Date: Fri, 4 Sep 1998 15:24:25 -0600 (MDT) From: "Kenneth D. Merry" <ken@plutotech.com> To: patrick@namesecure.com (Patrick Greenwell) Cc: freebsd-scsi@FreeBSD.ORG Subject: Re: AHC question Message-ID: <199809042124.PAA11050@panzer.plutotech.com> In-Reply-To: <Pine.BSI.3.96.980904125351.20720A-100000@po1.namesecure.com> from Patrick Greenwell at "Sep 4, 98 01:04:39 pm"
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Patrick Greenwell wrote... > > I have an Adaptec 2940UW hooked to a CMD-based subsystem. I have turned on > all enabled all the performance options for the ahc driver (tag-queuing, > SCB paging, and mmap I/O) option (FreeBSD 2.2.7-Release). boot -v offers > this: [ ... ] > Sep 4 04:37:48 test4 /kernel: low byte termination enabled, high byte > termination enabled > Sep 4 04:37:48 test4 /kernel: ahc0: aic7880 Wide Channel, SCSI Id=7, > 16/255 SCBs > Sep 4 04:37:48 test4 /kernel: ahc0: Resetting Channel A > Sep 4 04:37:48 test4 /kernel: ahc0: Downloading Sequencer Program...ahc0: > 417 instructions downloaded > Sep 4 04:37:48 test4 /kernel: Done > Sep 4 04:37:48 test4 /kernel: ahc0: Probing channel A > Sep 4 04:37:48 test4 /kernel: ahc0 waiting for scsi devices to settle > Sep 4 04:37:48 test4 /kernel: ahc0: target 0 using 16Bit transfers > Sep 4 04:37:48 test4 /kernel: ahc0: target 0 synchronous at 20.0MHz, > offset = 0x8 > > The question is how fast is this thing running? I am more used to BSDi > which states the max transfer rate when it is bringing the device up. I > have everything on the card and the CMD unit to do 40MB/sec. Does 20MHz == > 20MB/sec, or is there something I am missing? You're missing the fact that 20MHz * 2bytes == 40MB/sec. You probably won't get optimal performance under the old SCSI layer in 2.2.7, however. IIRC, you'll only be able to have 4 tagged transactions outstanding to the CMD array at any one time. CAM allows you to have as many outstanding transactions as the device allows. (we default to a maximum of 64 transactions, which is as much as most drives can handle, but you can easily make a quirk entry in the transport layer and push it up to 255 transactions) We've got a snapshot release from July 16th for -stable (which is what 2.2.7 is based off of), and we'll probably be coming out with another snapshot shortly. See: ftp://ftp.FreeBSD.ORG/pub/FreeBSD/cam/README Ken -- Kenneth Merry ken@plutotech.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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