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[-1-]  Precautions and Warnings before you start !

[-2-]   Introduction to Type-4 Pentium 90 Platform

[-3-]   The importance of cooling certain components

[-4-]   Modification A) Using a Pentium Overdrive 180 / 200

[-5-]   Modification B) Hardwired BF0 / BF1 Pins for different Bus / Core ratio

[-6-]   Modification C) Altering the base-clock from 60 to 66MHz

[-7-]   Modification D) Using a MMX Interposer and P-233MMX CPU

[-8-]   Problems, Workarounds and other stuff

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Modification A) Using a Pentium Overdrive 180 / 200

The Pentium Overdrive 180 and 200 are somewhat hard-to-find items. They use the standard Socket-5 design with a single 3.3V DC power supply and use the offered 50, 60 or 66 MHz clock with internal clock-multiplying technology to run the core at much higher clock rates. The Pentium Overdrive 180 / 200 have integrated core voltage regulator and integrated clip-on cooling fan.

The Pentium Overdrive 180 had been designed to replace a Pentium 90, 120 or 150 Processor running at 3 x 60 MHz input clock with 180 MHz internally. The Pentium Overdrive 200 is basically the same 3 x clock multiplier - but intended to run 3 x 66 MHz to 200 MHz internally. It was intended to substitute a Pentium with 100, 133 or 166 MHz.

Nicely thought out ... but the P90 platform is not "Overdrive Ready".

Why ? Because the integrated cooling fan requires a +5V operating voltage to work. On the "Overdrive Ready" boards the two (normally unused) pins AN1 and AN3, which are marked "INC" (= Internally Not Connected) in the Intel datasheets for the Pentium P54C 75 - 200 MHz family, are connected with +5 VDC. On the P90 platform the two pins are not connected to anything - therefore the platform is not "Overdrive Ready" ....

But that is simple to achieve: you add one single wire connecting the two pins AN1 and AN3 with a +5VDC solder spot - like that marked edge of capacitor C179. And there you go. Nothing else required.

POD Modification

This modification is compatible with all other modifications explained in here.

If you think you could probably get a Pentium Overdrive 180 or 200 later, you could add this wire "just so" while you have the solder iron warmed up anyway right now.

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