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README file for the Linux DTC3180/3280 scsi driver.
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by Ray Van Tassle (rayvt@comm.mot.com) March 1996
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Based on the generic & core NCR5380 code by Drew Eckhard
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SCSI device driver for the DTC 3180/3280.
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Data Technology Corp---a division of Qume.
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The 3280 has a standard floppy interface.
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The 3180 does not. Otherwise, they are identical.
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The DTC3x80 does not support DMA but it does have Pseudo-DMA which is
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supported by the driver.
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It's DTC406 scsi chip is supposedly compatible with the NCR 53C400.
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It is memory mapped, uses an IRQ, but no dma or io-port. There is
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internal DMA, between SCSI bus and an on-chip 128-byte buffer. Double
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buffering is done automagically by the chip.
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Data is transferred between the on-chip buffer and CPU/RAM via
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memory moves.
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The driver detects the possible memory addresses (jumper selectable):
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CC00, DC00, C800, and D800
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The possible IRQ's (jumper selectable) are:
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IRQ 10, 11, 12, 15
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Parity is supported by the chip, but not by this driver.
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Information can be obtained from /proc/scsi/dtc3c80/N.
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Note on interrupts:
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The documentation says that it can be set to interrupt whenever the
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on-chip buffer needs CPU attention. I couldn't get this to work.
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So the driver polls for data-ready in the pseudo-DMA transfer routine.
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The interrupt support routines in the NCR3280.c core modules handle
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scsi disconnect/reconnect, and this (mostly) works.
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However.....
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I have tested it with 4 totally different hard drives (both SCSI-1
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and SCSI-2), and one CDROM drive.
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Interrupts works great for all but one specific hard drive. For this one,
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the driver will eventually hang in the transfer state.
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I have tested with: "dd bs=4k count=2k of=/dev/null if=/dev/sdb". It
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reads ok for a while, then hangs. After beating my head against this for a
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couple of weeks, getting nowhere, I give up.
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So.....This driver does NOT use interrupts, even if you have the card
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jumpered to an IRQ. Probably nobody will ever care.
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Nor will I when the $380 2.5GB IDE drives hit the market in early 1996!
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