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PCI_CHIP
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1994-11-07
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Hi All,
Here follows a brief summary of PCI chipsets, last revised Nov. 7/94.
I've tried to keep it accurate, but if you spot any flaws please feel
free to correct me. I've now added information on what is reported to be
another good chipset, made by Contaq for use with 486 CPUs and their VL
chipset. Anyone with details on others please feel free to let me have
'em. I've included information at the end of this list to help people
ID the chipset (assuming they have an Intel chipset on their
motherboards).
1) The Contaq Chipset
------------------
The Contaq 82C599 is a good 486 chipset, it's paired with one of their
excellent 486VL chipsets (82C596 or 82C597) and bridges directly from
the 486 bus to PCI. This is as distinct from the Opti VL/PCI
combinations, which bridge from VL to PCI, which causes a real
performance hit (especially with Pentiums). This could be the 'Aries'
chipset which the Asus VL/PCI 486 board uses.
2) The Saturn Family of Chipsets
-----------------------------
The Saturn family of chipsets is designed for use exclusively with 80486
and compatible processors, up to DX4s. They will, as of the latest
revision, work with the P24T Pentium Overdrive processor. Boards which
use them typically are of the combination ISA/PCI type, as I do not
believe the Saturn chipsets were designed to handle local bus
extensions.
The Saturn chipset has been through three revisions, numbered (oddly
enough) 1, 2, and 4. Some brief comments on each:
Rev. 1: Is now long-since discontinued. This chipset will only appear
on older motherboards (perhaps pre Jan. '94?), and should not
be on any motherboards of recent vintage. This chipset had
problems (unknown to me), and so was put through its first
revision and re-released.
Rev. 2: Is still in wide use. This chipset has problems with cache
integrity during PCI to CPU burst mode operations, as well as
certain SCSI operations. Any board which uses this chipset
today will still have these problems. There are BIOS "fixes"
provided by various manufacturers, but what these usually do is
disable the high-performance options on the chipset. Rev. 2
was never 'fixed', and there is no such thing as a newer
release called rev. 2. Because of the bugs, however, a new
version of the Saturn chipset was released relatively recently.
Rev. 4: With this release of the Saturn chipset, Intel seems to have
finally fixed the problems with the earlier revisions. This
chipset (also called Saturn II) also supports all the green
features when used in combination with the right BIOS. It is
distinguished externally from its older cousins by the last two
letters on one of the three chips. Check for a 'ZX' to
positively identify the Saturn II chipset. If you want a
motherboard with an Intel chipset, this is the chipset to use
with OS/2.
3) The Mercury Chipset
-------------------
The Mercury chipset is designed for use exclusively with 60 and 66 MHz
Pentium processors (so you won't see 486 motherboards with it, or 90/99
MHz boards with it either). It has, apparently, been through two
revisions as well, though I'm not aware of problems with the first rev.
More than likely the second rev. was just to add support for green
features.
4) The Neptune Chipset
-------------------
The Neptune chipset is designed for use exclusively with 90 and 99 MHz
Pentium processors (so you won't see 486 motherboards with it, or 60/66
MHz boards with it either). The Neptune chipset has been through two
revisions.
Rev. 1: This chipset was in boards shipped by Intel to vendors up until
about the end of July 1994. It has/had problems with posted
buffered writes, which would manifest themselves most
prominently with SCSI devices (which used this feature
extensively). Recent releases of the AMI flash BIOS which
Intel ships with their boards (the latest is 1.00.10.AX1)
switch posted buffered writes off on the chipset when rev. 1
of the chipset is detected.
Rev. 2: This chipset is in boards shipped by Intel to vendors as of
about mid August 1994. It has no reported problems (and works
well in my system).
Useful Information:
-------------------
How to find out your motherboard PCI chipset revision:
(Requires DOS support to be installed.)
THE FOLLOWING INFORMATION IS SUPPLIED WITHOUT ANY WARRANTY, EITHER
EXPRESS OR IMPLIED, OF ANY KIND. UNDER NO CIRCUMSTANCES MAY I (PATRICK
DUFFY) BE HELD LIABLE FOR ANY DAMAGE RESULTING FROM USE OF THE
INFORMATION GIVEN BELOW. YOU (THE READER) ASSUME FULL RESPONSIBILITY
FOR ITS USE AND THE CONSEQUENCES THEREOF.
The following commands will identify various aspects of your motherboard
PCI chipset. Type each command as it appears (and press enter, of
course). I've tested this on my own motherboard and it seems to work.
Under the result column, '-' means that nothing will be shown. I do not
know what the result codes will be for the Contaq chipset, so please
feel free to let me know.
Command Result Comments
debug Enter debug.
O CF8 F0 - Open PCI interface.
I C000 86 Chipset manufacturer ID: `8086' means
I C001 80 Intel, any other value implies the other
bytes are nonsignificant.
I C002 DeviceID_LSB
I C003 DeviceID_MSB Chipset's ID
I C008 RevisionID Revision number
O CF8 00 - Close PCI interface
quit Exit debug.
The chipset's ID can be 0483 (Saturn) or 04A3 (Mercury/Neptune)
For the Saturn chipset, revision 1/2 is for Saturn I, rev. 4 is Saturn II.
For Mercury/Neptune: revision 1/3 is for Mercury I/II, and revision
10/11 is for Neptune rev. 1/2.
So that's what I know, as clearly as I know how to say it. If you have
any questions or notice any ambiguities please do let me know and I'll
do my best to correct them.