Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!asuvax!hrc!force!covertr
From: covertr@force.UUCP (Richard E. Covert)
Newsgroups: comp.sys.atari.st
Subject: Re: Mega chips & drive questions
Summary: Tiny board on 68000 in Megas
Message-ID: <4725b5fe.14a1f@force.UUCP>
Date: 30 Nov 89 15:13:58 GMT
References: <21653@brunix.UUCP> <5440088@hplsla.HP.COM>
Organization: gte
Lines: 39

In article <5440088@hplsla.HP.COM>, andyc@hplsla.HP.COM (Andy Cassino) writes:
> mjv@iris.brown.edu (Marshall Vale) writes:
> 
> |I have several questions about chips in my Mega2. 
> |
> |I also noticed that there was a very tiny board on top of the 68000 with a 
> |_SCST74LS74B1_ in it and a wire running to an unlabeled spot on the 
> |board just above and to the left of the 68000.  Anyone know what its for?
> | It seems like it was a rather last minute change and the glue job was
> | very sloppy.
> 
> Hmmm, my Mega has a similar kludge except the extra chip is piggy-backed on
> another small TTL chip. It's pretty sloppy, too. I assumed the dealer did
> this in the ROM upgrade, maybe not, eh?
> 


There has been quite a discussion on GEnie in Jim Allen's Fast Technology
Turbo16 Topic about just this subject. It seems that when Jim Allen came
out with the T16 various Blitters would fail at the higher speed. so,
for some Megas, you have to replace the Blitter. You should contact
Jim Allen at Fast Technology, or d/l the T16 Topic from GEnie.

Anyway, the tiny pc board attached to the 68000 cpu on SOME Megas to correct
a timing problem with some Blitters. It seems that Atari has more than one
source of the Blitters, and not all have the same timing characteristics.
So, some Megas have the little board to correct this. Again, I got this info
from Jim Allen of Fast Technology.

I would recommend that you get a GEnie account and contact Jim Allen there.
Jim is probably the most knowledgable hw hacker for the ST outside of the
engineers at Atari Corp.

I hope this helps someone out there.

P.S. I am a happy T16 owner myself. Jim has been a great support getting my
Mega ST working with his T16. Thanks Jim!

Rich Covert