> > > Not that I know off. The V20 did behave exactly like an 8088.
> > Besides, it wasn't a completely Bug-For-Bug replacement. NEC failed to
> > implement some of the quirks of the 8088. For example, if an interrupt
> > occurred during the execution of an instruction with a double prefix, the
> > NEC would continue, but the intel would drop one of the prefixes when
> > resuming.
> > REP MOVSB DS:[SI] DS:[DI]
> > will resume with a V20, but with an 8088 will only do one more rep after
> > an interrupt.
On Wed, 12 Mar 2003, Hans Franke wrote:
> Well, that's eactly the 186 behaviour. Now considering that the
Not MY experience. The 386 is the first Intel that I'm aware of that
fixed the double prefix bug. But NONE of the NEC v series had that
bug. (ONE way to tell whether the current chip was Intel or NEC)
> timeing was also exactly like 186 (or real mode 286), and the
> instruction set is the same, I still think NEC just used the
Did the V20 have the INSB/INSW/OUTSB/OUTSW instructions? (present in
80186/80188, but not 8086/8088
> 186 (188) core as template for the V20/V30 - Considering that
> V40/50 where like the 186 with integrated perhipherals, you
> may considere it as a two step knock off...
BUT,...
Other V20 instructions followed the 8088/8086 model.
Such as what happens if you push SP. For example:
MOV BX, SP
PUSH SP
MOV CX, SP
POP AX
; will copy the value pushed by PUSH SP into AX.
; on the 8088/8086 and the V20, AX will equal CX
; on the 80186/80188, AX will equal BX
(how to tell whether the chip is 8086/8088 v 80186/80188 or above)
NEC fixed some of the bugs, but not all. Some of them were the basis for
the decision in the Intel v NEC lawsuit.
--
Grumpy Ol' Fred cisin_at_xenosoft.com
Received on Wed Mar 12 2003 - 19:59:21 GMT