, it's loaded from the TU58 when
you start the
machine. And apart from the ECC gate arrays, it's all standard ICs in
the CPU, albeit
with a _lot_ of PALs.


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