[update] 8GB issues, Tyan 2885 K8W

[Jonathan Dama]

Several times in the past people have mentioned issues with
8GB of RAM on the Tyan 2885 K8W (including myself).

Tyan recently posted a BIOS update (version 2.04) which
corrects some issues in earlier BIOSs improperly computing
memory timings.

To summarize, I had experienced two issues:
1) I had observed panics under minimal load with 8GB with the 
   BIOS autoconfiguring the memory speed.  These problems were 
   correctable by manually degrading the RAM speed as was
   possible with the 2.02 BIOS.  Interestingly, memtest86+
   did not report issues with the autoconfigured settings.
   But this perhaps is not surprising because evidence is
   that timings were marginal--some sticks of memory would
   work others wouldn't.  e.g., I'd see situations were  CPU0 
   seems to handle the 4 stick load but not CPU1.  This of
   course is sensible due to component variation in a
   marginal configuration.  The 2.04 BIOS now properly
   automatically configures to stable memory settings.

   *Note the route of this is that you can get to 8GB using
   4 double-stacked DIMMs per CPU.  We got into a very 
   confusing situation because both single (double density) 
   and double-stacked DIMMs had been purchased and our techs
   weren't communicating or paying attention to that in
   their problem reports.

2) The second problem involves the onboard broadcom and
   silicon images chipset.  This problem has only manifested
   itself under heavy combinations of network and disk
   access.  Unfortunately, I've never gotten a good
   crash-dump and the problem is hard to reproduce.
   I do not see similar issues with the em, ahc drivers.
   Nor did I see similar issues with the broadcom and si
   hardware under linux

I hope this commentary is useful to people.  I apologize for
not having anything definite to report on #2.  But the take
away is that nothing is intrinsically wrong with FreeBSD
5-Stable on Tyan K8W (S2885) with 8GB--though something
might be lurking in the onboard peripherals.

-Jon