Hello Everyone.
I've did some research and I can say that the floppy bios from Sergey Kiselev is I would say in a halfway.
I'm playing now with a newly build old computer and I've decided to assemble something with multiple floppies and multiple OSes.
And yeah - I've spend almost a month on understanding what's wrong with my setpu.

First of all - main BIOS. I've tried ATC-1020, Biostar M5ATA, and Chicony CH-471B.
- You can forget about using second controller on ISA to get 4 floppy setup. You have to disable embedded controller, use quad floppy card, or two double floppy with configurable I/O. Seemingly everything works with embedded controller but 5,25 can't properly read the files. Maybe it's the matter of jumper settings on my 5,25's but those were perfectly working on build in BIOS, but fail on SK BIOS.
- You can forget of using 4 floppy setup with SK BIOS with to new main BIOS. Every time when I was burning BIOS (4.51) newer than 1997 the motor on signal was saying bye! I have no idea if this is related to different int 13h handling or simply with signal routing pattern in newer BIOSes but it always ended up like this.
- Windows 98 - forget it - it can't handle 4 floppies. You will get protection error.
- Windows 95 - if you have correct BIOS and correct cards and correct setting all you have to do is to disable standard floppy controller in device manager. FDDs are still working (all 4) and you won't get protection error anymore.
- If you have bad luck and this doesn't work then you have to set up floppy A in BIOS (keeping embedded controller disabled).
- Forget about using Sergey's BIOS with XT_IDE (IDE_386) - IDE_386's way of handling INT 13h and swapping FDDs will drive you mad . On newer BIOSes you can integrate Sergey's or XT_IDE's or both in main BIOS but then forget about using Windows 9x. On older BIOSes without fully implemented handling of ISA or PCI roms this won't work. You can successfully add those modules to the main BIOS using cbrom or awbedit but those won't be loaded into memory.

Couple words about sdrive and other drivers. The most reliable is the driver from DOS 6.22 - it's just working. Others (DC2, Sdrive, Wonder34, DOSFDRV) - if you have proper hardware can work, but many kontroler just don't want to communicate with them.

Of course still there is a lot of fun checking which particular EPROM of with particular capacity will work in ISA card and which in PCI card and so on, so forth.
Unfortunately my understanding of PC architecture is very general so I couldn't debug it properly.
All I could do was to fail and learn.

Best regards!

After some additional insight I've discovered that there is an update for IOS.VXD for Windows 95 that make it works with 4 floppies.

Hello!
Does anyone have a schematic diagram of this adapter?
https://texelec.com/product/8-inch-floppy-adapter/

disaster wrote on 2024-01-04, 21:24:

After some additional insight I've discovered that there is an update for IOS.VXD for Windows 95 that make it works with 4 floppies.

Can you provide any details on how you got this to work?

I've been piecing together a patch for Win95 that fixes the floppy issue and also supports fast CPUs. I based my patch heavily on this:
https://archive.org/details/fix-95-cpu-v3-final

I added-in the special version of IOS.VXD you had provided. Please see my attached disk image (HxC).

-Brian

I've made some breakthroughs. In fact, I now have a working proof of concept with Windows 98!

Currently, I'm experimenting with beta OS builds. However, the drives fully work. My plan is to try GA builds of Windows 98 next...

-Brian

I got this to work with the GA version of Windows 98 SE.

Here are the steps I took:
1.) Disable floppy drives 3 & 4 in the BIOS
2.) Install Windows 98
3.) Remove the Floppy Controller in Device Manager
4.) Boot from another device (i.e.: floppy or USB)
5.) Copy IOS.VXD, HSFLOP.PDR and ESDI_506.PDR to their corresponding locations
6.) Enable floppy drives 3 & 4 in the BIOS

-Brian

[REMOVED FILE]

what the hell is the "GA" version

also why did you have to mess with ESDI506.PDR?

This is great news for frustrated quadflop owners such as myself.
I currently have DOS/WFW 3.11 (ABDE)..and Win98se (AB)on 2 CF cards....and a modified reset switch to disable the quadflop bios when needed..
Hopefully your patch works for me.
cheers..
VS

maxtherabbit wrote on 2025-11-26, 14:20:

what the hell is the "GA" version

GA = General Availability. Normal retail version. I was making the distinction from the beta versions I was testing.

maxtherabbit wrote on 2025-11-26, 14:20:

also why did you have to mess with ESDI506.PDR?

This was necessary to keep files version-level. While unrelated to floppy use, it has a dependency on IOS.VXD

-Brian

Vipersan wrote on 2025-11-26, 16:22:

This is great news for frustrated quadflop owners such as myself. I currently have DOS/WFW 3.11 (ABDE)..and Win98se (AB)on 2 CF […]
Show full quote

This is great news for frustrated quadflop owners such as myself.
I currently have DOS/WFW 3.11 (ABDE)..and Win98se (AB)on 2 CF cards....and a modified reset switch to disable the quadflop bios when needed..
Hopefully your patch works for me.
cheers..
VS

I do want to point out that I have the Monster FDC, which is very similar to the Quad Flop. However, my patch should work with your controller.

