9 Dec
2005
9 Dec
'05
7:20 p.m.
Subject: Re: Legacy apps in Windows/OS X was Re: Old MS-DOS & Win Software
From: "Chuck Guzis" <cclist at sydex.com>
Date: Fri, 09 Dec 2005 11:00:19 -0800
To: cctalk at classiccmp.org
On 12/9/2005 at 1:35 PM Allison wrote:
Both. The address calc was on the wider bus so that it was not in a
critical path. You needed the busses inorder to do the cal with fewer
cycles and intermediate temp storage. The EA calc and the dual busses
were important when Intel went to court over it. There were distinct
differnces how they worked inside even though the socket was the same.
What I never figured out for sure was if the 8080 used current segment
or not. the differnce is the 8080 emulation would then be capable of
running as if there were N many (available ram/64k) differnt ram
areas making a banked 8080 possible. then again I never really looked at
that seriously enough to implement.
I added why it was faster. For the V20 in a XT
clone it was easily 10% and
for the V30 is was more..
Yes, but there the tech manuals and your explanation disagree. NEC seems
to think that the dual data busses were the big thing, but you mentioned
the EA calculation difference. Wonder which resulted in more performance
boost. On the other
hand there is a sorta improved Z80 like thing NEC did, the
ucom7800 series and they are interesting. Looks Z80 like but the
instruction set is anything but. I have a bunch of the PIGGYback
(78PG11) and romless 7800 parts.
Just look at the Rabbit 2000 instruction set. "Sort of Z80" is the best
way to describe it. Many additions and deletions. Before I programmed it,
I had two choices--either sit down with the manual and carefully note
differences or program it in C, the way Rabbit wanted me to. Suffice it to
say that the level of binary compatibility would be a serious barrier to
getting Wordstar running, if that was one's intent.