Article 8511 of alt.sys.pdp10: Path: news3.best.com!news1.best.com!uninett.no!CensurBot.NetScum.Dk!newsfeedZ.netscum.dQ!netscum.int!news.algonet.se!algonet!cpk-news-hub1.bbnplanet.com!news.gtei.net!firehose.mindspring.com!news.mindspring.com!alderson From: alderson@netcom2.netcom.com (Richard M. Alderson III) Newsgroups: alt.sys.pdp11,vmsnet.pdp-11,comp.os.rsts,alt.sys.pdp10 Subject: Re: PDP-11 9-Track Tapes Date: 09 May 2000 22:41:30 GMT Organization: NETCOM On-line services Lines: 27 Distribution: inet Message-ID: References: <8epj68$4nf$1@info.cs.uofs.edu> <3910228B.49615006@trailing-edge.com> <8eq82h$qdu$1@newsmaster.cc.columbia.edu> <3910717C.768C59DE@trailing-edge.com> Reply-To: alderson@netcom.com NNTP-Posting-Host: c7.b7.09.66 X-Server-Date: 9 May 2000 22:41:49 GMT In-reply-to: Tim Shoppa's message of Wed, 03 May 2000 18:35:40 -0400 Xref: news3.best.com alt.sys.pdp11:6772 vmsnet.pdp-11:9806 comp.os.rsts:694 alt.sys.pdp10:8511 In article <3910717C.768C59DE@trailing-edge.com> Tim Shoppa writes: > TOPS-20 never was good at dealing with arbitrary tape formats. If someone > wants to correct me, and show me how to make a "tape image" program under > TOPS-20, I'd gladly listen. But I've had TOPS-20 system programmers tell me > that if you do unbuffered I/O, only core-dump format is possible, which means > converting the data, and if you use buffered I/O, you can't have a buffer big > enough to handle the largest records in core-dump format. This is all true. The problem is that tape buffers are taken from the Job Status Block, a monitor data structure, and are limited to 20 pages. A DUMPER-format tape written at the maximum blocking factor comes out to 24 pages per block if read back in as 8-bit bytes, so you can't get an arbitrary tape-copy program to work on Tops-20 due to size limitations. I once set out to create a version of Tops-20 with additional space in the JSB for tape buffers, to at least allow the copying of maximally sized DUMPER tapes (so that I could have more than one copy of a bunch of stuff). It's hard, a lot harder than it ought to be... Rich Alderson Last LOTS Tops-20 Systems Programmer, 1984-1991 Current maintainer, MIT TECO EMACS (v. 170) Customer Advocacy, XKL LLC, 1993-2000 last name @ XKL dot COM Chief systems administrator, XKL LLC, 1998-now Article 3498 of alt.sys.pdp10: Path: nntp1.ba.best.com!inwap From: inwap@best.com (Joe Smith) Newsgroups: alt.sys.pdp10 Subject: Re: File transfers was Re: Barb, DSKB is not in catalog! Date: 15 Feb 2001 10:33:33 GMT Organization: Chez Inwap Lines: 35 Message-ID: <96gb9t$2b97$1@nntp1.ba.best.com> References: <3A85706B.B4A96DC3@nospam.nospam> <3A8AE84B.99DF2D93@digiweb.com> <3A8AF157.6ABD1DE1@bartek.dontspamme.net> NNTP-Posting-Host: shell3.ba.best.com X-Trace: nntp1.ba.best.com 982233213 77095 206.184.139.134 (15 Feb 2001 10:33:33 GMT) X-Complaints-To: abuse@best.com NNTP-Posting-Date: 15 Feb 2001 10:33:33 GMT Xref: nntp1.ba.best.com alt.sys.pdp10:3498 In article <3A8AF157.6ABD1DE1@bartek.dontspamme.net>, Arthur Krewat wrote: >Hans B Pufal wrote: >> >> Good point, would it be possible with emulated tapes though? Attach a >> host file to a tape drive and ask TOPS-x to read it in, don't know how >> the formatting would work but the emulated tape drive can do format >> translations if required. >> >> Similarily on output, ask TOPS-x to output a tape and have the emulator >> write a host file doing any required reformatting. > >Having a dumb tape drive device determine filenames on the fly would involve >reverse engineering BACKUP. Sheesh. No, it wouldn't. TOPS-10 supported ANSI-labeled tapes. When creating a file on tape, the program could optionally use the ENTER UUO to specify a name to associate with the tape file. When reading a file from tape, a zeroed-out LOOKUP block could be used to get the name of the next file. BACKUP is not involved. PIP is. .COPY MTA:=*.* ; Copy files in current directory to tape .REWIND MTA: .COPY DSK:=MTA:*.* ; Copy files from tape to disk It doesn't take much programming effort to make a "dump tape drive emulator" look for 80-byte records. You'll find two or more records per block in tape file 3n+0 and 3n+2 (with data in tape file 3n+1). -Joe -- See http://www.inwap.com/ for PDP-10 and "ReBoot" pages.