NEC V20 and Rainbow (was: NEC V-20 was: Native CP/M)

From: Mark Tapley <mtapley_at_swri.edu>
Date: Tue Apr 16 00:10:45 2002

Lawrence wrote:

> On the Rainbow I saw mention of either an EPROM mod (it's documented
>according to www.old-computers.com) or choosing the OS on start-up. I can't
>remember the boot-up choice on my 'bow and it's buried right now.

        Boot-up choice is made by telling the system which disk to boot
from. But you don't get to that choice unless you modify the boot PROM (I
think not EPROM) to account for the V20's faster (fewer cycles) execution
of a timing loop. The modification is documented, I think it's in Rainbow
News and I can dig it out in a couple weeks if anyone is interested.
        For purposes of the original thread, modifying a Rainbow is
needless, because it already includes a Z-80 (4 MHz) in addition to the
8088 (4.mumble MHz), and will run Dec CP/M-80/86. It probably makes a
pretty good platform for anyone wishing to cross-develop from MS-DOS (up to
3.10b) to CP/M.
        For hot-rodding purposes, the V-20 mod is recommended by Rainbow
News as a good way to get more speed out of the Rainbow.
                                                - Mark
Received on Tue Apr 16 2002 - 00:10:45 BST