From: Dale_Adams@gateway.qm.apple.com (Dale Adams)
Newsgroups: comp.sys.amiga.emulations
Subject: Re: EMPLANT for 1200?
Date: 7 Jan 93 13:18:47 GMT
Organization: Apple Computer Inc.

In article <jdrew.0n5j@cryo.rain.com> jdrew@cryo.rain.com (Jim Drew) 
writes:
> I have a MAC II (68020) and several MAC IIx/cx's (68030).  Speedometer
> v3.1 overall performance (both same hard drive type and brand, purchased
> at the same time) is 4-5 times faster on the MAC IIx/cx over the MAC II.

I still assert that there is something seriously wrong with your Mac II 
setup.  You stated previously that you were only getting Mac II 
performance improvements of 10% or so over a Mac Plus.  This is patently 
ridiculous.   The only way this could happen is if you have something 
really screwed up on the Mac II.  Again I ask: what actual numerical 
results that Speedometer 3.1 is giving you for the Mac Plus, Mac II, and 
Mac IIx.

> You can't possibly be telling me that an 030 is only 10-20% faster than
> an 020???  This is simply not true.  The 030 (with it's DATA cache on) is
> substantially faster than an 020.

Yes, that's exactly what I'm telling you.  This _is_ true.   In fact, the 
performance delta is really only about 10%.  The '030 data cache is simply 
too small to make much (i.e., about 5-10%) of a difference in performance. 
Motorola's own data supports this.  Motorola has available a 68K family 
performance analyzer application which provides relative performance 
numbers for various 68K family processors.  When similary configured and 
at the same clock speed, Motorola's data shows the '030 is from 1 to 20% 
faster than an '020.  The average performance delta is 10%.  (For this 
comparision, both processors were run at 16 MHz, the '030 was set to 
bursts [the '020 can't], and all caches were enabled.)

> I never use the lower case version of MAC because could be considered to
> be a trademark.  I use 'MAC' deliberately.

True, "Mac" is trademarked by Apple.  No one else in the world seems to bother with this in their network posts, however.

> The system overhead that I am talking about does indeed exist.  I have
> spent over a year dissassembling and documenting the MAC II ROMS
> (versions 1.0beta->1.4) and I can tell you anything that you would like
> about how the MAC works.  The biggest overhead came to be in the form of
> System 7.0.  Run Speedomemter under System 6.0.7 and then run it under
> System 7.0.0-->7.1.0 and you will a 5-10% slowdown.

No argument about the Mac system software versions.  The ROM overhead 
simply isn't nearly that large.  There's something else in your system 
that's causing this.

> BTW, did you know that Apple actually checks (under System 7.0+) for the
> presence of RAM based ROM code.  They purposely write to the ROM base
> with data from the clock to trash RAM based ROM images (like EMPLANT,
> AMAX, and now SpectreII)?

It's true that Mac system software writes to the ROM space.  However, I 
don't believe it's for the reason you stated.  One of the Apple ROM guys 
told me the reason once, and that wasn't it.  I'll check back with him to 
find out why ROM writes are done.

- Dale Adams
Newsgroups: comp.sys.amiga.emulations