Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!uakari.primate.wisc.edu!brutus.cs.uiuc.edu!apple!oliveb!amiga!cbmvax!daveh
From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga.tech
Subject: Re: speeding up the amiga and hardware hacking
Message-ID: <9303@cbmvax.commodore.com>
Date: 11 Jan 90 22:44:03 GMT
References: <140.filbo@gorn.santa-cruz.ca.us>
Organization: Commodore, West Chester, PA
Lines: 42

in article <140.filbo@gorn.santa-cruz.ca.us>, filbo@gorn.santa-cruz.ca.us (Bela Lubkin) says:
> X-Claimer: I >am< R Pentomino!

> In article <697@tau.sm.luth.se> Karl-Gunnar Hultland writes:
>>contact and a switch to XCLK enable and thus get a FASTER amiga.
>>If this works it would give faster custom chips too, and I'd like
>>that very much.

> I've asked about this before (not here) and never gotten a good answer.
> I'd like to hear from the real hardware gurus on this.  

You can go a little bit faster.  In order to work nicely with Genlock
devices, any Amiga will let you run a clock roughly 5% faster than the
basic 28.636MHz (NTSC) clock.  Genlocks use the XCLK and /XCLKEN lines
and may have some clock slop, but typically not much -- the color clock
is very frequency sensitive in video, so if you see color, you are
pretty close to dead on, frequency wise.  In any case, while there is
some slop, this isn't intended to be a general way to boost your system
speed.  Anything beyond 5% and you're just plain lucky if it works.  And 
of course, if you have some need for color composite video, just about 
any noticable speedup here will kill your color, though the monitors 
typically handle the slightly faster dot clock.

The other thing to be careful about is the clock quality.  The system
expects a nice TTL compatible clock applied to XCLK.  If you feed it
a noisy, analog, or unbalenced (duty-cycle-wise) signal, you have a good 
chance of creating a flakey system.  Some 68020 and 68030 boards may be 
more sensitive to this clock speed and quality than the main 68000 
motherboard, since most use a 14MHz clock of some kind.

> There's enough chance of damaging hardware to say: BE CAREFUL!

I'd certainly agree with that, as with any hardware hack.  Know what 
you're doing!

> Bela Lubkin    * *    //  filbo@gorn.santa-cruz.ca.us  CI$: 73047,1112 (slow)
>      @       * *     //  belal@sco.com  ..ucbvax!ucscc!{gorn!filbo,sco!belal}
> R Pentomino    *   \X/  Filbo @ Pyrzqxgl +408-476-4633 and XBBS +408-476-4945
-- 
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