Introduction
to Type-4 Pentium 90 Platform
Location of the important components
The IBM Type 4 P-90 Platform is
also often referenced as the "Y-Platform" - because it showed up in the
few Mod. 9595-xYx machines. Originally it came with the Server 500 and
was offered as an option to the Model 95 series.
Preferably it is combined with the 95A planar, which can be identified
by the two serial and two parallel ports and which offers optimum
performance and support for all the platform features.
IBM Type 4 Platform with Pentium 90
The codename of the platform was
"Cubrun" (rumour says it were a small river), the IBM numbers
brought in connection with it are
P/N 06H8589, FRU 06H7095 (with flawless P90)
P/N 06H3729, FRU 06H3739 (with buggy P90)
The latter one is the original P/N for FCC
application. Earlier P/Ns may still have a buggy Pentium
90 processor installed. Intel had them replaced on demand.
No problem if you plan to replace that P90 against something else
anyway.
The Type-4 platforms have 128KB IBM SurePath Flash-ROM based BIOS and
offer a Synchro-Stream Mode for 40MB/s data transfer rates (up to
80MB/s in 64-bit burst transfers).
This platform is a so-called "Socket-5" board. The CPU connector is LIF
(Low Insertation Force) but not ZIF (Zero Insertation Force) like the
Socket 7. The socket layout is staggered in contrast to the older
Pentium P60 and 66 and the 486 Type-4 platforms.
It uses the Intel Pentium 90
processor on a 2:3 bus/core ratio with a
base clock of 60 MHz.
The Pentium-90 processor is accompanied by an Intel 82497-60 Cache
Controller and a set of 10 Intel 82492-60 Cache RAMs for a total of
256K Level-2 Cache, 5 chips on either side of the card.
If you are lucky and got one of the platforms used on the last series
of the IBM PS/2 Server 500, you may have 66 MHz rated cache RAMs and
82497 cache controller installed. However: the oscillator on these is
still a 60.0000 MHz type and the platform runs on a 60 MHz base clock
too.
Never
ever install an 82496 cache controller from a P60 or P66 platform !
Not even for testing. It may even
appear
to work - but surely not for
long. The controller used on the P60 platform is a 5V-only type, the
one on
the P90 platform is a "dual-plane" 3.3V / 5V chip. The P60 controller
will short the 3.3V supply against the 5V and destroy cache RAMs and
CPU.
The P90 platform also has one
on-card voltage regulator for some of the
other logic chips (LT1085, 3 Amps, set to 3.75V) and another voltage
regulator for the Pentium
90 processor, the cache controller and the cache RAMs (LT1084, 5 Amps,
set to 3.3V).
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