"Overclocking" a //c+?

Michael J. Mahon

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Oct 11, 2001, 5:15:48 PM10/11/01

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I asked this question a few weeks ago, but didn't see any response...

Has anyone tried replacing the 16MHz oscillator in the //c+ to
run its accelerated mode faster? This should work, in principle,
but I wonder if anyone has tried it.

-michael

Email: mjm...@aol.com
Home page: http://members.aol.com/MJMahon/

Quadrajet1

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Oct 12, 2001, 12:07:40 AM10/12/01

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>
>I asked this question a few weeks ago, but didn't see any response...
>
>Has anyone tried replacing the 16MHz oscillator in the //c+ to
>run its accelerated mode faster? This should work, in principle,
>but I wonder if anyone has tried it.
>
>-michael

It's been a number of years since I've peeked into an //c+, but unless it
has a separate crystal for just the CPU, then no. If it has 1 crystal, then
all the other circuits in the system are dependent on that clock signal being
16 Mhz, for instance. So in principal it won't work at all.

On a machine like the Quadra 700, the CPU has it's own crystal, and so
swapping the 50 Mhz crytal for a 66 Mhz one (going from a CPU speed of 25 to
33) is not a problem.

Raymond

Michael J. Mahon

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Oct 12, 2001, 1:42:35 AM10/12/01

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Raymond replied:

> It's been a number of years since I've peeked into an //c+, but unless it
>has a separate crystal for just the CPU, then no. If it has 1 crystal, then
>all the other circuits in the system are dependent on that clock signal being
>16 Mhz, for instance. So in principal it won't work at all.
>
> On a machine like the Quadra 700, the CPU has it's own crystal, and so
>swapping the 50 Mhz crytal for a 66 Mhz one (going from a CPU speed of 25 to
>33) is not a problem.

The //c+ has a separate CPU crystal, since it is essentially a discrete
implementation of a Zip Chip--hence the question of overclocking. Clearly,
if the CPU speed were tightly coupled to system bus/video generation speed
any modification would be problematic, to say the least. ;-)

Wayne Stewart

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Oct 13, 2001, 1:19:43 AM10/13/01

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"Michael J. Mahon" wrote:

> I asked this question a few weeks ago, but didn't see any response...
>
> Has anyone tried replacing the 16MHz oscillator in the //c+ to
> run its accelerated mode faster? This should work, in principle,
> but I wonder if anyone has tried it.
>
> -michael

I've picked up a 20mhz oscillator to try but I'm planning to wait until
after our Apple II meeting on the 22nd. Don't feel like taking a risk
with the IIc+ before then since I'm planning on doing a small demo
comparing the IIc, IIc+ and Laser 128EX. Also thought we'd try
comparing the Apple LCD display with the C-VUE. Hope we'll at
least be able to see the text there.

Wayne

Obsbedia2

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Oct 17, 2001, 10:11:11 PM10/17/01

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<< since I'm planning on doing a small demo
comparing the IIc, IIc+ and Laser 128EX. Also thought we'd try
comparing the Apple LCD display with the C-VUE. Hope we'll at
least be able to see the text there.

Wayne>>

I can't make it to the meeting, Wayne :-), so how about some highlights?
Jay Edwards

Wayne Stewart

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Oct 19, 2001, 10:22:28 PM10/19/01

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Obsbedia2 wrote:

Wish you could make it. I'll let you know how it goes.

Wayne