Gigabyte 6VXDC7 mobo (Via 694X chipset) SMP instability

I have a machine with a Gigabyte 6VXDC7 mobo (Via 694X chipset) with a
pair of 933MHz P3s and a couple of GB of RAM.  I run Debian Sarge's
stock -686-smp kernels (2.4 series or more recently 2.6.8).

With a "nosmp" boot option (or using uniprocessor kernels) the box is
rock solid.  But when I run in SMP mode it generates sporadic
  "APIC error on CPUx: 0y(0z)"
type messages, generally in pairs, every few minutes (or several per
minute with the 2.6.8 kernel without a "noapic" boot option).
Eventually the machine invariably locks up hard with no warning after an
uptime of on the order of a few minutes or a few days (depending on
kernel version, boot options, load and luck).  I've tried just about
every possible combination of BIOS settings and boot options, memchecked
the RAM, rearranged PCI cards and upgraded the PSU.  Nothing seems to
help; the only way to get complete stability seems to be "nosmp" or a
non-SMP kernel.

Googling around, there seem to be plenty of reports of similar behaviour
in 694X systems, but little in the way of definite solutions (with the
possible exception of someone who claimed to have fixed it by lowering a
voltage setting in their BIOS; my board's BIOS doesn't my give any
control of that unfortunately).

Anyway, my question is this: is this chipset simply broken at the
hardware level (and I should just resign myself to uniprocessing) or is
there is some cunning combination of boot options and/or kernel compile
flag gnosis which will let me SMP with confidence ?

Thanks for any advice
Tim