Legacy apps in Windows/OS X was Re: Old MS-DOS & Win Software

[Chuck Guzis]

On 12/8/2005 at 9:49 PM Allison wrote:

>>
>>Subject: Re: Legacy apps in Windows/OS X was Re: Old MS-DOS & Win
Software
>>   From: woodelf <bfranchuk at jetnet.ab.ca>
>>   Date: Thu, 08 Dec 2005 19:30:35 -0700
>>     To: General Discussion: On-Topic and Off-Topic Posts
><cctalk at classiccmp.org>
>>
>>
>>What I do find odd that the 8086 came out first then a few years later 
>>the 8088.
>>It still think the 8086/8086 could have had two instruction sets -- 
>>8080  emulation and
>>a better 16 bit design.
>
>Not that I know of.  I remember being able to get 8088s before the 86s
>and that was back in 78 or early 79.

I think you're thinking of the NEC V20/ uPD70108 and the V30/uPD70116 CPUs.
 Plug-compatible with the 8088 and 8086, but with a couple of instructions
added to switch modes into 8080 emulation. Overall, emulation was pretty
good, but should have been Z80 instead of 8080 and there were a couple of
small bugs in the emulation that weren't fixed.

Most vendors used the V20/V30, however, because they were low-power CMOS.
They also implemented some of the 80186 entensions, like ENTER and LEAVE
and PUSHA/POPA and multi-bit immediate count shifts like SHR AX,5.  If
you've got an old 8088/8086 box and need to run some code compiled to use
the 186/286 extensions, the V20/V30 is a very neat drop-in solution.

Cheers,
Chuck


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