386 UNIX DMA

[John Unekis]

     Perhaps some knowledgeable soul out there could help us with a rather
     vexing problem. We are trying to add devices to a workstation computer
     using the intel 386 processor and the ISC UNIX operating system (386/ix). 
     Twice now we have purchased Beta-test versions of device drivers which
     would not work on our system. In both cases the devices being driven 
     exchanged data and control info through PIO addresses instead of memory
     addresses. In both cases the drivers attempt to do DMA transfers to the 
     PIO addresses and can not accomplish this. In both cases the drivers
     seem to work if the I/O is done using byte-at-a-time OUT's instead of
     DMA, but the throughput is 1/10 the DMA rate and is unacceptable. Also,
     in both cases the drivers were developed on AT&T 386 machines.

     In both cases the companies involved claim that the drivers work 
     'just fine' on their AT&T machines. We have tried them on two 386 boards,
     the Sigma Designs and the Texas Microsystems with no success.

     Does anyone out there know anything about the DMA on the AT&T boards?
     Is it somehow non-standard? Are the other two 386 boards non-standard?
     Has anyone else had a problem with drivers developed on an AT&T machine
     not working on other processors? Was it resolved?

     Any help is appreciated.

     {ihnp4 or voder or jplgodo}!wlbr!etn-rad!jru