garyj@neptun.pcs.com (Gary Jennejohn) (04/26/91)
I assume that Randy is working on a driver for the AIC6250. I'm also in the process of writing one. Since my attempts to mail Randy directly always get bounced I'll use the mail group to discuss it. I wrote my driver so that it uses the AUTOMATIC PIO (APIO) feature of the chip for transferring commands and messages (actually, at the moment ALL data transfers use the APIO, I haven't gotten around to using DMA yet). I did this because I didn't want to have to handle SCSI phase changes in the middle of transferring messages with DMA. APIO allows me to read/write a byte, check if the phase changed, and then continue accordingly. It's also much easier to implement APIO in a polled driver. Once I get interrupts going I'll probably switch to DMA for all transfers. Using APIO I have gotten the (polled) driver to the point where read/write works without problems. The only difficulties I have had come immediately after power on. The chip in my system always asserts ATN which causes my disk drive to go bonkers. I see the weirdest phase changes on the bus when I try to select the disk the first time. Once I've managed to do a select everything works fine. The strange thing is that Jordan Hubbard didn't see any of these weirdnesses when he tried out the driver. Must be something peculiar with my controller/drive combination. Randy, I'd be glad to exchange notes with you on this. As the Germans say, "geteiltes Leid ist halbes Leid" (shared misery is half misery). Gary