From: garvin@cfd.mae.ncsu.edu (Michael Garvin)
Subject: More Exabyte 8500c (and SCSI) questions/woes
Organization: North Carolina State University
Date: Thu, 19 Nov 1992 20:18:53 GMT

	I've also taken receipt of an Exabyte 8500c (compression) 8mm tape
drive, and it's giving me pains.  Following the instructions in Dave Olson's
posting of 17 Nov 92 (thanks for the info!) I reconfigured my kernel, altering
the tpsc config file to read:

        /* Entry for Exabyte 8500c - Michael Garvin, 11/19/92.  Copied entry
         * from 8500, changed "EXB-8500" to "EXB8500c", "{0x0, 0x14, 0x0, 0x0}"
         * to "{0x0, 0x14, 0x8c, 0x0}".
         * There are 3 densities, 8500 mode, 8200 mode, and 8500 mode with
         * compression, in order.
         */
        { EXABYTE8500, TP8MM, 7, 8, "EXABYTE", "EXB8500c", 6,
                "\40\4\16\0\200\7", {0x0, 0x14, 0x8c, 0x0},
          MTCAN_BSF|MTCAN_BSR|MTCAN_PREV|MTCAN_CHKRDY|MTCAN_VAR|MTCAN_SETSZ|
            MTCAN_SILI|MTCAN_CHTYPEANY|MTCAN_SETDEN|MTCAN_SPEOD|MTCAN_SYNC|
                MTCAN_SEEK,
          80, 4*60, 25*60, 5*60, 1024, 128*1024},

I installed the drive on controller 0, ID 7, and rebooted the new kernel.  I
then made the following devices:

	crw-r--r--   1 root     sys       23,241 Nov 19 14:13 nrtape
	crw-r--r--   1 root     sys       23,243 Nov 19 14:13 nrtapens
	crw-r--r--   1 root     sys       23,240 Nov 19 14:13 tape
	crw-r--r--   1 root     sys       23,242 Nov 19 14:30 tapens

The minor numbers were upped 16 from the default 224-227 to match the 8500c
(0x8c in the tpsc config file) entry.  I then tried tarring to the drive, which
died with the following error:

	tar: tape write error: I/O error

and produced the following console output (note the tape drive hiccuped first):

	WARNING: dma_map: address not word aligned
	sc0,7,0: cmd=0xA disconnected on non-word boundary (addr=C02185A9,
		0x0 left).  Resetting SCSI bus
	dks0d1s6: retrying request
	dks0d2s6: retrying request

Our setup is a Power Series 4D/440.  SCSI controller 0 has an internal 1.6 gig
system disk (ID 1), an Iris File on the rear external connector with four 2 gig
drives (IDs 2, 3, 4, and 5), an internal CD-ROM (ID 6), and the 8500c mounted
internally (ID 7).  We've also got a Jaguar differential SCSI controller with
four drives on each channel.

	My questions are: am I going too far with that SCSI chain?  I have a
sinking feeling that I'm pushing the length limit, giving me the error I saw
(although the 8500c failing might give me that).  Are my entries for the 8500c
in the tpsc config file correct?  Have I correctly made the devices (in
particular, did I get the minor number correct and do they correspond to the
8500c in compression mode)?  And finally, would someone have the correct density
to feed to BSD dump for this drive (I calculated something around 47.5 million,
which sounds wrong).  Thanks for any help, I'm banging my head at this point.

-- 
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Michael Garvin - Systems Programmer			garvin@mmrc.ncsu.edu
Mars Mission Research Center				(919) 515-5250 [Voice]
North Carolina State University				(919) 515-7968 [FAX]
Newsgroups: comp.sys.sgi