Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!usc!zaphod.mps.ohio-state.edu!think!snorkelwacker!mit-eddie!rutgers!cbmvax!daveh
From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: 50 MHz MC68040 capabilities?
Message-ID: <9691@cbmvax.commodore.com>
Date: 15 Feb 90 15:51:06 GMT
References: <1129@mindlink.UUCP>
Reply-To: daveh@cbmvax.cbm.commodore.com (Dave Haynie)
Organization: Commodore, West Chester, PA
Lines: 37

In article <1129@mindlink.UUCP> a186@mindlink.UUCP (Harvey Taylor) writes:

> Who is going to produce the first Amiga 50 MHz '030 card?

>    Dave, is this clock feasible on the A2630? On any released '030 card?

In general, it probably can be done on existing cards, but it's certainly not a
simple drop-in.  There are three main problems.  The first of these is the
problem of clock quality throughout the board.  Lots of tweaking went into the
A2630's 25MHz clocking system to keep those fast clocks looking reasonably close
to what chips like digital clocks signals to look like all over the board.  When
you drop in a double-speed clock, all that nice tuning may not be so nice any
more.  So that's the first hurdle.

The second one will be any synchronous logic on the board.  Anything clocked off
the 50MHz clock will now likely go twice as fast.  Some things, especially memory
circuits, shouldn't really run that fast.  So some state logic may have to be
redesigned; if you're lucky, there's enough room left over in a programmable part
somewhere and no major hacking to the actual board will be required.

The last issue is component speed.  There's no DRAM yet out that can hope to 
keep up with a 50MHz 68030, even as well as the 100ns DRAM on the A2630 keeps 
up with the 25MHz 68030.  So some tweaking will be required to add wait states
to support even 60ns or 70ns DRAM.  Then there's the fact that lots of TTL
and PAL parts just don't work very well at 50MHz, so faster parts will have to
be substituted, if they exist.

Bottom line:  if I ever get a free week or so around here for some hacking, I
may try it on an A2630.  It won't be a piece of cake, but it'll probably be
possible.

>  Harvey Taylor      Meta Media Productions

-- 
Dave Haynie Commodore-Amiga (Systems Engineering) "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: hazy     BIX: hazy
                    Too much of everything is just enough