Chuck, As I am more interested in working with the tech and not reading a particular format the lack of support for other formats is okay. I would install mine in an IBM rack I have w/ some IBM 7532s and a bank leased line modems in it. I have to wait and see if I can find a good price on them. I've seen the Qualstar and Overland in the back of PC Magazine ads. They just don't seem as well built. When I look at them I get the feeling they were built for a finite number of years - enough for a company to migrate their data and that was it. I could be wrong but they seem to be all plastic units vs. the rugged construction on the HPs, or the Fujitsus. Heck even the Cipher desktops and the IBM 9438 look more solid than those guys.

On Aug 21, 2015 10:21 PM, "Ali" <cctalk at fahimi.net> wrote: or two connector Pertec interface? I am guessing two but better to ask than end up with a 200lb paper weight! A Fujitsu M2444AC should have two 50-pin connectors for a formatted Pertec interface. The 'C' suffix of that model number means that it is cached. The manual probably explains the details of how that works. I think it is basically a read ahead buffer during read options so if the host can't read data fast enough to keep up with the tape movement the drive can keep moving and reading into the cache until it fills up. That can eliminate a lot of back and forth tape repositioning with slow hosts. I had some Qualstar 1052 tabletop drives which were not cached. When used with a PCTD-16 ISA bus interface controller in a PC they weren't too bad since the PCTD-16 has its own on board buffer in the 256KB - 1024KB range. When used with a Q-bus Pertec interface in a PDP-11 they were a lot slower since neither the controller nor the drive had any real buffer space to help keep the tape moving. Much slower than the same system with the cached M2444AC instead.

Tom, Thanks for the heads up. I have dealt with Nico, and while a real nice guy, I doubt we could work out the shipping across the pond to make it worthwhile for either of us! :) -Ali

Al, Most of the units out there, short of the floor standing ones and the original IBM drives, are streamers, correct? Does this mainly apply to older tape? If I was using new tape would this be something of a concern? I've seen the 88780s in action and they are nicely built units. The Kennedy 9610 also seems very nice but the two on eBay are priced way out of my reach/hobbyist range. This answers my question indirectly. Thanks for the recs and the info. As I said originally this would be more for me to play with than to do any mission critical work. I would be using it on a PC system as a demonstration for the kids and maybe even for routine backup just because I can. Having said that I would like a solid unit that would last and req. minimal maintenance. I am okay with a rack system or a tabletop. The rack obviously would have the more retro feel but the tabletops are easier to manage. Ultimately I think it will come down to what I can find and at what price point. -Ali

On 2015-Aug-21, at 10:20 PM, Ali wrote: A brief conceptual overview: Vacuum-column and spring-arm drives comprise 3 servo systems: - each reel motor is in a closed servo loop with position sensors in its associated vacuum column or spring arm. - the capstan motor, driving the exposed tape between the reels, is in a servo loop with a tape-speed sensor, and externally controlled by commands for forward/reverse and speed selection. The 3 servo systems are electrically independent (in control terms and leaving aside power supplies). The connection between them is the tape. The vacuum-columns or spring-arms serve to implement a length of 'buffer' tape between each reel and the heads and capstan. The point of the buffer area is it is a very small mass of tape so movement of the tape over the heads can be started and stopped (by the capstan) very quickly. That is, it mechanically isolates the tape movement over the heads from the large mass of tape in the reels. Each reel servo acts on its own to simply try to keep the tape in the middle of its vacuum-column or its spring-arm in the center of swing. (It can be fun to play with the tape or arms while the drive is at idle and see how the reel motors respond, although one has to be cautious and delicate about doing so as the reel motors pack quite a whallop; and do so with a dud tape, not something that matters.) When the capstan receives a command signal and starts moving, the tape in between the buffer areas starts moving. The capstan speed servo acts to maintain constant linear tape speed over the heads. The moving tape upsets both vac-cols or spring-arms in the buffer areas in opposite directions, the reel servos now act to correct this upset. For example, when forward motion is called for, the capstan pulls tape out of the supply-side buffer (out of the vac-col or pulling the spring-arm tighter). The sensors in the supply vac-col or spring-arm direct the supply-reel motor to rotate to supply more tape into the buffer area. At the same time of course, tape is sent into the take-up buffer (into the vac-col or releasing tension on the spring-arm) and the take-up sensors and reel motor respond to rotate the take-up reel to pick up tape out of the buffer area. Pardon the elaboration, I just find it a very elegant design. When you see these drives in full-blown action, without knowing, you might think the control system to achieve what they do must be horribly complex, but with the 3 independent servo loops acting in coordination it's actually quite simple. (We'll leave auto-loading out of the discussion).