-Brian

Well I took a differant aproach...but for me it did not appear to work ??
Disk designation is set to none in the bios..so nothing defined for A or B.
the motherboards on board floppy controller disabled.
Since my OS in this case Win98se is on a CF card so pulled this and mounted in my main PC (adapter)
Navigated to SYSTEM >IOSUBSYS...and deleted HSFLOP.PDR and replaced with the one from your patch Brian.
ESDI_506.PDR did not exist .....but I copied yours in anyway.
then navigated to VMM32.....found ios.vxd ...deleted this also and replaced with your version.
Turned on the quadflop bios...re-fitted the modified CF card and booted up Win98.
The boot completed without protection error.
Feeling pleased I opened up windows explorer..
I was greeted with 4 floppy drives in the order I set them in the quadflop bios.
A B D E - 1.44mb 1.2mb 720k and 360k
Curiously the C drive/CF card showed up twice ?? at C: and F:
I tried to read floppy disks in all 4 drives...no write tests yet.
....but the appropriate LED lit ..and no data returned...?
Not even sure if the motors were spinning...just hung for over a minute at least ...with the selected LED lit...and had to remove the disk...and wait an age for win98se to catch up so I could exit the drive.
Is the drive order pre set in the replacement drivers...or should this reflect the quadflop bios set order ?
Sooo near yet so far.
VS

I wasn't having much luck with the FDC BIOS. Looks like you got further than I did with floppy drive detection, using the FDC's BIOS

I went the other direction. Instead, I found a way to get my motherboard BIOS to support 4 floppy drives. Apparently, MRBIOS does well with this. Not sure what motherboard you have. But, this thread was helpful:
Intel Zappa MB /w. MR-BIOS ==> No CD-ROM

My Monster FDC has 2 controllers (supports up to 8 drives). I disabled the primary FDC on my card. For drives 1 & 2, I'm using my motherboard's FDC. And for drives 3 & 4, I'm using the Monster FDC.

I'm curious to hear more about what you tried. Are you using any DOS drivers, like SDRIVE.SYS? I would love to get this to work with another motherboard that doesn't support 4 floppy drives.

-Brian

Here are the jumper settings for my FDC. This uses the same BIOS (currently disabled) as the Quad Flop. So, it should be largely compatible with your setup.

-Brian

I'm not using DOS drivers Brian ...ie SDRIVE.SYS ....The Quadflops bios is 100% compatible with DOS ...and win 3.11..thus I can use IMD/4
....and just read/write any to any of my drives with DOS commands.
The motherboard is a Biostar MB-8500TTD flashed with Jan Steunebrink BIOS patch for Cyrix 4x, AMD K6-2, AMD K6-2+, AMD K6-III, AMD K6-III+
It would have been nice to get all 4 floppy drives to fully function in 98se...but if that doesnt happen I can use the earlier windows WFW 3.11....and DOS of course so all is not lost.
I shall keep an eye on your progress with this problem.
In the meantime I have a solution by enabling the quadflop bios and swapping out the CF card.
rgds
VS

My motherboard has the same chipset as yours. Definitely check out the link discussing MRBIOS. In particular, the last post will be of interest...

-Brian

Vipersan wrote on 2025-11-26, 22:42:

I'm not using DOS drivers Brian ...ie SDRIVE.SYS ....The Quadflops bios is 100% compatible with DOS ...and win 3.11..thus I can […]
Show full quote

I'm not using DOS drivers Brian ...ie SDRIVE.SYS ....The Quadflops bios is 100% compatible with DOS ...and win 3.11..thus I can use IMD/4
....and just read/write any to any of my drives with DOS commands.
The motherboard is a Biostar MB-8500TTD flashed with Jan Steunebrink BIOS patch for Cyrix 4x, AMD K6-2, AMD K6-2+, AMD K6-III, AMD K6-III+
It would have been nice to get all 4 floppy drives to fully function in 98se...but if that doesnt happen I can use the earlier windows WFW 3.11....and DOS of course so all is not lost.
I shall keep an eye on your progress with this problem.
In the meantime I have a solution by enabling the quadflop bios and swapping out the CF card.
rgds
VS

I couldn't find an MRBIOS BIOS for your specific motherboard. But, this one looked to be a close match.

I wouldn't test, unless you have an EEPROM programmer... or some other way of flashing the BIOS, if things go awry... I take no responsibility...

-Brian

My BIOS Chip is a macronix 28f1000ppc-12c4
My TL866 does list a macronix part 28F1000P without the bit at the end. (PC-12C4)
Maybe I could try obtaining one to flash with your suggested bios Brian.
That way I dont have to gamble with my working bios ?
Ive grabbed a copy anyhoo.
Now to find a suitable chip 🤣

After much searching I found some for sale in Poland pack of 3 used MX28F1000PC-12 which hopefully I can use.
The shipping cost was twice the price of the chips but still.
Not too bad at £12 in total ...but I guess I'm in for a lengthy wait.
Doh !!

I've been doing more testing and I have an update.

While 4 floppy drive support is working in Win98SE (Retail), something with the use of CDROM broke.

I tried Win98FE (Retail) and I'm not having much success with installation. As far as I can tell, the IDE controller driver does not like this machine. I didn't even get the chance to try my patch. So, it's hard to test the CDROM functionality with this OS.

Ironically, Win98FE (beta 1900) installs just fine. And that's a very late RC4 build. So, not sure what's different there. However, I'm getting the same CDROM errant behavior exhibited in Win98SE, using my patch.

Finally, everything works just fine in Win98FE (beta 1593). CDROM works great. This demonstrates that there should be a combination of file patches that will ultimately work for Win98FE (Retail)... and possibly also Win98SE.

I'm going to continue my testing and find the lastest beta build of Win98FE works for both floppy and CDROM. I have around 40 beta builds, so this will take a little time.

If anyone here has a deeper understanding of how CDROM 32-bit mode operates in Win98, I'd appreciate any insights. In particular, I'd be interested in learning more about which system files (and dependencies) are in play.

-Brian

Thanx for the update Brian...I shall be watching your progress with interest.
Sadly I'm not smart enough to be much help other than as a tester.
Good luck mate I'm sure you'll solve this conundrum eventually 😉