home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Creative Computers
/
Creative Computers CD-ROM, Volume 1 (Legendary Design Technologies, Inc.)(1994).iso
/
text
/
hacks
/
no_14mhz
< prev
next >
Wrap
Text File
|
1994-11-17
|
3KB
|
68 lines
Article 10079 of comp.sys.amiga.tech:
Path: torag!geac!censor!utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!zaphod.mps.ohio-state.edu!ub!uhura.cc.rochester.edu!rochester!kodak!sisd!jeh
From: jeh@sisd.kodak.com (Ed Hanway)
Newsgroups: comp.sys.amiga.tech
Subject: Re: 14MHz speedup
Keywords: Does it work on A2000?
Message-ID: <1990Nov17.153635.14348@sisd.kodak.com>
Date: 17 Nov 90 15:36:35 GMT
References: <1344@ewu.UUCP>
Sender: news@sisd.kodak.com
Organization: Printer Products Division Eastman Kodak
Lines: 52
In article <1344@ewu.UUCP> mpierce@ewu.UUCP (Mathew W. Pierce) writes:
>I just Dloaded the 14MHz speedup file by Leslie Ayling(s?) and was wondering
>whether or not it will work for the A2000? It is supposedly meant for the
>A500, but she says that it will work on other machines.
I've seen this speedup "design" and I'd be surprised if it works on _any_
machine. [For anyone who hasn't seen the design, it runs the 28MHz clock
through a a D flip-flop configured as a divide-by-2 and runs the resulting
14MHz clock into the bent-up clock pin of the 68000 instead of 7MHz.
That's it.]
A few weeks ago Dave Haynie posted a comprehensive description of why this
has little chance of working, and it boiled down to:
1) Any accellerator must access normal Amiga RAM, ROM, custom chips,
expansion devices, etc., with the same timing as a 7MHz 68000,
synchronized with the master 7M clock.
2) The 8520 Peripher Interface Adapter chips use the M6800 (yes,
68-hundred) interface, which requires a 0.7MHz E clock, and
VMA and VPA signals synchronized to it.
There are other problems with this particular design that diminish what
little faith I have in it:
1) It refers to the MC68000P12A as a 16-MHz part. My Motorola
data books say this should be a 12.5 MHz part. (It has a
fair chance of running at 14.3MHz, if you're lucky.)
2) The schematic diagram includes a switch on the clock signal
to switch between 14MHz and 7MHz. Now assuming that the
switch is mounted so it sticks out of the case, what we have
here is a (relatively) long, unshielded wire carrying a
high-frequency signal. We EE's have a technical term for
this -- it's called an antenna. :-) The amount of RFI that
it must generate and/or pick up must be incredible.
3) It mentions something about floppy drives stepping too fast,
so the author replaced his with one with that can handle a
5ms track-to-track step rate. I thought that the normal Amiga
step rate was about 3.6 ms, and any 3.5" drive should be able
to handle 3ms.
>Isa this a smart thing to do even if you do it right?
As you might guess, I think that to "do it right" you should start with a
better design.
--
Ed Hanway --- uunet!sisd!jeh
Use other side for additional listings. Some assembly required.
Any resemblance to real persons, living or dead, is purely coincidental.