Path: utzoo!utgpu!water!watmath!clyde!rutgers!psuvax1!vu-vlsi!cbmvax!daveh
From: daveh@cbmvax.UUCP (Dave Haynie)
Newsgroups: comp.sys.amiga
Subject: Re: 68030 Questions
Message-ID: <3200@cbmvax.UUCP>
Date: 25 Jan 88 20:25:57 GMT
References: <494@.UUCP>
Organization: Commodore Technology, West Chester, PA
Lines: 43

in article <494@.UUCP>, alex@.UUCP (Alex Laney) says:
> Summary: What about the new '030 Card?

> [Don't have any reference for the '030 yet]
> 
> ...is the MMU on the Commodore 68020 card going to constrain the
> internals of Exec/Dos to not use the MMU on the '030. I doubt if it is
> compatible, but hopefully it does a subset, at least. 

The 68030's MMU is in fact a subset of the 68851 on the A2620 card.

> It sounds like another round of, well you can upgrade to the new CPU, but
> you can't use any of the features of it. You know, turning off caches, etc.,
> seems to be mandatory with the '020. 

Not at all.  The Amiga OS does in fact turn on the 68020 cache when it
starts up, and most things run without any trouble with the cache on.  A
few games are apparently running self-modifying code or something that
causes a problem with the cache, but most Amiga software runs fine.

> And the '020 really only speeds up with 32-bit memory, as well. 

Well, the A2620 runs our production line test a bit faster than the 68000
with it's on-board memory disabled.  It has going for it the cache, and
the fact that anything that's happening on-chip is still going to happen
at 14.3 MHz.  And 68881 performance goes up with the 68020's real coprocessor
interface.  But for plain old integer operations, the fast 32 but memory
helps alot.

> I hope that some of the lag time until the next OS release is used to look
> at these issues. I think everyone wants over time to upgrade to at least the
> '020, then the '030, [of course, the chips have to go down to $5 each :-)] so
> let's try to make the path less bumpy!

The '030 running with data cache enabled introduces the most problems.  Still,
many of these can be solved in hardware if the designer takes the time;
you really do want to use that data cache!

> Alex Laney   alex@xicom.UUCP   ...utzoo!dciem!nrcaer!xios!xicom!alex
-- 
Dave Haynie  "The B2000 Guy"     Commodore-Amiga  "The Crew That Never Rests"
   {ihnp4|uunet|rutgers}!cbmvax!daveh      PLINK: D-DAVE H     BIX: hazy
		"I can't relax, 'cause I'm a Boinger!"