On Tue, 25 Jun 2019 at 07:31, Lars Brinkhoff <[email protected]> wrote: > > Hello, > > Some of DEC's disks allow reading and writing the sector headers. ITS' > disk formatting program, SALV (the Salvager), uses this to make a new > file structure on a pack, and to verify its integrity. > > This isn't fully supported by SIMH. The file PDP10/pdp10_rp.c has the > comment "23-Aug-01 RMS Added read/write header stubs for ITS", and the > stub is in "case FNC_WRITEH" in rp_svc. It's a no-op that just sets the > DONE flag. > > What is supposed to happen is that SALV wants to write two header words > with geometry information and then the sector data with a particular bit > pattern. The verification phase reads back and checks the bit pattern. > Since those bits aren't written, the verification fails. > > This isn't so bad since SALV offers to skip the verification. But now > this has come up again using Rich Cornwell's upcoming KA10 addition to > SIMH. The KA10 version of SALV does the same with an RP04 disk, but > does not have the option to skip the verification. SALV also writes > some information to the key fields in the headers, which is later read > back. > > I'm wondering what your opinions are reagarding this? I see some options: > > 1. Do not change SIMH. Patch SALV to skip the verification. Obviously > this is quite quick and painless, but leaves me with a slightly > dissatisfied feeling. Some historical software isn't running properly. > > 2. Add header words to the disk image file. An incompatible change, but > should of course be optional. > > 3. Store header words out of band somehow. Last in the image file? > In another file? > > I understand the case for making changes to SIMH is quite weak if > running SALV is the one and only use case. Are there any other programs > that reads or writes the headers?
How about storing them only in memory - still an incomplete implementation, but should be enough to pass the SALV tests... Could always be extended to persist them later David _______________________________________________ Simh mailing list [email protected] http://mailman.trailing-edge.com/mailman/listinfo/simh