On 08/22/2015 10:07 AM, Jay Jaeger wrote: Historically, the two are very different in application. If you've got a COBOL handy on your tape system, try running the 1974 Navy Audit Tests, once the set of benchmarks by which CODASYL compliance of a vendor's COBOL was judged. (Al, do you have a copy of those on bitsavers?) Very short tape records were written and read back in one of the tests (I forget which one; it's been 40 years after all). Vacuum-column tape drives made the most itneresting noises as they went through their start-top tape motion. You could actually play melodies on some of them, simply by varying the block length. Vacuum-column drives, if you will, are inertia-trading devices. The reel motors are powerful in a 300 ips drive; they have to be. Practically speaking, it's not realistic to expect the system composed of the mass of the tape reels and the motors behind them to go from 0 to 300 ips in a fraction of a second--nor, to do it accurately. So, the reel motors handle the approximate movement of the high-inertia reel system and only maintain a few feet of loose tape, held in the vacuum columns, said short length massing almost nothing. The capstan(s) can then manage the quick tape movements quite nicely. The nature of the capstan mechanism varied between manufacturers--some used a pinch-roller sort of affair; the others used perforated capstans whose selection of nothing, vacuum or positive pressure could be managed quite nicely by a voice-coil valve. The point is that during the 50s and much of the 60s, diskless/drumless systems were not uncommon (anyone remember S/360 TOS?) and tapes were used as working storage. Sometime during the 70s, with the proliferation of disk storage, tapes became relegated to archival or offline storage, not working storage. Pick up a copy of Flores or Knuth on sorting and you can see how important tapes were for handling and manipulating large amounts of information. Comes the minicomputer and you begin to see spring-arm and direct servo drive units aimed toward the archival use of tapes--that is, a tape held information to be copied to a disk, so start-stop on a dime wasn't necessary. If one overshot a record, the drive/formatter only needed to bring the tape to a halt and read backwards until the gap before the desired block was reached, then back up another block or so and get a running start at the target. This change in role probably is what governed the brain-dead treatment of tape by later operating systems such as UNIX and PRIMOS, to name a couple. Until the advent of cheap cartridge tapes, almost all microcomputer OSes were utterly ignorant of the existence of tapes. --Chuck

On 08/22/2015 02:14 PM, Al Kossow wrote: I did find a reference to the CCVS suite of tests for sequential I/O: http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&iden… TOG lists the 1985 suite as the standard validation for COBOL, but the link goes to NCC and thence to a 404. One used to be able to get such stuff from the USDOC, but I doubt that they would know what you were talking about today. I suspect that there's a reel of tape somewhere with the damned things on it. --Chuck

On 08/23/2015 02:29 AM, jwsmobile wrote: I do remember CSPI. If you were selling to the USG, it was definitely in your interest to pass the Naval COBOL Auditing tests. Grace Hopper was largely responsible for their development and it stems from a morass of vendor "extensions and features" and the individual interpretations of the CODASYL standard that could render compilers different as night and day. It was apparent that some sort of test of conformity to the standard was necessary. FORTRAN suffered from the same problem also. In particular, I recall a CDC extension that seemed innocent but resulted in ambiguous syntax--a definite no-no in the world of languages. The PSR was never solved, as it would have required a change in an existing language. Note that these tests are not benchmarks--they merely serve to make sure that the compiler and run-time actually do what they're supposed to--and not what somebody *thinks* they should do. So these tests are historically important. I think all major compiler producers had specifications of that nature--they were also written for operating systems. Paper first, code later... --Chuck

On 08/24/2015 05:31 PM, steve shumaker wrote: Thanks for that--I ran into that one too. Considering that it's listed as a 9 track tape, how likely do you think that the good souls at NTIS even know what the heck that is--much less being able to provide it? --Chuck

On 08/24/2015 07:06 PM, steve shumaker wrote: I'll start by firing off an inquiry and see if they can stop laughing long enough to respond. --Chuck

On 08/22/2015 12:20 AM, Ali wrote: If you are buying a 30+ year-old tape drive, you WILL NEED the manuals! There may be setup options that need to be configured, or there may be something wrong with the drive. Obviously, you won't be buying a new 1/2" tape drive with factory warranty, and these things are both complex and finicky, compared to typical computer hardware. yes, a cheaper version of the vacuum column. usually used only on slower drives, but I have seen them up to 45 IPS. I've been looking for a SCSI 1/2" drive (or conversion boards for my CDC 92185's) for years. Never found one. I did rescue a SCSI to Pertec-formatted converter box off a scrap drive, and it WORKED the first time I powered it up, then the darn thing quit with a power on self test error! Arrgh! Jon