Date: Wed, 23 Aug 1995 00:06:48 -0700 From: "Jordan K. Hubbard" <jkh@time.cdrom.com> To: doc@freebsd.org Subject: From a recent posting of Rod's: Message-ID: <3530.809161608@time.cdrom.com>
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Saturn-I may have some problems here, don't know, don't have access to
a Saturn-I based machine. Saturn-II seems to handle 4 bus masters
without any problem, and I suspect a Saturn-II can run the Meteor just
fine. But then, doing video capture on a 486 class machine does not
make a whole lot of since given the CPU demand needed to do mpeg.
[Note: What follows would make a great table in a hardware FAQ! Are
we actually doing this now? Anyone care to kick it off? I'm too
busy myself with 2.1 right now to inaugerate such a thing, but I'd
be happy to contribute bits and pieces -jkh ]
Of the Intel PCI chip sets the following is a list of brokenness from
worst to best and a short description of brokenness.
a) Mercury - Cache coherency problems, especially if there are ISA
bus masters behind the ISA to PCI bridge chip. Hardware flaw, only
known work around is to turn the cache off.
b) Saturn-I (ie, 82424ZX at rev 0, 1 or 2) - write back cache coherency
problems. Hardware flaw, only known work around is to set the external
cache to write-through mode. Upgrade to Saturn-II.
c) Saturn-II (ie 82424ZX at rev 3 or 4) - works fine, but many MB manufactures
leave out the external dirty bit SRAM needed for write back operation.
Work arounds are either run it in write through mode, or get the dirty
bit SRAM installed. (I have these for the ASUS PCI/I-486SP3G rev 1.6
and later boards).
d) Neptune - Can not run more than 2 bus master devices. Admitted Intel
design flaw. Workarounds include don't run more than 2 bus masters,
special hardware design to replace the PCI bus arbiter (appears on
Intel Altair board and several other Intel server group MB's). And
of course Intel's official answer, move to the Triton chip set, we
``fixed it there''.
e) Triton - No known cache coherency or bus master problems, chip set does
not implement parity checking. Workaround for parity issue - wait for
Triton-II :-(.
f) Triton-II - Unknown, not yet shipping :-(.
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