Do you know HOW a COMPUTER TAPE DRIVE REALLY Works? 1968 Phase Encoding IBM 2420 NOW Technology
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- Опубліковано 5 лют 2025
- Very Technical Computer Magnetic Tape Recording Info, circa 1968.
This Technical training film describes the IBM 2420 magnetic tape drive, introduced with the IBM System/360 in 1964. The 2420 improved System/360's throughput by providing faster tape speeds, better access times and superior rewind ability. The film describes significant improvements in the 2420 Tape Drive system including "Phase Encoding" technology. Illustrations and diagrams are included as well as high definition views of the tape mechanisms. An excellent instructional training aid and historical reference. Terms and concepts include magnetic tape transport, tape “skew”, bit encoding, parity and parity error, recording reliability,
The concept of FCP, “Functional circuit packaging” is mentioned. FCP is the process of encapsulating semiconductor materials into a protective case to create a functional circuit. A process is also known as integrated circuit (IC) packaging.
Other Discussions include:
Advancements in 2420 model 5 and 2420 model 7 machines, using 9 Track Tape, Cartridge Loading Mechanisms, with 10.5 inch reels.
The NRZI, “Non-Return to Zero, IBM”, term is also explained.
Run time 16 mins. Uploaded by Computer History Archives Project - CHAP, for comment and discussion, and reference
2k and 4k Stock Footage available from Periscope Film
www.periscopefi...
For more information on IBM Magnetic Tape Drives
visit:
www.ibm.com
Tape drives were their own type of BlinkenLights. Some of the best physical action to watch on a mainframe. I loved writing programs to read and catalog inter-record and inter-block gaps. :D Thanks for another home movie!
My first job out of college was at C J Kennedy Co. designing 1600 BPI, PE drives. They made versions for minicomputers. This made it possible to exchange data between mainframes and smaller labs that had minicomputers. Was a great job doing low level analog signal work, digital design, and power servo design. That wide range of engineering experience served me well until I retired.
Hi @doug6763-h6y, sounds like you have some great experience there! Thank you for sharing that!
Excellent film on tape drives of the era. Thank you, CHAP, for once again uploading a wonderful piece of tech history.
Glad you liked it. I appreciate the feedback. (At least there is a good video reference on the 2420 tape drive now, in case someone wants to buy one...) Next week, hope to post a video on an early graphics terminal of the 1960s. Film is still in the editing stage..
Bloody brilliant. Thank you CHAP.
Hi @frankowalker4662, thank you! Glad you enjoyed it!. ~ VK
Yes. I'm that old.
I remember the Time Tunnel Syfy TV series had tape drives in the background along with just about ever other science fiction TV show and movie in the 60s.🤠
p.s. Now I understand why I would see a few rows of "00" at the beginning of a program when looking at the HEX editor. 😮
Hi @bblod4896, yes, good memories of T-Tunnel too! Pieces of the giant SAGE computer in the background. An Irwin Classic. ~ Thanks!
I used to be a computer tech for a telecom company. There was one occasion when a TV station was filming one of the systems we had. They didn't think the tape drives looked busy enough, so we ran diagnostics on them, so they looked like they were doing something. 🙂
@James_Knott
Brilliant!
I learned NRZI as Non Return to Zero Inverted.
I was a computer tech back in the 80s and worked a lot with tape drives, mostly Data General.
Yes, and sometimes called "Non Return to Zero, IBM." Have seen it written both ways.
Yep. I heard the NRZI and immediately thought No, its Inverted not IBM. But I remembered that the whole world was IBMs to name and control in those days. No competitors name or their usage name, designs or product existed within IBM, it was forbidden. We just called the drives IBM compatible. As they were often used to transfer data from a local production or accounting computer to a commercial data centre mainframe for processing in addition to storage and backup. Not much was done via a telephone wire and there was no internet or wifi.
