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Xref: sserve comp.unix.bsd:3811 comp.sys.ibm.pc.hardware:29328 Newsgroups: comp.unix.bsd,comp.sys.ibm.pc.hardware Path: sserve!manuel!munnari.oz.au!uunet!mcsun!Germany.EU.net!news.netmbx.de!zrz.tu-berlin.de!math.fu-berlin.de!informatik.tu-muenchen.de!rommel From: rommel@Informatik.TU-Muenchen.DE (Kai-Uwe Rommel) Subject: Re: Another Adaptec Question References: <7@tama.spec.co.jp> <1992Aug16.144341.24052@Informatik.TU-Muenchen.DE> <15776@star.cs.vu.nl> Sender: news@Informatik.TU-Muenchen.DE (USENET Newssystem) Organization: Technische Universitaet Muenchen, Germany Date: Mon, 17 Aug 1992 17:38:07 GMT Message-ID: <1992Aug17.173807.2309@Informatik.TU-Muenchen.DE> Distribution: world,fj,spec Lines: 54 In article <15776@star.cs.vu.nl> kjb@cs.vu.nl (Kees J. Bot) writes: >rommel@Informatik.TU-Muenchen.DE (Kai-Uwe Rommel) writes: >> >>In article <7@tama.spec.co.jp> amurai@tama.spec.co.jp (Atsushi Murai) writes: >>>ariticle is not ..but) and Fujitsu M2266SA 1.2 GB Disks. Functionality >>>is good but it looks like loosing a space about 200MB (above 1Gbyte). >>>And some guy let me know about this is a known problem of 1542B and >>>Adaptec will be fixed by new board - 1542C. (Oh well.....) >>>Now a day, A lot of guys try to run 386BSD with this card without know >>>this problem!!! >It has nothing to do with heads, sectors or cylinders. The group 0 SCSI >read/write commands allow only for a 21 bit block address limiting one >to 2 megablocks, which is 1GB at the usual 512 bytes per block. We don't talk about smart OSes like 386BSD :-) but the original poster asked why he doesn't see all the space under DOS/Novell. There it has to do quite a lot with heads/tracks/sectors ... >The group 1 SCSI read/write commands offer a 32 bit block address >however, but not all O.S.'s are smart enough to use those commands. > >>Adaptec has now a new mapping scheme with 256 heads and 64 sectors per >>track, [etc...] > >At least the 64 sectors per track number is wrong, you can't have more >than 63 sectors on a track. I don't like the 256 heads per track >either, I know of one (1.5GB) disk with an AT interface that uses the >top 2 head bits for two more cylinder bits. This limits the number of >heads per track to 64, but allows for 4096 cylinders. I don't know if >this is a normal way of addressing bigger disks under DOS. Anyone? Sorry, for those off-by-one errors, here is the original text from the Adaptec README file: --quote-- To eliminate the 1 Gigabyte limit, Adaptec's new extended translation feature uses 255 heads and 63 sectors, extending the disk drive capacity limit under DOS to 8 Gigabytes. --end-quote-- >I do not use the Adaptec BIOS by the way, there is a nice SCSI command >to ask the drive how big it is and that is all the info you need with >SCSI. You can't even see more than two disks with the BIOS. We may guess how DOS and Novell determine the disk geometry/size .. Kai Uwe Rommel /* Kai Uwe Rommel --- rommel@informatik.tu-muenchen.de */ DOS ... is still a real mode only non-reentrant interrupt handler, and always will be. -Russell Williams