Hardware and Upgrading:

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CPU

At first, if you own a single CPU machine and want to install an additional one,
you'll need a voltage regulation module (VRM) .
Use this link to find out if your VRM supports a faster CPU.

This was hard to get, so if i find the bill, i'll put up the name of the vendor.
Then you need another processor with the same stepping as your old one.
This was difficult, too. You cannot buy this one from a shop, so try eBay and
recommend a program from INTEL's web site which tells you the stepping ( i will post the link)
or look during boot up sequence - some pc bioses show the stepping.

Now to the CPU and board requirements .

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RAM

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PCI
working PCI device list

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HD

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PROM

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OS

In order to install Windows 2000, it is necessary to upgrade the version of PROM (firmware) to the thing after 1.1004 beforehand.
It is necessary to install the Supplemental Software Kit (SSK) from SGI after installing Windows 2000.

Linux runs through a custom HAL which you have to point to from the firmware bootup config screen.
However, no hardware acceleration is performed under x-windows.
I heard about SGI presenting the 320 with a h/w accelerated x OpenGL demo, but the driver has not been released to the public. 
A very good page about this topic can be found at http://linux-visws.sourceforge.net/

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