I just paid $50 for a 4-drive floppy controller

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I just paid $50 for a 4-drive floppy controller

Postby jmetal88 » Wed Sep 11, 2013 7:37 am

I don't know if I just got frustrated from not finding any deals or what, but I just dropped $50 on this thing:

http://www.ebay.com/itm/300960762471

Basically, I have a computer that I like to call my 'Legacy Interface' build. It has an AMD K6 266Mhz processor, 152MB of RAM, and a motherboard with an odd mix of options (PS/2 or AT keyboard, PS/2 mouse, ISA slots, PCI slots, headers for COM, LPT, USB, etc), but I've been wanting to run three floppy drives in it for a while. I want to be able to access 1.44MB, 1.2MB, and 360kB disks at the same time, and I want to be able to do 360k disks in a native 360k drive. I'd also like the option of adding a 720k drive in the future, should the need arise (though I might need a new case if I did that, as this case only has one externally accessible 3.5" bay). So I dropped $50 on this thing, which came in on Monday.

Yesterday, I got it set up, and while I discovered the built-in BIOS on the thing either doesn't assign drive letters or is overridden by the BIOS on my motherboard, I can access drives on the 'Internal' connector by setting them up in my motherboard BIOS, and on the 'External' connector by using a driver I found online (SDRIVE.SYS, mentioned on this page, worked fine: http://www.seasip.info/VintagePC/floppies.html ). Now I'm just waiting on new floppy cables to get here so I can have all the drives hooked up at once.

While I feel like $50 is a ridiculous price for an old piece of hardware like this, I'm oddly at ease with having paid that price, considering how much trouble it is to switch out two floppy drives on this machine (I had tried installing a physical switch for that purpose and using DRIVER.SYS to create an alias for the switched drive, but it wouldn't work unless I actually rebooted the computer and changed the drive density in the BIOS).

Anyway, I just kind of felt like explaining it to someone, haha. If anyone has anything relevant or related to add, feel free!

EDIT: By the way, I had also tried simply installing another two-drive controller jumpered in 'secondary' mode, but that controller was either incompatible with SDRIVE.SYS or had some conflict with other hardware in my system, as I was never able to access the drives attached to it without setting the jumper back to 'primary' mode and disabling my motherboard's on-board floppy controller.
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Re: I just paid $50 for a 4-drive floppy controller

Postby jmetal88 » Wed Sep 11, 2013 9:04 am

Interesting development: It seems like I can't copy files directly between the third floppy drive and the first or second, or else both drives either report seek errors or general failures. Don't know if that's the fault of the SDRIVE.SYS driver or something odd in the hardware. If anyone knows of any other drivers I could try to add support for third or fourth floppy drives, please let me know! I'll try looking around, and I'll try anything I can find.
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Re: I just paid $50 for a 4-drive floppy controller

Postby jmetal88 » Wed Sep 11, 2013 10:04 am

I'm not where I can get to the computer at the moment, but I think I'm going to try matching the BIOS address on the card to a range my system is able to shadow, then enabling the shadow. Then maybe I can get BIOS access to the drives. If that doesn't work, I'm not sure how the controller having its own BIOS benefits me at all.
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Re: I just paid $50 for a 4-drive floppy controller

Postby jmetal88 » Wed Sep 11, 2013 5:47 pm

Didn't work. :( Seems like if I let my BIOS specify drive letters for the first two drives, they work fine, up until I access one of the SDRIVE-provided drive letters. If I let SDRIVE provide all my drive letters, the drives seem to become inaccessible after a few operations. I wish the option ROM on this thing would just kick in and tell DOS all the drives are there, but either the option ROM is bad, or my motherboard BIOS has decided to ignore it in favor of its own internal settings (and yes, I did disable the internal floppy controller before attempting to use this card).

So, do you guys think I should try an older motherboard? Should I go back from Pentium-type technology to a 486 or 386? Or should the option ROM be working on a system like this? By the way, I had tried using a SCSI controller in this machine a while back, and its option ROM ran just fine, at least for the SCSI part of the controller. I had also tried setting the FDD portion of the controller as my secondary floppy controller, but I couldn't get the system to do anything with that part of the controller.
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Re: I just paid $50 for a 4-drive floppy controller

Postby jmetal88 » Tue Sep 17, 2013 3:01 pm

Okay, I've decided what I'm going to try to do, instead of moving to an older motherboard, is modify the card so that the option ROM can load at a different set of addresses.

