Path: utzoo!utgpu!attcan!uunet!lll-winken!lll-tis!ames!ucsd!ucsdhub!hp-sdd!hplabs!hpl-opus!hpccc!hp-sde!hpfcdc!rjn From: rjn@hpfcdc.HP.COM (Bob Niland) Newsgroups: comp.unix.questions Subject: Re: Writing HP cartridge tapes on a Sun 3 Message-ID: <5740026@hpfcdc.HP.COM> Date: 7 Aug 88 19:10:46 GMT References: <614@ednor.UUCP> Organization: HP Ft. Collins, Co. Lines: 89 re: "Does anybody know if it is possible to produce a tar tape on a Sun that is readable on an HP 300? It seems that the HP uses some kind of strange format..." from a Nov 1987 response to a similar question... re: HP vs SUN format on 1/4-in. cartridge tapes The sad news: Sorry, you can't use 1/4-in. cartridge tape to exchange data with non-HP systems. Why? Read on... As far as I know, there is no formal industry standard for 1/4-in. tape formats, like the ANSI standards for 1/2-in. tape. The variations between vendors may include: number of tracks, density, speed, direction, encoding, etc. The predominant HP standard is the 3M HCD-75 format, code-named "Linus", as used on 88140LC/SC media (this is what you have). A few vendors have adopted QIC-02/24. The HP 9142A drive uses "PCT" format, also incompatible with HCD. The HCD-75 format was developed in the early 80's (well before QIC). I have no idea why it never became a standard outside HP. It's rough specifications are: 10,000 cpi, 16 track, MFM encoding. The media is pre-formatted by 3M into 1536-byte blocks (1024 data bytes plus 50% redundancy for error recovery). The 1.5Kb blocks are delimited by full-track "keys", written by 3M. The 3M designation for the 150-ft. HP88140SC is DC615HC, and the 600-ft. HP88140LC is DC600HC. There is also a new HCD-134 format and "XTD" media, suitable for 32-track drives. The keys pre-formatting is critical. It can be done only by 3M. The "certification" process done by our 'sdfinit' and 'mediainit' commands only erases, verifies and spares the existing data frames. It DOES NOT create new keys or frames on a blank tape. If you degauss an 88140 tape, or write on it on a non-HCD-75 system, you destroy it's useability on HP systems. This is why the reels are often labelled "DO NOT DEGAUSS". SUN apparently uses QIC-24 format on QIC-02 drives. I don't have complete specs at hand, but what I could find says: 9 tracks, NRZI encoding and variable length records. SUN media appears to be 3M DC300XL. The density must be similar, since a 600-ft. 16-track HP tape holds 67 Mbytes, and a 600-ft. 9-track DC300XL holds 45 Mbytes. In any case, I know from personal experience that DC300XL media doesn't work in 88140-compatible HP drives. Now, what can happen if you attempt interchange? 1. If the SUN system manages to write on your HP tape, the tape is ruined for further HP use. You may be able to use it on the SUN after formatting it on the SUN (or whatever process they use to prep tapes, if any). Why would the SUN write on it? Well, on HP tape drives, my understanding is that the drive will update the CS/80 logs on the tape (outside the region of data frames), regardless of whether or not the tape is write-protected (I doubt HP drives will write on a "foreign" tape). Unless you deliberately write on it, I don't really think a SUN will trash the tape. QIC format does not allow selective re-writing of records like the HCD-75 format does. There are probably also no "logs" because QIC format relies on read-while-write to prevent errors and has no other error recovery mechanism, and thus no use for logs. 2. The tape may be left rewound in a strange state. Apart from the fact that SUN rewinds to the opposite end of the media from HP, the BOT/EOT conventions are different. The physical beginning and end of tape (BOT/EOT) on these cartridges is several holes punched in the tape, sensed optically through the little mirror opening in the cartridge. The tape is NOT affixed to the takeup reels. It is possible to rewind the tape off the hubs, so the drive firmware is "cautious". HP drives do not use the optical sense method; it was not sufficiently reliable. We use the boundary keys to determine BOT/EOT, and always rewind the tape before unload/release. If the tape is rewound to the BOT/EOT holes, it is outside the keys area, and the HP drive will probably time-out looking for keys, and thinks that the tape is spilled (or about to). It will buzz and reject the cartridge to avoid damaging the tape by further attempts at tape motion. If you can see that the tape has not unspooled, you can try manual repositioning. Wind the tape into the normal HP "rewound" state. Watch carefully for the first BOT/EOT hole. Park the hole toward the emptier reel (with respect to the mirror), plus an extra foot or so. Be careful not to dump the tape. It is very tricky to disassemble and reload one of these cartridges. Regards, Hewlett-Packard Bob Niland rjn@hpfcrjn.HP.COM 3404 East Harmony Road [hplabs|hpu...!hpfcse]!rjn Ft Collins CO 80525-9599