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I would like to add a 5.25 floppy to a Pentium 4 computer

T

Twospruces

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Looking for suggestions on how to accomplish adding an additional 5.25 floppy to my ASUS P4P-800 deluxe computer.

Bios supports only ONE floppy of any kind.

My ideal configuration is
1) 5.25 1.2MB floppy
2) 5.25 360K floppy
3) 3.5 1.44MB floppy

For (1) I can directly mount it in the PC
for (3) I can use a USB 3.5 inch floppy. the BIOS supports this

for (2)... I need some kind of additional controller.
Any ideas?

thanks!
 
I have looked at the FC5025 USB controller - it doesn't add a floppy in the normal way. It lets read disk images but it does not make the drive accessible in the normal way to the PC.
 
You'll need to find a motherboard that supports two floppy drives if you want to have 3 drives. There are no PCI/PCIe floppy controllers that add "native" floppy support. Some USB floppy drives can work as a normal 3.5" drive if the BIOS supports it.

Your only option for such a configuration would be a motherboard that supports two floppy drives and using an LS-120/240 for the 3.5" drive.
 
What are you going to do with the 5.25" floppy drive? On a P4, I don't assume you are going to run old software in DOS from real disks. If all you want is to read or write disk images, you can buy or build a Greaseweazle, which is a floppy controller for USB. It's not going to give you A: or B: drive letters to access the drive(s), however.
 
Since I rarely use a floppy drive via BIOS access, I keep a Socket 939 system around with a really good floppy controller (does FM as well as 128 byte MFM) and use a switch to a back bracket (described in this forum) to switch between the internal 1.44M drive and an external (DC37) drive.

Just saying that most folks don't need two drives at the same time.
 
I could implement a switch, yes, and reboot/tweak bios whenever I want to change drives. agreed.

The main use case is to be able to write downloaded images to floppy.
 
krebizfan said:
Another option would be to have a switch for the two 5.25" drives. It is unlikely that one would need both 360K and 1.2MB drives at the same time.
https://www.seasip.info/VintagePC/floppies.html shows one technique to have two drives share a single cable position.
Click to expand...

thanks for that link. So, the DRIVPARM command can let me switch drive types without rebooting. That sounds good. I could write a batch program to make that a bit easier.

If the BIOS only supports a single floppy drive definition.. I wonder if DRIVER.SYS could take care of that? I might be able to add another floppy even when the BIOS does not support it?
 
DC2.SYS and SDRIVE.SYS are looking for specific controllers.
My mainboard silicon only seems to support a single floppy, period.

I have not found a software solution that allows a 2nd floppy to be added.

What I have proven to myself is that both floppies can sit on the same cable, and I can jumper one or the other to be available.
I use the "D1" jumpers; One drive gets D1 jumper, and the other does not.

So, it seems the only way to solve having both types of 5.25 inch floppy drive on this mainboard is to reboot, modify the bios settings, and physically select the drive I want.

Unless I can find some kind of secondary floppy controller on a PCIE card?
 
Your motherboard doesn't bring out the extra drive select and motor control lines anyway, so you're limited to a single drive by dint of this fact. One of the marvels of penny-pinching LPC packaging...
In the bad old days, some got around this by adding a small ISA card daisy-chained off the regular floppy controller. Said card simply provided a latch at 3F2 for the extra drive select and motor control, since that register is write-only. Bring those and the rest of the floppy signals out to a DC37 connector on the bracket. You could support up to 4 floppies that way. When ISA departed for bus heaven, that scheme didn't work. Some SuperIO chipsets allowed for reconfiguration of the (normal) printer port signals to support an additional floppy (the printer port was disabled). You'd often see this on some laptops.

You could, I suppose, go the "switched" drive route and plug the drive type in BIOS RAM and then use DRIVER.SYS to do the rest of the work. I don't think most BIOSes read the drive type from CMOS after boot.

Of course, that scheme goes out the window with Windows NT and 98+.
 
Last edited:
Twospruces said:
Unless I can find some kind of secondary floppy controller on a PCIE card?
Click to expand...

No such device exists, as I've already said. It's not possible for such a device to exist because the floppy drive is married to the ISA bus, or the LPC bus (a subset of ISA). It also requires BIOS support. None of these things are possible on PCI or PCIe. The vintage computer community has pined for such a device for well over a decade, but it's never going to be possible.

You can, of course, bit bang on a floppy drive all day with a MCU or FPGA and do whatever you want, but it'll never be supported in DOS as a real floppy drive. There are plenty of projects that can bit bang old floppy drives, like Kryoflux.

If you want three real floppy drives, you'll need a different motherboard.
 
Thanks, appreciate the explanation regarding PCIe.
I stopped short of looking at the pinout of the connector. But yes it is apparent there is jo hardware support for two drives. Period.

So. Switching the drive and rebooting with adjusted bios is the wsy forward.

At least that works!
 
In hindsight, it is still pretty convenient that this P4P800 board supports an old floppy. It is the only computer I have that can!
 
Even if you had a P4 board with an ISA bus, most use an "ISA bridge" that reserves DMA 2 for onboard floppy, so that won't work either--even if the board vendor claims ISA DMA is supported. My workaday P4 board is an Advantech AIB-742 that has two ISA slots. DMA doesn't work for beans on those--and that's a high-end industrial board. On the other hand, it does support two floppy drives, as do a few Socket 754 AMD boards. That's about as late that I could find mobos with 2 floppy support. Maybe there's an AM2 board out there with 2 floppy support, but I don't recall finding one.

That's one of the reasons that I keep a couple of 440BX P3 boards around. The ISA support there is pretty solid.
 
I went through this last year, and as others mentioned, there is no way.
I added a toggle switch on the rear to flip between the original 3.5 and my new 5.25.
I also added another switch that changes the drive from 360K to 1.2mb by selecting the LD or HD jumper pins. My BIOS has no issues with 360K.
I'd have rather had A: B: but I'm still pleased with how well it turned out.
 
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