At 11:13 AM -0700 8/2/99, David Linker wrote:
>Additional information gleaned from disassembling my upgraded 230-2300 this
>weekend:
>
>There are two chips which I believe are the clock chips. One is labellled
>G3 and marked as follows:
>T 0512
> 31.3344
> 9525
>
>The other is labelled G2 and marked as follows:
>T 0568
> 22.5792
> 9528
>
>Note that the "T" is in a circle.
>
>I assume that these are the chips we would want to "clock chip", if we were
>to do that, and that the central numbers are the frequencies. I cannot
>figure out how they relate to the known clock frequencies.
The processor bus clock is supposed to be 33 MHz, and it's the one you want
to go after. There is probably another clock source somewhere which you
missed.
The 22.5 MHz clock is probably the source for the I/O bus, since the
developer note mentions it running at that speed. When I had a 1400
(similar motherboard architecture), I tried overclocking both the I/O bus
and the CPU bus. I was successful at overclocking the CPU bus to 40 MHz,
but raising the I/O bus to 33 MHz failed. The machine would boot and run,
but it would crash randomly.
BTW, I do remember also seeing a ~31 MHz clock in the 1400. The 1400 had
25 (I/O bus, slightly faster than the Duo), ~31 (?), and 33.33 MHz (CPU
bus) clocks.
The main thing to look at changing is the CPU bus to core multiplier ratio.
The normal speed is 100 MHz so the multiplier is set to 3x (3 x 33 MHz).
Setting it higher will increase the processor core clock without
overclocking anything else. This is set by several input pins on the 603e,
which are pulled to high or low logic levels on the motherboard.
Tim Seufert
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