8088 vs. 80c88

[Chuck Guzis]

On 22 Feb 2009 at 18:54, bfranchuk at jetnet.ab.ca wrote:

> Well what are the bugs?

Here's the one with JRT Pascal (IIRC):

    LXI		SP,LABELX
    CALL	LABELX

LABELX:
    ...
    RET

crashes and burns on a V20.  Runs fine on an 8080/Z80. I may not have 
it exactly--this was over 20 years ago and it's going to take some 
digging to find my paperwork on the V20.  Until then, you'll have to 
rely on my ever-more-tenuous memory it or try it for yourself.

V20 emulation mode was enough of a problem that we eventually 
disabled it in 22NICE.  x86 machines were getting powerful enough 
that software emulation was faster anyway.  We could also do things 
in software emulation that we couldn't do in V20 mode, such as trap 
I/O accesses and redirect them to user-written servicers. 

My contact at NEC Natick was Rich Naro and he indicated that 8080 
emulation mode was very low on the "things to be fixed" list in the V-
series chips.  

There were also some very strange behavior when an 8087 was included 
into the mix.

Cheers,
Chuck