Yes, I also bumped up a 386 (as well as 286's and my
Celleron 500 is running comfortably at 623...it was
unreliable at 625, but runs smoothly at 623)I've even
bumped up an old LCII and a IIsi Macs...But I ran into
instabilities once I went abote 10% on almost every
Mac overclock I attempted. I was able to aleviate this
by implementing a memory buffer circuit. With this, I
was able to clock these old macs to 3-4 times their
rated speeds...The reason is the memory mapping
technique that Apple uses. I'm no programmer, but I
heard from a programmer that Apple's map their memory
differently than almost any other computer...don't
know the specifics, but because the ram was soldered
to the board, you couldn't overclock without some kind
of buffer circuit for the memory. All of the intel
machines I overclocked needed faster RAM to get good
results. My Celeron is running CAS 3/133 ram...it
wouldn't run with the 100 ram! I suspect that in a way
you are correct, in that it may not affect the Newt
the same way, but I for one wouldn't attempt an
overclock without some thourough reverse engineering
to assure that the internal support components can
accomodate the increased clock speed! Otherwise, you
may end up having some timing problems with the main
CPU...
Of course, my hardware knowledge is at the level of
hobbiest, so I may be completly off base here due to
my lack of formal trainnig...this is just my trial and
error experience talking here!
Ed (walking in waters I wasn't trained in)
web/gadget guru
--- Jon Shurtleff <jon.shurtleff@munich.netsurf.de>
wrote:
> I don't think the upgrade board does anything but
> overclock the processor.
> The glue chips on the board are probably just to
> handle the switching
> between the two crystals by way of the power switch.
> My experience doesn't
> match what you've said. I've been overclocking
> computers for years and you
> rarely run into memory problems until you hit much
> higher overclock rates
> than 2-5%. I remember bumping a 386 16 to 20Mhz
> with no problems. It would
> almost run reliably at 24Mhz and I've done a lot of
> similar overclocks.
> Years ago I doubled the speed of a Trash 80 Model
> 100 (I had to replace the
> processor and the 600ns ROM but nothing else) and
> had an engineer on a
> support forum for the machine kindly explain that
> what I had done was
> impossible because of various component specs. I
> guess they thought I was
> lying but I offered to have them see for themselves
> since some of them lived
> within a reasonable drive but no one took me up on
> it. This 'impossible'
> machine ran happily for many moons until it was
> retired to my 'museum',
> though I still pull it out once in a while just to
> play with it. I think
> you could probably just swap out the crystal in the
> Newt but you WOULD lose
> the serial functionality (and ethernet and possibly
> modem, depending on the
> devices used) and have squeeky sound. That's what's
> cool about the Pix
> upgrade.
>
> Jon.
>
> -----Original Message-----
> From: Ed Kummel [mailto:tech_ed@yahoo.com]
> Sent: Saturday, April 01, 2000 12:32 AM
> To: newtontalk@planetnewton.com
> Subject: Re: NTLK Re : The Newton's Sucessor
>
>
> I don't think that you can...I mean I don't think
> that
> you could just "pop" in a crystal and go...the
> reason
> is in the way that the Newt uses it's memory. If you
> clock the Newt to a higher speed, you will reach a
> threshold where the Newt will fail due to memory
> timing anomolies...and that threshold will be quite
> small, probably no greater than a 2-5% speed
> increase.
> Not worth it. What makes the Impact 2000 upgrade
> work
> is that it has buffer chips which aid in the memory
> timing problems that you would run into. Also it
> seems
> that the serial port is clocked to processor xtal
> frequency, meaning that if you clock your Newt, you
> will no longer be able to use your port for
> connecting
> to your desktop machine. The Impact 2000 solves this
> by having a second xtal on board that falls back to
> the original speed in order to maintain
> compatibility.
> ed
> web/gadget guru
>
> --- ZACINCCEO@aol.com wrote:
> > How can I overclock my newton?
> > -Zac
> >
> >
> >
> <snip>
>
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