Article 2164 of alt.sys.pdp10: Path: nntp1.ba.best.com!news1.best.com!newsfeed.mathworks.com!nntp.abs.net!chnws02.mediaone.net!chnws05.ne.mediaone.net!24.91.0.34!typhoon.ne.mediaone.net.POSTED!not-for-mail From: "D. R. Banks" Newsgroups: alt.sys.pdp10 References: <90fd0b$ecr$1@dbit.dbit.com> <3A2BAC15.5790632B@bartek.net> <3A2C05A9.EBB63F46@srv.net> <3A2C2948.C48E90D6@bartek.net> <3A2C2FBB.EB3C6E3B@bartek.net> <90imp6$c34$4@bob.news.rcn.net> <3A2D0378.B5F07323@bartek.net> Subject: Re: TU45... Lines: 74 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.50.4133.2400 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4133.2400 Message-ID: Date: Wed, 06 Dec 2000 18:32:41 GMT NNTP-Posting-Host: 24.218.2.13 X-Complaints-To: abuse@mediaone.net X-Trace: typhoon.ne.mediaone.net 976127561 24.218.2.13 (Wed, 06 Dec 2000 13:32:41 EST) NNTP-Posting-Date: Wed, 06 Dec 2000 13:32:41 EST Organization: Road Runner Xref: nntp1.ba.best.com alt.sys.pdp10:2164 Out of respect for everything that's decent, let's not say "TU7n." TU70s TU71s and TU72s came from Storage Technology Corp. TU78s came from garbage manufacturers. The STC drives were, in a word, brilliant. They were and are the only tape drives DEC ever slapped their nameplate on that I would trust useful data to. Sadly, DEC put a 100% markup on the drive (comparing bought from STC price vs. bought from DEC price), and instructed STC to never deal directly with DEC customers. Instead, DEC pushed those POS TU78s. An operator, trying to do a backup to a TU78 (often an exercise that was even worse than a waste of time) would often find that upon rewinding the tape, the stupid 78 couldn't read the tape label that it'd just written a few minutes before. For those not in the know, this was quite an achievement on the part of the TU78, as the 6250 BPI tape density had so much error correction that you could lose one track on write and two tracks on read and still get your data back. If one could buy a TU72 directly from STC, it'd have come at a cheaper price than what one would pay for a TU78 from DEC, but sadly, Digital's "Marketing" department took care of that. To be fair, although the TU70,1,2 drives were pretty inexpensive, the interface to the -10 or -20 wasn't. It involved a STC controller ('spensive) and a DX-10 or DX-20. The latter had wirewrapped components. The rumor was that Digital had only ever planned on selling 4 DX-20s, so it never bothered to setup a real manufacturing line for them. Whether or not that's true, one place I used to work had 10 of the only 4 DX-20s ever built. ;-) An interesting thing about reading blank tape: TOPS-10 would time out requests. If it issued a request and didn't get a response in about 3 mintues, it'd kill the request, and return "Hung device." A TU-70 could actually get to physical end of tape on a 2400 foot reel in that time (it being a 200 IPS drive). Trying to read a blank tape could exhaust the entire reel before getting a hung timeout. FWIW, from memory, TU-70 was 800/1600 BPI 9-Track 200 IPS, TU-71 was a 7-track drive, TU-72 was 1600/6250 BPI 9-Track 125 IPS. STC also sold a 1600/6250 9-Track drive that did 200 IPS (memory fades, but I believe it was their model number 3670), but DEC didn't have any channels that could reliably keep up with it. How times have changed. 6250 bytes per second at 200 inches per second turns out to be 1.25 megabytes per second (decimal megabytes). Today, we'd turn our noses up at drives that couldn't do that. The DDS-3 DAT drive on my PeeCee can handle 1Mb/sec uncompressed;2 Mb/sec compressed, and that seems slow. "Arthur Krewat" wrote in message news:3A2D0378.B5F07323@bartek.net... > jmfbahciv@aol.com wrote: > > > > >It doesn't really matter if you are past BOT on load, it will just rewind > > >the tape until it finds that shiny BOT :) So, load up on the take-up reel > > >all you want ... > > > > Welll....unless you have a runaway tape. Do not leave the > > tape drive to do it's own loading...ever. You could do that > > with TU7n, but that's because DEC didn't make them. > > > > I had a TU78 for my VAX-11/750, but it was THROWN OUT! > > ak