[Feature request] NEC V20 support for XT machines

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AlecV
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Joined: Sun 12 Jun, 2016 8:37 pm

[Feature request] NEC V20 support for XT machines

Post by AlecV » Mon 25 Jul, 2016 2:45 pm

Is it possible to add a new CPU option for the XT-class machines: NEC V-20 ?
It was a popular upgrade for the IBM PC and clones since it was ~20% faster.
Moreover NEC V20 supported some additional commands like REP INS e.t.c.

Datasheet:
http://www.ceibo.com/eng/datasheets/NEC ... Manual.pdf

Commands:
http://phg.chat.ru/opcode.txt
(search "NEC")

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omarsis81
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Re: [Feature request] NEC V20 support for XT machines

Post by omarsis81 » Mon 25 Jul, 2016 10:13 pm

That would be great! And if it's fully emulated I would be eager to try the 8080 emulation mode

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SarahWalker
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Re: [Feature request] NEC V20 support for XT machines

Post by SarahWalker » Tue 26 Jul, 2016 6:36 pm

The 8080 emulation mode is largely why I've avoided the V20 so far.

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omarsis81
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Re: [Feature request] NEC V20 support for XT machines

Post by omarsis81 » Tue 26 Jul, 2016 7:43 pm

SarahWalker wrote:The 8080 emulation mode is largely why I've avoided the V20 so far.
I always thught it is very close to he x86 architecture...

AlecV
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Joined: Sun 12 Jun, 2016 8:37 pm

Re: [Feature request] NEC V20 support for XT machines

Post by AlecV » Wed 27 Jul, 2016 11:17 pm

JFYI, "fake86" emulator pretend to be a V20 emulator (as defined in cpu.c). But MSD (Microsoft Dosgnostic) determines its CPU as 80186.
https://sourceforge.net/projects/fake86/
It works for me. I need some 186+/V20 instruction (like PUSHA/POPA ans REP INS/OUTS) in the XT environment to test my specific software.

Full v20/8080 emulation may be difficult and requires special support software
http://www.vcfed.org/forum/showthread.p ... ss-machine

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