P233MMX Overclock on P90!

Editor's Note: I like this MUCH better, because it involves NO soldering (other than the optional oscillator upgrade)

From Terminaut- Tam Pham

Well, I've finally achieved success in the elusive arena of "overclocking" a MicroChannel machine. I'm currently testing the "upgrade" using CheckIt 3 on the Server 95 in batch mode, and everything seems in order thus far. Here are some preliminary information on how the mod was done.

I started with an IBM PC Server 95 with 256MB ECC RAM and a Pentium 90 processor complex (which I received from a VERY HELPFUL fellow MAD. sufferer). The first step performed was to simply plug in a P233MMX chip that was sitting on top of an Evergreen processor adapter unit. This worked without problems, running the complex at 210MHz. Some of you may remember from a while back that I ran my PC Server 720 at 233MHz. That was accomplished using this same Evergreen adapter.

Jumper Settings
CLK MUL
P55C, M2, K6 (DUAL VOLTAGE) 3.5 (1.5) 3
P54C, K5 (SINGLE VOLTAGE) 2.5 2
P1
OFF
OFF
ON
ON
P2
OFF
ON
ON
OFF
P3
OFF
OFF
OFF
OFF
CLK VCC P55C, M2, K6 6X86L SOCKET 5 (5V) P54C, K5, 6X86 SOCKET 7 (3.3V)
P4 ON OFF
CORE VCC
P54C, K5 6X86 3.3V
     K6       3.1V
P55C, M2 6X86L 2.8V
M2 2.5V
P5
ON
OFF
OFF
OFF
P6
OFF
ON
OFF
OFF
P7
OFF
OFF
ON
OFF
P8
OFF
OFF
OFF
ON

DIP switch settings to run a 233MMX chip:
 P1   OFF 
P2 OFF
P3 OFF
P4 ON
P5 OFF
P6 OFF
P7 ON
P8 OFF

With that configuration working, I proceeded to change out the 60MHz
clocking oscillator. This was done by carefully desoldering the stock unit
and replacing it with a 66.667MHz unit. I debated briefly on using the
66.667Mhz versus 66.0MHz oscillator (the P66 complex uses a straight-up
66MHz clock) and ended up with the 66.667MHz just for "aesthetic" reasons.

Well, that's about all it took. The system is now running at 233MHz and
seems happy about it. One thing I do want to do is replace the 60MHz cache controller chip with a 66MHz version. My prior P90 complex (the DOA one) had a 66MHz cache controller on it, but I sent that away.

I'm going to continue testing the system to make sure it is stable. If I see
any signs of trouble I'll update the newsgroup. Right now it's sitting with
the case open and running the CheckIt tests, but I'm going to get NT on
there as soon as possible. I've got a lot of things going on, but I'm
definitely going to try to take pictures tonight to post to a web page as
well.

Yippeeee!
 - I'm way past MAD