data corruption with ahc driver and 4GB of memory using a FBSD-8 64-bit installation?

[Gary Jennejohn]

On Thu, 31 Jan 2008 12:42:05 -0700
Scott Long <scottl at samsco.org> wrote:

> Gary Jennejohn wrote:
> > Well, the thing which I find confusing is that the 32-bit installation
> > works without any problems.  I would expect the 64-bit installation to
> > work with 4GB, if anything does.
> > 
> > Does the 32-bit version use bounce buffers?
> > 
> > I'll try poking around some, but the 64-bit install is my (money earning)
> > work station and I can't afford to trash it, so I'm sort of unwilling to
> > risk it.  And I don't have any spare SCSI disks to use for testing.  Well,
> > I suppose I could sacrifice the 32-bit disk.  It's not so important.
> > 
> > Any hints on where to start looking?
> > 
> 
> Even with only 4GB of physical RAM, the motherboard will remap part of
> that RAM to be above the 4GB barrier.  So running in 64-bit mode with
> only 4GB of RAM will still exercise the >4GB bugs.  Let me think on
> where to point you for debugging...  The ahc cards don't normally use
> bounce buffers; they are designed to handle up to 2^39 bytes of RAM
> directly.
> 

Ah yes, I remember seeing something about the card using 39 bits for
addresses.  And you're correct, part of the memory was mapped from
0x100000000 to 0x11ffeffff.

I was thinking about getting the Adaptec 29320LPE, which is a PCIe
x1 card. Think that would have problems with 4GB? That would be the
ahd driver, I believe.

---
Gary Jennejohn