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.
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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