Handling four floppy drives

[Ruud]

Last time I needed 4 floppys I simply installed an Adaptec AHA-1542CF SCSI controller and set its floppy port to act as a secondary one...

This remark made in another thread triggered the question: what is actual needed to be able handle four drives?

I know a XT can handle four drives. Or in fact: MS-DOS can handle four floppy drives when using a XT. (side question: what about FreeDOS, DR-DOS?)

But the above Adaptec is a 16-bitter. Timo, my main question, did you install in a 286+? I always thought that that was not possible because: how does the PC know/remember what type these extra drives are?

But if placed in a XT, I think at least a driver is needed because, AFAIK, the BIOS doesn't support a second FDC. I know there is an I/O range reserved for a second FDC but it is not mentioned in any XT BIOS I am familiar with. This raises the question, can a 286+ BIOS handle a second FDC? But then again: what about saving the info in the BIOS?

Regarding the driver, I read something about one in another thread but cannot find it now. A pointer is welcome.

Thank you for any info!

 

[maxtherabbit]

the only PC BIOS I've ever seen that can (ostensibly) handle a secondary FDC is the MR BIOS

I wasn't able to make it work on my setup however, nor have I found someone yet who did

 

[Timo W.]

It was a Windows 95 machine, actually. I still have it running incl. the Adaptec, but it no longer has 4 floppy drives. I had the floppy type for the 3rd and 4th set via MS-DOS. I'm pretty sure the 1542CF has additional code in its BIOS to make the controller working as a secondary one, because setting primary/secondary can only be done in the BIOS of the 1542CF, not via a jumper, indicating it won't work if you disable the controller's BIOS.

 

[Chuck(G)]

I have a system with 6 drives installed; all are accessible as DOS drives. I use three Microsolutions Compaticard IVs. If I had room, those 6 could be 12. Maybe I'll dig into my box of FD 505s and replace all of the drives and get my 12. Oh--each of the CCs are on different ports, IRQs and DMAs (the limiting factor).

 

[maxtherabbit]

clearly with option ROMs or installable device drivers the possibilities are endless, but I was referring only to the motherboard's BIOS

 

[Chuck(G)]

I've got several later systems that support only a single floppy drive. With a DOR add-on card, it should be possible to extend that to 4 drives, since the PC platform doesn't use the 765 drive select outputs. Doing it on a PCI-only system is probably a bit more daunting, however.

 

[whartung]

TRS-80s used to be able to use 4 drives, but at 80K per drive, you needed all the storage you could get.

 

[channelmaniac]

I have a Compaticard IV in my IBM PC/XT system with a 5.25" 360K, 3.5" 1.44M, and a 5.25" 1.2M floppy drive. Works well and has a utility that lets you remap the floppies so your hard drive can be C:\