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

From: Lawrence Walker <>
Date: Tue Apr 16 05:29:58 2002

 I would be interested in seeing the mod documentation when you find it. I
keep hoping I'll find a cheap stash of V-20s to use on about 3 or 4 of my
boxes, altho they come up fairly reasonable on EPay from time to time.
 Hows the Stylewriter project going ?


> Lawrence wrote:
> > On the Rainbow I saw mention of either an EPROM mod (it's documented
> >according to 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 - 05:29:58 BST

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