Multiple floppies in one system?

Option #2 is a better way. Leaving an unpowered drive on a drive chain can create problems, since the divers are not properly tri-stated, or drive high for open collector lines.

I'd use a double pole double throw switch. Run the two drive select lines to the center contacts, and top two pins to the two drives you're most likely to use at one time, and the bottom two pins to the other pair that are most likely to be used together. Note that you'll want to keep these runs as short as possible. The drive select lines are, IIRC, the middle two wires of the group of four that's typically twisted in a floppy cable. The original IBM AT (and possible XT, I'm not sure) were the instigators in using the twisted cables. It was cheaper to have a Tiawanese cable house make the cables than it was to address the issue of "well, if you want drive A:, you have to unjumper DS1 and move it to DS0. But drive B: has to have DS1 jumpered." From a customer support standpoint, and being able to send drives out, it meant they could pre-configure the jumper for DS1, and be done with it. There are some other approaches: There were some after market cards that support 4 or 8 drives (8 drives as two controllers, which took extra software). IIRC, the BIOS actually has support for 4 drives, but it's the drive select lines that become the issue. I don't have my Book O' Magic Registers handy, but I think IBM left out the other control bit in the drive control register. It may have only been some old 486 and lower motherboards that supported 4 drives, by making the extra drive select bit available in another register. Once manufacturers realized that no one ('no one' being all but the 4 or 5 people a year) wanted 4 floppies in the system, support for it was dropped. If you ever only need one drive at a time to be active, you could use a rotary switch, and switch the drive select line between any of the four drives. Note that putting more than 4 drives on a chain isn't a good idea, since the bus drivers start getting near their loading limits. Those extra signals, even tri-stated, present a bus load, and add capacitance to the signals. What would be slick is to setup some kind of "fast swap" bay, where you plug the drive you want into a carrier, much like these removable IDE drives. Sadly, I doubt any such thing exists for floppies, since for all practical purposes (from a consumer standpoint), floppies are nearing the end of their life span. What with bootable CDs, CD-R, CD-RW, DVD, and the incredibly small capacity of a floppy, I predict they'll be a rare item in 10 years, and only used to support the old collectables. Just try and find 5.25" low density disks anymore. --John