and Warnings before
you start !
The platform is static
sensitive - you should make sure that your workplace has a conductive
surface that is properly grounded to avoid static voltage build-up.
Static discharge while touching components will positively
destroy the board.
You need at least a good fine
potential-free electronic solder iron. Or in the worst case a
gas-powered solderer to do the most of the modifications described
here. And at least average solder skills.
However: None of the modifications that require soldering operations
are of very high complexity or over-average difficulty range (Except
where otherwise noted).
You will need quiet hands nontheless.
Rethink again about the value
of the platform. If you are in doubt that your skills will suffice and
are a bit worried remembering how much care and money it may cost to
get another P-90 platform ... leave it.
Or try to get someone else to do it.
The reworks are not very difficult but before you ruin a good working
platform: Think. And think again.
The modifications are mainly easy reversible for the sake of the
The usual disclaimer: You are
doing it on your own risk. The maintainer is not responsible for any
damages or losses, neither as direct or indirect consequence.
Or in simple words: if you louse it up - it's your problem !
A few serious words on
The last BIOS for the Type-4
platform was Revision 10. It was designed
to solve some problems for machines running OS/2. The Revision 09 never
really made it into the public, since it contained some serious bugs
and was pretty soon superseeded by the 10 version. This however has
some downsides with faster processors. It works fine with e.g. a 120
MHz clocked CPU (a P-133 set to 1:2 bus / core ratio at 60 MHz base
clock) but faster
combinations often end up in a 0129 xxxx error. I don't know exactly
what BIOS change caused this misbehaviour, but it is a known fact.
Obviously the Revision 10 alters some settings for the cache controller
that are not really well thought out.
Therefore I would suggest to stay
with the BIOS revision 08, which had
prooved to run reliably with the Pentium Overdrive 200 (PODP200) as
well as with a souped-up platform with the "Classical Pentium" 200 or
even a MMX interposer and - at least - a Pentium MMX running at 180 MHz
with the unmodified 60 MHz base clock.
233 MHz with a modified 66 MHz
base clock is difficult. Most likely the
board has too little time to synchronize between cache memory and
processor core and accomplishes severe mis-hits and the system crashes
with cache errors / processorboard errors of the 0129 xxxx family.
While BIOS updates are a
sensible and vital operation I would recommend
to upgrade / downgrade the platform BIOS before any processor
or clock rate changes. Particularly altering the clock from 60 to 66
MHz might be quite hard
to digest for the board and it may - or may not - fail to properly get
the new BIOS version installed.
If it fails there is a good
chance to render the platform non-functional !
There are no known ways to re-install a working BIOS flash from outside
or restore the old version or do a "desaster recovery" as known from
modern boards. The platforms' BIOS chips are soldered and cannot be
removed for reprogramming in an Eprommer.
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