Modifying microcode
Camiel Vanderhoeven
camiel.vanderhoeven at vmssoftware.com
Wed May 30 09:34:26 CDT 2018
The microcode for the MicroVAX 2 (for which the MICRO2 assembler was used) and the CVAX (which is the CPU in your 3800) is implemented as a mask ROM on the CPU chip itself. No way to change it, and no way you can use MICRO2 to assemble the microcode for the CVAX.
On 5/30/18, 3:19 PM, "cctalk on behalf of Kyle Owen via cctalk" <cctalk-bounces at classiccmp.org on behalf of cctalk at classiccmp.org> wrote:
Has anyone attempted to reassemble and update the microcode on a MicroVAX?
Seems like there's enough stuff here to possibly do it:
http://simh.trailing-edge.com/semi/ucode/
I'm thinking about trying to find a microcoded architecture to play with
before I design something around the Intel 3000 series.
I've got a MicroVAX 3800, so I suppose I could run MICRO2 to assemble the
aforementioned microcode. But then what? I assume PALs would have to be
burned to implement the new microcode. Or is it more complicated than that?
I don't have a PDP-11/60, unfortunately. I do have an 11/45, though...so
with this modification, I suppose one could have some fun:
http://repository.cmu.edu/cgi/viewcontent.cgi?article=3241&context=compsci
Thanks,
Kyle
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