ken@dali.gatech.edu (Ken Seefried iii) (12/06/90)
In article <448@camco.Celestial.COM> bill@camco.Celestial.COM (Bill Campbell) writes: > >I have a related question here. I formatted and installed Xenix >2.3.2 on a machine using and Adaptec 1542b with a Wren Runner >hard drive. I then put this hard disk into a Tandy 4000 with an >older Adaptec 1540 (the original Tandy version without the >connector on the back). I then had to re-install Xenix from >scratch since the disk couldn't be read by the older controller. > I have seen this also. There is obviously some difference in the way that the older controllers and the newer ones see the disk. 'Course...noone has ever guarenteed this sort of thing to work, so I didn't get to upset when it happened to me. -- ken seefried iii "A sneer, a snarl, a whip that ken@dali.gatech.edu stings...these are a few of my favorite things..."
chuckl@chips.com (Chuck Linsley) (12/07/90)
In article <448@camco.Celestial.COM> bill@camco.Celestial.COM (Bill Campbell) writes: > >I have a related question here. I formatted and installed Xenix >2.3.2 on a machine using and Adaptec 1542b with a Wren Runner >hard drive. I then put this hard disk into a Tandy 4000 with an >older Adaptec 1540 (the original Tandy version without the >connector on the back). I then had to re-install Xenix from >scratch since the disk couldn't be read by the older controller. One common difference between host adapters is a different algorithm for converting cylinder-head-sector (CHS) disk addresses to SCSI logical block addresses (LBA). (Even with *NIX, the INT 13H routine is used at boot time, until the OS's driver is read from the disk. INT 13H uses CHS addresses.) If the host adapters use different algorithms for the conversion, the new BIOS will look for the data at a different location on the disk than the old BIOS wrote it. Some adapters do the conversion based on the drive's real physical geometry, but INT 13 has a limit of 1024 cylinders, and many large SCSI disks are bigger than this. So, some host adapters fudge the conversion so that the entire disk will be usable. There is no standard way of doing this. The SCSI CAM (Common Access Method) addresses this, as well as many other issues, but even after it becomes real, there will still be problems with older boards, until they all die of old age. Chuck Linsley chuckl@chips.com Chips and Technologies, Inc. Mass Storage Operation