Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uunet!microsoft!alonzo
From: alonzo@microsoft.UUCP (Alonzo GARIEPY)
Newsgroups: comp.sys.handhelds
Subject: Re:  HP-48 Emulator
Message-ID: <53019@microsoft.UUCP>
Date: 9 Mar 90 03:42:36 GMT
References: <6724@hydra.gatech.EDU>
Reply-To: alonzo@microsoft.UUCP (Alonzo GARIEPY)
Distribution: comp.sys.handhelds
Organization: Microsoft Corp., Redmond WA
Lines: 25

> It might help to compare apples to apples...

A good point.  I will have to do actual instruction timings to confirm
the relative speed of the Saturn and x86 CPUs.  As was pointed out, it
is difficult to tell exactly what is meant by these MHz numbers.  If 
the Saturn does have a one bit memory bus, 1 MHz is very slow.  Perhaps
someone with all the facts can explain the CPU/Memory architecture of
the Saturn.

Since I have a 25MHz 80386 machine on my desk, the performance on a
286 doesn't concern me much anyway.  Intel is selling 386s below the 
286 price so that the AT can become a thing of the past and 32 bit
OS/2 can rule the land.

Since my emulator would by asynchronous (would emulate each instruction
as fast as possible) only average case performance is important, and parts 
of the ROM that rely on timing would need adjustment.

One of the tricks for improving average performance is coding commonly
called subroutines and idioms (e.g., 142, 164, 808C) directly in x86 
assembler.  Such tricks abound.  I would expect a 2 or 3 times speed
improvement in assembler over C even before applying tricks.

Alonzo Gariepy
alonzo@microsoft