Date: Mon, 19 Nov 2001 10:47:36 -0700 From: "Justin T. Gibbs" <gibbs@scsiguy.com> To: "Jose M. Alcaide" <jose@we.lc.ehu.es> Cc: scsi@FreeBSD.ORG Subject: Re: weird problems with on-board Adaptec 7880 Message-ID: <200111191747.fAJHlaY86236@aslan.scsiguy.com> In-Reply-To: Your message of "Mon, 19 Nov 2001 18:13:18 %2B0100." <20011119181318.C337@v-ger.we.lc.ehu.es>
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>I have a system based on a three-year-old Iwill PIILS motherboard. This >mobo includes an AIC7880 controller, which supplies a Ultra Wide SCSI >channel. There are two SCSI connectors (68-pin wide and 50-pin narrow) on >the motherboard. > >A few days ago I transplanted the motherboard to another system and I >attached some devices to its SCSI channel. I inmediately got speed >negotiation problems, and I tried several bus arrangements to no avail. >This is *not* a cabling or termination problem; I suspect that it is a termination problem. More below. >Currently I have *only* one device attached: the external DLT 4000 unit >(fast narrow SCSI). There is a flat 50-way cable from the appropriate >connector on the motherboard to an external micro-SCSI connector; from >here to the DLT there is a single standard SCSI cable, and I attached an >active terminator to the DLT's free SCSI connector, of course. Everything >is correct. Ensure the DLT does not have a jumper or dip switch for internal termination. >I entered the SCSI-select utility of the onboard AIC7880 and tried all >kind of things. Surprisingly, sometimes I achieved the 10 MHz sync speed >after enforcing a limit of 5 MB/s (!) for the DLT target. Weird. Anyway, >it did not work at all. Even a simple "mt status" gets hung until I reset >the bus. > >I am suspecting of problems with the SEEPROM. Maybe the ahc(4) driver does >not understand correctly the settings it reads from the SEEPROM... I don't >know. I found a option called "AHC_DUMP_EEPROM"; I can turn it on if it >could be useful. It may be useful. >**NOTE:** the SCSI-select utility offers only two choices for bus >termination: "High ON/Low Auto" or "High OFF/Low OFF". If I attach devices >to both SCSI onboard connectors (wide and narrow), the "boot -v" messages >keep saying "Low byte termination enabled". Is that the expected behavior? Depends on the motherboard. Many of these systems actually control the termination via a MB BIOS control. The SCSI Select controls were never disabled when the SCSI BIOS was compiled. I believe that this may be the cause of your bus instability. -- Justin To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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