Basically, I decided to poke around in DEBUG today to see if I could read the contents of the option ROM while the card was installed in my computer. I could not. It looked to me like some other device was putting data where the option ROM was supposed to be on this card. I tried all three BIOS addresses (CA00, CC00, and CE00) for the card and saw no change in what DEBUG was showing for those addresses (and they were definitely NOT empty). Same data showed in those addresses when the card was completely removed. So, I decided to use DEBUG to poke around at DA00, DC00, and DE00, and all of that address space was completely empty (all FFs), so I figure the card just might work if I fudge with the address decoding circuitry so that the card shows up in the D000 address space rather than the C000 address space.

I basically traced the address decoding for the option ROM to a 74ls138 on the board, where E1 was connected to A16, E2 was connected to A17, and E3 was connected to A15. Since A16 is the line I'm interested in to change the address from the C000 space to the D000 space (1100 to 1101), I figure I'll disconnect the E1 pin on the 74ls138 and just invert the signal going to it. Luckily, it looks like there's a 7404 with a couple of unused gates already on the board, so I think all I'll have to do is cut a trace or lift a pin and solder a couple of jumpers. I'll post back later about how it went (I probably shouldn't start now since I have class in an hour).
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Re: I just paid $50 for a 4-drive floppy controller

Postby jmetal88 » Tue Sep 17, 2013 7:54 pm

That actually worked perfectly. I cut the trace going to pin 4 of the 74LS138, soldered a jumper from a via on one side of the trace to an unused gate on the 7404, and soldered the other pin of the 7404 gate back to the other side of the cut trace. Now my motherboard boots the option ROM and gives me access to all my floppy drives without the need of a driver.
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Re: I just paid $50 for a 4-drive floppy controller

Postby jmetal88 » Wed Sep 25, 2013 6:41 pm

In the interest of having the widest (Microsoft) compatibility I can with this machine, I now have four operating systems installed on it: MS-DOS 6.22, Windows 98 SE, Windows NT 4.0, and Windows 2000. I have my BIOS set to not enumerate my floppy drives so that Windows 98 will still boot. Windows 98 will only see and access the first two drives in this configuration. MS-DOS has to have a DRIVER.SYS line for the third floppy now, but it still assumes the first two are there and gets handed the correct drive type from the BIOS even though the drives are not enumerated. I actually did try adding DRIVER.SYS from DOS 6.22 to the Windows 98 CONFIG.SYS file using SETVER for the third floppy drive, but Windows 98 still refused to boot that way. Windows NT 4.0 and Windows 2000 seem to just probe for floppy drives, ignoring the BIOS drive count, so they see all three of them, although Windows 2000 will not read directly from the 360k drive. Interestingly enough, I can still use disk imaging utilities and get good disk images from the 360k drive in Windows 2000, though. I was tempted to try Windows XP on this machine, but since it just barely meets the minimum requirements, I thought that probably wasn't a good idea, haha.
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Re: I just paid $50 for a 4-drive floppy controller

Postby Trixter » Wed Oct 02, 2013 1:38 pm

jmetal88 wrote:That actually worked perfectly. I cut the trace going to pin 4 of the 74LS138, soldered a jumper from a via on one side of the trace to an unused gate on the 7404, and soldered the other pin of the 7404 gate back to the other side of the cut trace. Now my motherboard boots the option ROM and gives me access to all my floppy drives without the need of a driver.


Quite hard-core!

That's a nice tweener system you have there.
You're all insane and trying to steal my magic bag!
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Re: I just paid $50 for a 4-drive floppy controller

Postby OldComputerGuy » Sun Dec 03, 2017 5:48 pm

I'm trying to find an 8-bit ISA SCSI card and you wouldn't believe some of the prices I am seeing for those.
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Re: I just paid $50 for a 4-drive floppy controller

Postby James » Mon Dec 04, 2017 6:47 am

OldComputerGuy wrote:I'm trying to find an 8-bit ISA SCSI card and you wouldn't believe some of the prices I am seeing for those.


I have an old Seagate ST01, maybe it's an ST02 as it has a floppy interface. I think the Seagate ST01/02 were fairly limited in their device support. I don't have a SCSI drive to fully test it. Make a reasonable offer via PM if interested.

update:
I dug it out. It has firmware version 3.2 so it should work with any SCSI hard drive. Earlier firmware versions were crippled to only work with Seagate SCSI drives. Not good for much beyond hard drives but I have read that people have put modified Future Domain firmware in them.
-PCjr (1989)-DOS 3.3, Racore Drive II, jrIDE-128 MB DOM, jrExcellerator, Tandy Mod, Serial Card, Combo v2, Config Plus, IBM Parallel Port, Megaboard, Xircom PE3-10BT
-PCjr (2001)-DOS 3.3, jrIDE-128 MB DOM, NEC v20, Parallel Port, Comswap, Xircom PE3-10BT
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