README file for the Linux DTC3180/3280 scsi driver.
by Ray Van Tassle (rayvt@comm.mot.com)  March 1996
Based on the generic & core NCR5380 code by Drew Eckhard

SCSI device driver for the DTC 3180/3280.
Data Technology Corp---a division of Qume.

The 3280 has a standard floppy interface.
The 3180 does not.  Otherwise, they are identical.
The DTC3x80 does not support DMA but it does have Pseudo-DMA which is
supported by the driver.
It's DTC406 scsi chip is supposedly compatible with the NCR 53C400.
It is memory mapped, uses an IRQ, but no dma or io-port.  There is 
internal DMA, between SCSI bus and an on-chip 128-byte buffer.  Double
buffering is done automagically by the chip.
Data is transferred between the on-chip buffer and CPU/RAM via
memory moves.

The driver detects the possible memory addresses (jumper selectable):
	CC00, DC00, C800, and D800
The possible IRQ's (jumper selectable) are:
	IRQ 10, 11, 12, 15
Parity is supported by the chip, but not by this driver.
Information can be obtained from /proc/scsi/dtc3c80/N.

Note on interrupts:
The documentation says that it can be set to interrupt whenever the
on-chip buffer needs CPU attention.  I couldn't get this to work.
So the driver polls for data-ready in the pseudo-DMA transfer routine.
The interrupt support routines in the NCR3280.c core modules handle
scsi disconnect/reconnect, and this (mostly) works.
However.....
I have tested it with 4 totally different hard drives (both SCSI-1 
and SCSI-2), and one CDROM drive.
Interrupts works great for all but one specific hard drive.  For this one,
the driver will eventually hang in the transfer state.
I have tested with: "dd bs=4k count=2k of=/dev/null if=/dev/sdb".  It
reads ok for a while, then hangs.  After beating my head against this for a
couple of weeks, getting nowhere, I give up.
So.....This driver does NOT use interrupts, even if you have the card 
jumpered to an IRQ.  Probably nobody will ever care.
Nor will I when the $380 2.5GB IDE drives hit the market in early 1996!


