On 05/30/2018 11:48 AM, Paul Koning via cctalk wrote:
On May 30, 2018, at 11:11 AM, Camiel Vanderhoeven via cctalk
<cctalk@classiccmp.org> wrote:
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.
Didn't the 780 get its microcode loaded by the console LSI-11? And the 730
used bit slice processors (AMD 2901) as I recall, so that had to have its
microcode external.
The early 780 had most microcode in ROM, and had a small
writable control store for special OS-required options and
patches. Later machines had more WCS, but I think they
still had some non-writable control store. I remember our
early 780 had the WCS board replaced during a field upgrade,
and maybe the fixed control store was replaced, too.
Jon
