Date: 21 Apr 1998 05:32:41 GMT From: peter@netplex.com.au (Peter Wemm) To: freebsd-scsi@FreeBSD.ORG Subject: Re: ahh, I think I see part of the problem.. (CAM bouncing) Message-ID: <6hhb1p$7m7$1@haywire.dialix.com.au> References: <353cce7e.94813933@mail.cetlink.net>
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In article <199804202321.RAA17435@pluto.plutotech.com>, gibbs@plutotech.com (Justin T. Gibbs) writes: >>After reading this I don't understand what's broken about the 445S. >>Could you put it in more simple language? I have some 445C adapters >>and I wonder if they have the same characteristic. > > The 445S cannot properly transfer data to or from any address between > > (16MB * n) + BiosAddres > and > (16MB * n) + BiosAddress + BiosSize > > For n > 0 To be specific, this is a hardware defect on rev A - D cards. Rev E (which has firmware rev 3.37) does not have the problem. You (apparently) cannot use 3.37 firmware on the older A-D cards. Firmware rev 3.35 has an additional problem. Apparently the DMA counters are 24bit plus an 8-bit latch. This means that the bus-master DMA engine cannot DMA across a 16MB boundary. This means that the DMA "counter" wraps from 0x00ffffff to 0x00000000 instead of 0x01000000. This also happens at the 32MB, 48MB etc boundaries. Apparently the 3.36 firmware (for the A-D revision 445S cards) will do the transfer in one stage, reset the upper 8 bits and then do the second stage. I am not _sure_ if that upper 8 bit address is a latch or a counter that was missing the carry from the 3rd stage. There was talk of a hardware patch to the rev A-D cards to fix one of these problems, but I cannot remember the specifics and can't find my old archive of the stuff I downloaded. My gut feeling was that the wraparound was fixable in firmware (a simple matter of splitting a request), but the bios shadow problem was not. > I do not believe that the 445C has this problem. Yes, the 445C has none of these problems. The 445S are very old cards, mine was built in 1993. > -- > Justin To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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