THE SITUATION The Type-4 P90 complex (as used on the Server 500 machines) is currently the hot ticket in PS/2 performance upgrades. Several different types of modifications have been reported on the newsgroup as being successful, including the one detailed here. This specific modification was done by myself on one of my complexes. Note that although I've got a stable, solid performing machine at this point I did experience various *quirks* in the past. I believe that the *quirks* have been resolved by adding cooling to the transistor on the Evergreen CPU adapter.

THE SOLUTION Modifying the P90 complex to run a P233-MMX requires two major steps, the first of which isn't really for the faint of heart since it requires that the 60MHz oscillator on the precious P90 complex be desoldered and replaced with a 66MHz unit. I must admit that I shed some sweat the first time I did this, but rest assured that it's not *all* that difficult to do if you have the appropriate tools and a steady hand. A suitable replacement oscillator part is the Epson SG-615PH at 66.6667MHz, which can be bought from vendors such as Digikey. Also, if you have an old Model 77 planar to waste you can donate its heart (the 66MHz IBM-branded oscillator) to your complex as well. Here's how a stock P90 card looks without the heatsink: Between the processor and the cache controller is the oscillator, which gets replaced by a faster 66.667MHz unit: (Note: I've used the 66MHz, 66.667MHz, and 66.6667MHz oscillators successfully) Once the oscillator is replaced, the complex operates at 66MHz, much like the Type-4 P66 complex. The second thing necessary to accomodate a P233-MMX CPU is (in my case) this Evergreen CPU adapter. It takes care of both the voltage-conversion and clock-multiplying duties. Here's how the top and bottom of the Evergreen adapter looks: Here's how it looks with the Pentium 233MMX CPU on it: The jumper settings have been excellently documented on Louis' site. Here's a full view of the completed P233 -MMX Type-4 complex (without heatsinks mounted): Here's a close look at the fully mounted Evergreen unit: (note that I attached the heatsink from the transistor on the Evergreen adapter to the CPU's heatsink) Well, this is probably about as fast as you can go in a single-processor Micro Channel machine (for now). Your mileage may vary, of course. I'm still experimenting with some other stuff, but so far an attempt to run the AMD-K6 hasn't panned out. Disclaimer: As with all other contents on this site describing modifications that may boost the performance of your hardware, the author(s) are only describing methods that are for the most part "experimental" in nature. Some of these modifications will void your manufacturers' warrantee, and at worst may also permanently damage your hardware. If you choose to perform any of these modifications, please do so understanding these risks, as the author(s) cannot be held liable for any loss or damage that may result.