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Multi-floppy Bios Extension or DOS Driver? Which is better?

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    Multi-floppy Bios Extension or DOS Driver? Which is better?

    I've recently put together a multi-floppy 386. I'm currently using the SUNIX sdrive.sys driver and have successfully been able to get 8 floppy drives to work simultaneously. Here are some pictures:

    I was thinking about getting a lo-tech ISA ROM extension card and running Skiselev's multi-BIOS extension instead of using the driver. What are the benefits of using a bios extension over a driver?

    I built the computer with the thought of just using it as a dedicated disk imaging system. Would the BIOS extension have benefits the software does not have?

    I don't think you really mean "simultaneously". I think you mean that a program can host access to one of 8 drives at a time. "Simultaneously" would imply mult-threading, with each thread accessing a drive.

    Again, nothing new--I've had a system with 6 drives running since 1992; a customer used 12 drives.

    And they were running a program that allowed for simultaneous access to three drives at a time. That's pretty much the limit--you have 3 8 bit DMA channels available. Even there, it strains the ISA bus a bit.
    Last edited by Chuck(G); March 23, 2021, 10:59 AM.


      That is an awesome system. One can never have too many floppy drives

      So, I take it, there are two floppy controllers each of which support 4 drives each?


        On mine, 3 controllers, one per IRQ/DMA/Port, connected to 2 drives. Given that they're all Compaticard IVs, I could have 12 drives, like my customer. If you didn't need simultaneous data transfer, you could put in 4 compaticard for 16 drives.

        But what would be the point? Floppies are dead technology. For a time, I played with the idea of making a 4 controller ISA card and even have a tube of WD37C65s that have never been used. At some point, however, if duplication is your goal, it was more cost effective to simply buy or lease a Formaster, with its high-speed drives and auto-feeder.

        Since I still have most of a carton of FD505s, I briefly toyed with the idea of a 12-drive system in a single box.

        Add a couple of Backpack floppies and you could extend that a bit more.


          Simultaneously was clearly the wrong word. I was just trying to indicate that both floppy controllers were working.


            Originally posted by SomeGuy View Post
            That is an awesome system. One can never have too many floppy drives

            So, I take it, there are two floppy controllers each of which support 4 drives each?
            Thanks! It's been a fun project. Yes, The primary floppy is an Everex 8120A. This is a good solid 4 floppy/IDE card that I've had for years. I'm using the IDE interface on that card to boot the computer with a CF card. This card does not allow me to assign a DMA/IRQ to the card, but it's a good card.

            The second controller is an Exabyte Tape Backup controller. To get that card to work, I had to modify the card a bit. I replaced the 48MHZ crystal with a 24MHZ one. I also put a new header on the card for the 3rd and 4th floppies. This card works really well with those modifications and does allow you to jumper select the IO address, IRQ and DMA. It was not my idea to modify the card. I found this video on Youtube by user Blazil where his 8 floppy system uses two of these cards.


            I found the one I use on ebay recently in a lot purchase of ISA cards. I think I got a good deal. They have them on PriceBlaze if you're willing to spend extra money.

            I went ahead and ordered a ROM card to try the multi-floppy extension. I'll compare the two and see which one seems best.