Date: Mon, 28 Sep 1998 10:18:39 -0600 From: "Justin T. Gibbs" <gibbs@plutotech.com> To: Steve Passe <smp@csn.net> Cc: "Justin T. Gibbs" <gibbs@plutotech.com>, scsi@FreeBSD.ORG Subject: Re: p2b scsi termination Message-ID: <199809281625.KAA02664@pluto.plutotech.com> In-Reply-To: Your message of "Mon, 28 Sep 1998 10:08:45 MDT." <199809281608.KAA12061@Ilsa.StevesCafe.com>
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>Justin, > >I have been running an asus p2b-ds with -current for a week now, VERY >nice board! Am totally confused about the scsi term issue. Kevin @ atipa >said you worked out some of the details on this. I have a P2B-S here, and the last time I looked at this, it seemed that: 1) The termination settings I can set in the aic7xxx driver have no effect. All termination control is provided by some PLD that is controlled by the MB BIOS. 2) The MB allows you to toggle the termination on the low 8bits of the SE bus, but the high byte termination is always on (perhaps there is a jumper for it??) 3) The MB does not have automatic termination support. Since the P2B series uses an aic3860, the LVD and SE busses are electrically two separate busses. This is why you can use all three connectors simultaneously. > 1: the manual states: "The 68-pin WIDE SCSI connectoris always terminated > and will only work as an end device" > is that really true? yes. > 2: I want to put a wide device on the 68-pin wide (not u2w) bus, and > several narrow devices on the 50-pin bus. The BIOS doesn't have > the usual choice of "low off/hi on", only "off/on". If I turn the > SE term off, will it implicitly leave the 'high' side on? Or is this > even possible? The adaptec datasheet for the aha2940u2w board claims > that all connectors can be used simultaniously, so I think it should > work... You just need to turn off the low byte termination in the MB BIOS. > 3: Am I correct in believing that the uw bus and narrow bus are > effectively ONE SCSI bus, with the hi 8-bits left off one half? Yup. > 4: Kevin postulated that the BIOS actually enables/disables AUTOMATIC > TERMination, so that it should always be left on, and the hardware > will determine whats where, is that possible? This worrys me as > I have had "automatic TERMination" fail to work properly on other > MBs in the past, requiring a manual setting to function properly. The BIOS directly controls the terminators. There is no cable detection logic on this MB. -- Justin To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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