Date   : Mon, 18 Jul 1994 14:37:22 +0100 (BST)
From   : clr1@...
Subject: Re: Steve's emulators.

> I don't know if anyone is following some of the things I have been
> writing, but I am working on 2 emulators and am starting a third.
> Why?  Because they have completely different design architectures,
> and I particularly like my 2nd emulator's internal design, which
> holds my secret [now to be reveal] of *not* storing the Status
> Register anywhere!

Quite a nice trick - could be some hefty code though! I still prefer my 
method (which unfortunately you C-programmers can't do! ;-) of using PC 
flags for bits C and Z of the status register... that's really the only 
reason mine is faster (by about 20% or something) than SQs. Is there any 
chance of James testing his on a 386-40 so we can compare notes?

I have a bit of a problem which I think I could really speed up - how can 
I do relative branches? What I'm doing at the moment (basically) is:


 load branch distance byte
 if <branch distance> is less than 128
 move P back <branch distance>
 goto end
 move P forward <branch distance>
 .end

Is there a better way of doing this? In the 256^3 speed test this is *by 
far* where I lose my speed.

+-------------------+-------------------------------------------------+
| /-- |_| /-- | (~  | "And the driving is like the driving of Jehu,   |
| \-- | | |   | _)  | the son of Nimshi, for he drives furiously."    |
+-------------------+-------------------- Second Book of Kings 9 v20 -+