simH Migration

We have already migrated IRIS from an old backup tape into simH, which is what is now available in the downloads area as a Diablo 31 and a Century 114 drive. This info is supplied for anyone who comes across an IRIS backup tape and is able to read it into a binary file on Windows. Alternately, you can contact me for assistance.

We would love to have more versions of IRIS up and running!
If you know of any backups still in existence, please let us know.

Some challenges of migrating IRIS to another LU0:

  • IRIS never really addressed the challenges of migrating from one disk drive type to another.
  • Before booting, the driver for LU0 must be embedded in both CONFIG and REX, with an alternate version inside the boot sector zero.
  • Driver tables in CONFIG must reflect the new driver data.
  • DMAP is always located on Track 1 Sector 0. Which means if you migrate to a drive with a different number of sectors per track, DMAP will move, and most likely clobber another file.
  • DMAP on LU0 is rebuilt every IPL, and is the 1st file mapped for usage. Whatever it overwrites will be lost.

Additional challenges of migrating to simH:

  • simH requires that all DKP drives must be device 33.
  • Only certain DG drives are supported on simH.
  • Very few drivers existed on IRIS for standard DG controllers using Device 33
  • Any backup binary file may contain a tape utility header.
  • A backup binary file may have reverse endian coding (all bytes swapped in words).
  • simH automatically extends DKP files when blocks are accessed past EOF, making it harder to establish proper size.

Our Diablo 31 (D31) LU0 contains a utility (XGEN) designed to assist in some of these areas.
For purposes of this explanation, we will assume a binary file on Windows (MIGRATING.BIN) that contains an IRIS LU0 which originally had 16 (dec) sectors per track. Since the 6103 drive supported by simH has the same # of sectors per track, we will migrate to that.

Warning: Always backup both the working IRIS drive and the target binary file. It is very easy to damage either one beyond repair. Backup can be done via a Windows Copy and Paste of the drive file.

Step 1: Isolate a valid IRIS LU from the binary file.
Step 2: Prepare file for Actual Install
Step 3: Import Drivers for LU0 and Boot it


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