Here follows a brief summary of PCI chipsets. I've tried to keep it
accurate, but if you spot any flaws please feel free to cor […]
Here follows a brief summary of PCI chipsets. I've tried to keep it
accurate, but if you spot any flaws please feel free to correct me, and
if you have details on other chipsets, please feel free to let me know
about them. 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). Where I know for sure that they do, I have indicated
that a chipset will use parity RAM. PCI Vendor IDs first in HEX then in
decimal appear in brackets beside the chipset names.
Usefull numbers: (8/27/95)
ALI: (408) 764-0644 (sales)
Intel: (800) 628-8686 (tech. support)
PART ONE: 80486 Chipsets
1) The Aries Chipset (Intel: 8086/32902) (8/28/95)
This is a chipset made by Intel for 80486-based machines, and used in
boards (such as the Asus AVP4) where PCI and VL buses are to coexist.
Unlike the Contaq chipset below, the Aries chipset implements PCI using
a PCI to CPU bridge, and the VL bus is attached to this. This allows
for full PCI performance, though I don't know what effect it has on VL
(which likely will run no faster than the 33 MHz at which PCI 2.0 runs).
The chipset has apparently been through at least two revisions, at least
one of which has problems with protected-mode code and zero wait-state
cache operation. (This may be worked around via the system BIOS by
setting the cache so that it uses 1 wait state for its operations.) In
addition, this chipset does not support PCI - PCI bridges, as the
Adaptec 3940 does not work with it.
2) The Contaq Chipset (Contaq: 1080/4224) (8/27/95)
The Contaq 82C599 is paired with one of their 486VL chipsets (82C596 or
82C597) and bridges directly from the 486 CPU to the PCI bus.
Paraphrased from the Contaq spec.:
The 82C596 system controller provides the CPU interface, VESA bus
interface, ISA bus controller, etc. The 82C599 PCI controller provides
the bridge between PCI master/slave agent and the ISA/VESA standard
expansion bus; it arbitrates all the bus transactions between host CPU,
PCI agent, VESA device, and ISA device.
(Which sounds to me like the PCI bus is attached to the VL bus, rather
than to the CPU, which will cause PCI performance degredation.)
3) The FINALI-486 Chipset (Acer Labs: 10B9/4281) (8/27/95)
This is ALI's chipset for 486 systems, consisting of the M1487 and M1489
chips. It supports EDO RAM and all the different 486 CPUs, and has IDE,
a real-time clock, and a keyboard controller. I've no reports of
success with boards using this chipset, and ACER 486's which use the
board usually have slow cache controllers. Use CTCM to check your
4) The Opti Chipset (Opti: 1045/4165) (8/27/95)
Components: 82C822 (PCI functions)
82C895 (all other functions)
This is Opti's chipset for 486-based machines. It's reported to work
well with OS/2, although it implements PCI using a VL-to-PCI bridge
instead of the other way around. Apparently this chipset will only
allow 1 32-bit burst transfer per bus arbitration cycle, which limits
throughput to 8 MB/s instead of (the maximum ideal transfer rate of) 132
MB/s. Boards which use this chipset are, therefore, to be avoided.
5) The Saturn Family of Chipsets (Intel: 8086/32902) (8/27/95)
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 VL 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.
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. This chipset, when
presented with a device which transfers 100 Mb/s, doesn't seem
to let the CPU run at all.
6) The SIS chipset (Silicon Integrated Systems: 1039/4153) (9/4/95)
Components: 85C496 and 85C497
SIS makes a separate chipset for 486-based boards which is commonly used
in systems which also have VL slots. Unfortunately, it sounds as though
the chipset implements PCI by bridging it to VL (instead of the other
way around), so PCI-based systems which have VL slots will suffer a
degredation of PCI performance. Still, however, boards manufactured by
AMI and Asus have been reported to work well with OS/2. There have been
five revisions of this chipset. A4 (the earliest one) supports IDE up
to mode 2 but apparently was not stable with caches on. B2 had
on-board IDE support but did not support mode 3 well. Revisions B3 and
later apparently work better. The varisous chipset revisions can be
identified by their labels:
A4 Version chipset: SIS 496 MU, SIS 497 MW
B2 Version chipset: SIS 496 NU, SIS 497 NS
B3 Version chipset: SIS 496 NV, SIS 497 NS
B4 Version chipset: SIS 496 NV, SIS 497 NU
B4 Version chipset: SIS 496 OR, SIS 497 OT
None of these chipsets support PCI - PCI bridges, so that the Adaptec
3940 will not work with any motherboards which use this chipset.
7) The VIA GMC chipset (Vendor unknown) (8/27/95)
This chipset includes the VIA VT82C486A-F with a built-in 8042 keyboard
controller and a VIA VT82C505-D chipset for the VESA to PCI bridge.
Specifically, the chips are as follows:
82C486A - cache/memory controller + VLB to ISA bridge
82C482 - VLB to ISA bridga (why there are two I'm not sure)
82C483 - DRAM controller
VT82C505 PCI to VLB bridge
A board using this chipset has been unstable (even under DOS/Win), and
did not work with an Adaptec 2940 SCSI controller under OS/2 at all.
Boards based on this chipset are therefore to be avoided. I have,
however, had one report of success from someone using revision G of this
chipset, so it could be that the new revision fixes problems with older
rev's. Designers with whom I've corresponded indicate that improperly
designed boards which use this chipset may have unstable caches. In
addition, the cache controller reads the data into the cache SRAMs
first, then into the CPU, increasing latency and reducing throughput.