Also, while tape skew was a problem, a major cause was engineering tolerance on the recording head itself in the alignment of all the 9 bits. The physical location of all 9 recording gaps needed to be adjusted for in drive setup as well as in the drive firmware. The higher the recording density the tighter the tolerances needed to be or any track could put its 1 or 0 in the wrong line, including the parity bit.
@@jimspc07 Actually, aligning a tape drive head is something I have experience with. Back in the 80s I was a computer tech. The procedure, at least on the drives I worked on was to use an alignment tape and then adjust the entire head so that on read the bits were aligned as close as possible. Then, write to a scratch tape, while adjusting the delay to write each bit so they lined up properly. Those heads had read after write, so you could monitor this. It also allowed the data to be verified as it was written.
@ Yep. Adjusting the 'one shot' I think think was the term. But wow it was so looooong ago Maybe i'm thinking of something else.
But doing it on site was a real pain. Some of the drives we had were small and we could take the whole unit back to the workshop after connecting a loaner. That was picked up when the call came in as a precaution. That was always better than lugging a scope and tapes around, and on site everyone was wanting to know how long you would be, one after the other.
But whatever. Thank goodness for USB sticks.
@@jimspc07 Fortunately almost all the systems I worked on were in our office. Most in "Data Central", though there were a few upstairs in the Air Canada reservation system and a couple in a stock brokers office, a few blocks away. I know about the pressure in that job. On one occasion I had to go out to Edmonton, from Toronto. I was able to correct the problem in about a half hour. Then the regional manager asked me when I'd have it fixed and I told him it already was. I then packed up and took the next flight back to Toronto. That was Toronto to Edmonton and back in a single day! That's almost 3400 miles of flying!
This is the best film yet that I've seen on IBM tape drive technology. I even got a glimpse at the rare 2415 drives that I was so fond of back in the day. However, a question - near the end, at time index 17:33, I'm seeing cabinetry that I've never seen before: while it is obvious that there's a 2420 inside, the front of the cabinet is strange and the control box face is black. What are these? Where were they used? Thanks.
Hi @Mossy-Rock, greetings. Thank you for the great feedback! Will have to see if we can identify the cabinets and control box you pointed out. Perhaps also one of our viewers can help with identifying their use. Thanks the observations! ~ VK, CHAP
Surprised to see that "phase encoding" actually meant something - I thought it was going to be like Sega's "blast processing"! 🤣
Actually, it's commonly used in telecom. The dial up modems often used quadrature modulation, where signals at 90° apart were combined to produce a waveform at various phase angles and amplitudes. These days, 5G uses phase shifting for beam forming, where the signal is formed into narrow beams that can be aimed at where the phone is.
I wish we still made stuff like this here in the US
You would not find a market for stuff like this. You have data farms and social media. They all have "made in china" or other low cost production hardware. All outsourced by your own big tech companies to cut costs, they also outsourced their profits inadvertently.
Also today its ironic the production is very much automated and robotic so where something is made is irrelevant in cost. Robot x works for the same price in any country. The ancillary input costs today are also not much different, but different enough to keep production off shore.
You can fabricate computer chips in the US. Pack them up and send them to Indonesia or Vietnam or China among many countries to be assembled into the Computer chip packages we can buy, then send them back assembled and its supposedly more economical than doing it all at home. Even on the US $7 per hour approved yet unlivable rate.
I would suggest it has more to do with business being able to shift money around the world to avoid homeland tax though. After years of getting rules and regulations changed bit by bit year by year. That's US big business in operation, allegiance to no one except themselves, not even their shareholders.
Ah, I'm guessing that this is the next generation of drives that replaced the IBM 729 series
I was hoping to see more of the lady in the advertisement
We are looking for "live" video of her as well. Thanks!
@@ComputerHistoryArchivesProject Excellent
420 tape drive, 420 viewer. yes.
Yes, and apparently, the 420 drive runs quite smoothly, unless it encounters stems or seeds in the capstan drives. : )
@@ComputerHistoryArchivesProject Yes, and be sure to take care of the HEADS, Maaan! 😊
🌿🥇🏆🌿 First!
Confirmed : )
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ok