> > > > Well, usualy this doesn't work, because of the different CPUs
> > > > (I assume we are talking about CP/M80 - CP/M86 will of course
> > > > boot on most classic PCs). The only way beside Emulators under
> > > > DOS/Win, and rare coprocessor boards is of course the NEC V20.
> > > > A V20 is for all PC/PC-XT machines a must, because of about
> > > > 10% faster execution (the V20 core is build like the 186/286).
> > > The problem with the V20 (and the V30, which IIRC is the '8086' version)
> > > is that you only get the 8080 instruction set. And while CP/M will run on
> > > an 8080, a lot of the more recent CP/M software needs a Z80.
> > Yep, you're right. It did quite work well with my
> > software. And IIRC he was talking about software
> > development for an IMSAI, and that's and 8080, if
> > not modified with a Z80 CPU board - which again
> > would be no IMSAI anymore :) So a V20 with the
> > 8080 mode is adequate.
> It can be argued that if it uses code not executable on an 8080, it's not
> really CP/M-80 software.
I wouldn't go that far. A Programm can rely on a CPU which is an
enhanced version of a 8080 (read can run unmodifiend 8080 code),
but uses CP/M-80 as operating system is still CP/M-80 software.
I guess the AT is the PC equivalent of a Z80 machine. You still
run the same MS DOS as on an 8088 XT, but some applications may
need a 286 to run.
> If you run an 8080-mode V20, you can run a BIOS written in 8086 code, which
> may offer considerable advantages over the 8080-only BIOS. What's more, if
> you do that, then you can incorporate ISA-bus cards into your S-100 system
> with an adapter, which can make development of a comfortable computing
> environment much easier. An example might be the video circuitry and
> keyboard. If you put an 8-bit ISA monochrome board on an S-100 card, you can
> then use the driver code in the PC BIOS (as in the printed listing in the Tech
> Ref) and you can use it pretty much independently of the CP/M system BIOS,
> since it will be called from the code to which control is transferred whenever
> there's a BIOS call. All the CP/M BIOS has to do is call the code that
> switches to native mode before interpreting the parameters of the call.
Jep. that kind of stub code is needed. But wheren't there some problems
when switching back ? It wasn't all easy.
> I've looked long and hard at this, having wanted to use a V50 (16-bits,
> enhanced execution unit, integrated peripherals, DMAC, PIC, UART)
As for the enhanced execution parts, the V20 and V50 are the same. Both
are from the CPU part like the 186 - or like the 286 sans virtual adressing.
> in the same
> way. Mounting a couple of 8-bit ISA cards on an S-100 board is quite
> straightforward, and the signals seem to work out quite well, too. The
> combination I'd use would be an 8-bit monochrome display board and an 8-bit
> HDC.
See, where is the idea of using an S100 bus system and tehn adding ISA
cards ? I'd rather take a XT clone, plug in a V20 and let the hardware
be standard (8 Bit) PC hardware - and MS-DOS as superior BIOS (Well, in
fact I belive MS-DOS is still one of the best, if not the best bootloader
avbailable).
Gruss
H.
--
VCF Europa 3.0 am 27./28. April 2002 in Muenchen
http://www.vcfe.org/
Received on Wed Apr 10 2002 - 14:20:10 BST