this post was submitted on 23 Oct 2024
341 points (98.6% liked)
Technology
59148 readers
1986 users here now
This is a most excellent place for technology news and articles.
Our Rules
- Follow the lemmy.world rules.
- Only tech related content.
- Be excellent to each another!
- Mod approved content bots can post up to 10 articles per day.
- Threads asking for personal tech support may be deleted.
- Politics threads may be removed.
- No memes allowed as posts, OK to post as comments.
- Only approved bots from the list below, to ask if your bot can be added please contact us.
- Check for duplicates before posting, duplicates may be removed
Approved Bots
founded 1 year ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
It's kind of an elegant hack IBM did to make floppy drives easier to bother with.
Floppy drives were designed to attach to the computer in a bus topology, sharing all of their data connections. The only wires that weren't in common were the Motor Enable and Drive Select lines, which is how the computer would tell the drives which one it wanted to talk to. This meant the drive needed to know which drive it was, so there were jumpers on the back so you could set them up as Drive 0 or 1 (which would show up in DOS as A or B). By twisting seven cables (three of which were ground and weren't effected) and jumpering all drives as Drive 1(B), drives attached before the twist would respond as drive B and after the twist as drive A. That way you didn't need to fuck with the jumpers. Some later drives even did away with the jumpers and hard wired them as B.
Thnx for this exposition!