On September 29, you wrote:
> > The problem is something with the LANCE addressing of memory.  The
> > LANCE chip can only address 16MB of memory, and by some unknown
> > reason it works good when there are less than 16MB in the machine.
> 
> This sounds suspicious.  16M is 22 bits.  Aren't Q-bus addresses 22
> bits wide?  Perhaps the lance driver is setting up the qbus mapping
> registers wrong or something, such that the physical address of the DMA
> buffer is mistakenly getting used as the Q-bus address of the buffer?
> Something like that could cause this sort of symptom.

  4M is 22 bits, not 16M....a Qbus machine can address at most 4M.

  If the Lance is having trouble with addresses above 16M, perhaps it
needs some sort of bounce-buffering.


                       -Dave McGuire
                        mcguire@neurotica.com