Check 64 bit DMA from Disk-Controller (amd64/135040)

[Ralf Folkerts]

Hi,

I asked this a while ago but didn't get a reply - as, however, no one 
replied that such a check is impossible I'd like to ask again:

My SB600 ATA-Controller used to cause massive Problems (from disk not 
being detected at all to disk being detected but later "trashed" during 
buildworld) with DMA with 4G RAM. I circumvented that by setting 
"hw.physmem=4g", as recommended by John Baldwin.

Now I'd like to perform a test, if this DMA-issue was *really* fixed by 
a recent BIOS-Update.

How can such a test being performed? Or is it impossible at all?

I already ran several buildworld/buildkernel instalworld/installkernel 
to a "fresh" disk in a row after the BIOS-Update - and didn't see any 
Problems - unlike previously where the disk was at latest trashed during 
the first run.

However, I have no idea whether these runs were successful because of 
the DMA issue being fixed or simply because by some coincidence no DMA 
was being performed beyond 32 bit addressability.

Would really be cool to get some confidence - as I'd like to run ZFS but 
don't think it'll be much fun with the hw.physmem being set to 4g :-(

Many thanks in advance!

Btw: System is now "8.1-STABLE FreeBSD 8.1-STABLE #0: Fri Nov 12 
19:45:42 CET 2010 amd64"

I ran my Tests against the 8.1 RELEASE (booted off USB Stick, then 
installed to a "fresh" disk.

Cheers,
_ralf_