Magnetic Media (Floppies and Tapes) - Computerphile

Before flash memory became commonplace, people relied heavily on floppy disks to store their data. Dr Steve Bagley takes us through the basics of magnetic media.

This video was filmed and edited by Sean Riley.

[kevind]

Please, a followup video to show how magnetism is used to turn bits on and off, and why magnetic tapes/discs deteriorate over time.

[NotMarkKnopfler]

Great to see smalltalk mentioned. As the first object oriented language written in itself it was decades ahead of its time. Even now there's nothing quite like it. It would make an excellent subject for a video.

[MaizumaGames]

I'm kind of disappointed. The guy spend a lot time describing how things rotate and how heads magically read magnetic data... I was expecting to hear about the actual read/write process. Sensors and precise numbers, speed comparisons, etc.

[VerySimplyMS]

Floppy Disc? You mean the save logo?




:^)

[NeilRieck]

Back in the day, I worked on a PDP-11 system which employed a TU-58 tape drive. The media was "block structured". These tape drives were also present on all VAX-11/730 machines to load the microcode during boot.

[DrRChandra]

While Compact Discs start at the spindle and spiral outwards, the numbering of floppy and hard disk tracks generally starts at the edge and increases towards the spindle.

Audio Compact Cassettes (audio cassettes) normally have the supply reel on the left and the takeup reel on the right. The shown animation must be of a reversing deck :-) Love those autoreversing ones; gets to the end of the tape, senes the reels aren't moving, flips the head around, and starts rotating the reel on the left and the capstan in the opposite direction.

[xwolpertinger]

Q: "What's Smalltalk?"
A: A good topic for a video

[Nuklen]

In a late 90's computer magazine I saw a review of a device that'd let you store data on a VHS tape. It let you store quite a large amount of data on a relatively cheap format, but the machine was expensive and it was slow as molasses.

[ryanburnside]

One thing I like about technology is that it doesn't really get outdated. Sure the actual devices might become obsolete but the knowledge that makes them work the real "technology" can be used in strange new ways any time it fits the bill. It is very frustrating how careful marketing has directed consumers' definitions about technology. It's not the device, it is the study of the principles that make the device work. Too many people say they like technology but really just love consumer devices and would be bored to tears learning the technology itself.

[AlRoderick]

Music CDs were designed for constant linear speed, so the disc spins at 200 rpm near the rim and 500 rpm near the center. This wasn't a problem for music all read in order, but when you got to CD-ROM the drive would speed up and slow down constantly when it skipped around the disc. Eventually the constant speed drive became standard, and the drive would just read data slower closer to the center rather than speed up.

[goeiecool]

I would like to see a followup explaining more about the read write mechanism. And also an explanation of why punching a hole makes a disk double sided.

[clangerbasher]

Old movies? I earned a good living looking after a few thousand of those tapes.

[shmehfleh]

Yep, linear tape is still a popular format. The most common format these days is LTO, or Linear Tape-Open. Modern, generation 7 LTO tape carts can hold up to 6TB of uncompressed data, with 12, 18 & 48TB capacities on the horizon. LTO cartridges have only one spool, so the tape drive contains a take-up spool internally. Data is written on the first track from the beginning of the tape to the end, then written on the second track from the end back to the beginning. Data continues to be written in this serpentine fashion until all tracks are full, and the tape has been wound back into the cart.

[iuxgjve]

at 8:38 How is that connected to previous question?
It answers why read/write speed is the same for inner/outer tracks, not how much data is stored.

[lohphat]

IIRC the Apple IIe floppy drives used a variable-speed spindle for its floppies so the outer cylinders could have more sectors per track.

[codebeard]

How does the drive know which sector it is reading? Is there a special area somewhere on the disk that it can detect as it goes round?

[WickedMuis]

I was hoping to see an explanation of the technical side a bit of magnetic data as well, on a molecular level. I know that these pieces of rust on the tape are like small magnets and the direction they are standing defines whether it will be read as a 1 or a 0, but would have loved to see a more in-depth explanation.

[kinpatu]

I'd love to see an episode on core rope memory.

[chris_]

This is awesome! Now I'd love to see a video explaining how SSDs work—or would it be essentially the same as the video on "How Computer Memory Works"?
Thanks!

[isaacsailor]

Could you do a comparison between HDD and SSD data storage methods? Is there a why to visually describe the disk access speed between the two storage types?