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Cutting a long story short, I stuck 2 peltiers either side of the StrongARM chip (front/back of PCB) with two 'ThermoEngine' cpu coolers on top of those.
I also changed the 3.6MHz crystal on the SA board for a 4.91MHz one to get above 287MHz.
After completley sealing around the CPU and sealing the board from free air (to stop condensation) I tested the setup, you can see the results below.
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Here is the output from !SICK with the overclocked StrongARM.
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| Guesswork |
'-----------'
Computer model: Acorn RiscPC SA
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| Processor |
'-----------'
Type: SA110, rev. J or K
Architecture version: ARMv4
Implementor: Digital
Clock rate: 304.8 MHz
The Bogomips port on the RISC OS Unix ports page reports 201.8 BogoMIPS.
A 233MHz Strongarm is 154 BogoMIPS.
A 202MHz Strongarm is 131 BogoMIPS.
Not bad for a 200MHz chip. :-)
Note from 'Bogomips': Bogomips is a standalone program that displays your system performance using one of the world's most recognized benchmarks. It uses the same code that is used in the Linux kernel while booting, but runs as a user program.
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The As you can see from the image on the right (click to enlarge) I had to modify the bottom slice slightly to accommodate the extra heatsource within the case. I installed a set of 3 fans at the front (Available from Maplin/PCWorld), and some fans just to the left of the podule bay which will also prove useful for keeping air flowing over things like the ViewFinder when I get one.
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The RiscPC almost boots at ~325MHz, however the chip itself doesn't get sufficiently cool make the machine stable for a full boot.
Was it worth it?
Well, yes and no. It certainly satisfied my curiosity (and made me wonder about cooling with freon) as well as making the card over 100MHz faster. However it was not worth it from the standpoint of hassle and mess made when sealing the card with silicon rubber.
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Will you be selling this as a kit?
Definitely not, and I advise against doing anything as stupid as this.
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End.
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