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Table of Contents
[-0-] Version History
[-1-] Precautions and Warnings before you start
[-2-] Introduction to the Type 4 "Y" Pentium 90 Platform
[-3-] The importance of cooling certain components
[-4-] Modification A) Using a Pentium Overdrive 180 / 200
[-5-] Modification B) Hardwiring the BF0 / BF1 Pins for different Bus / Core ratios
[-6-] Modification C) Changing the Base Clock from 60 to 66 MHz
[-7-] Modification D) Using a Pentium MMX 233 MHz with an Interposer
[-8-] Problems, Workarounds and other stuff
Content by Peter H. Wendt (original HERE). Edited by Major Tom.
Precautions and Warnings before you start
The complex is sensitive to electrostatic discharge (ESD). You should
make sure that your workplace has a conductive or static dissipative surface
that is properly grounded to avoid build-up of static charge. If you don't have
appropriate working surface, at least discharge yourself by touching some
grounded metal object. Try to do this regularly when working on the board
(before you touch it!). Static discharge may destroy or degrade the ESD
sensitive ICs and/or other components. You will need a soldering iron with a fine tip, and ideally with some
kind of temperature control. None of the modifications that require soldering
operations are of high complexity or over-average difficulty range (Except
where otherwise noted). But you will need some basic soldering skills and
steady hands. Think again about the value and rarity of the "Y" complex. If you don't
feel confident about your skills and are a bit worried remembering how much
care and money it may cost to get another "Y" board... just don't risk it. Be
happy with what you have or try to get somebody more experienced to do the work
for you.
Most of the modifications are easily reversible, for the sake of
all the purists out there. As always, the information presented here is provided with no warranty.
If you decide to realize any of the modifications described here you are doing
so at your own risk! The authors can't be held responsible for any damages or
losses arising from use of this information.
A few words about the platform BIOS
The last official BIOS for the Type 4 platform is Revision 10. There has
been speculation that this revision is more problematic than the earlier
Revision 08 when used with processors running at 200 MHz or higher. However,
this has never been confirmed.
A comparison of the disassembly for Revisions 08, 09, and 10 revealed that
the later revisions do not contain any code changes that could affect the
platform stability. All processor complex registers are configured the same
way, and there are no timing-related modifications (apart from an unrelated
keyboard initialization delay).
More information about the different BIOS revisions can be found
HERE.
Achieving stable 233 MHz operation with a modified 66 MHz base clock can be
challenging and may lead to random crashes or POST errors in the 0129 xxxx
range.
Important: Updating the BIOS is a sensitive and
potentially risky process, so it's best to upgrade or downgrade the platform
BIOS before making any changes to the processor or clock rate. In particular,
changing the clock from 60 MHz to 66 MHz can be challenging for the board and
may cause instability. The last thing you want is a system crash during the
flash update process.
In rare cases, a failed flash update may render the
complex non-functional. Normally, this shouldn't happen because each
flash chip is updated individually, ensuring at least one functional copy of
the Stage 1 POST code is always available. However, if the update process is
interrupted, you might need to move the bank selection jumper to its other
position, allowing the system to boot into a flash-recovery mode (more
information HERE).
However, if that doesn't work for some reason, there is no other easy way to
recover the BIOS. The flash chips are soldered in place and can't be removed
for reflashing with a programmer - at least not without a rework station.
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