Uncreative Labs

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

I posted this over on vintage-computer.com about a week ago, and nobody seemed to pay attention. So, I will repeat it again here. I have found a utility called "2M" that is normally used to increase capacity of floppy disks using special writing techniques...but, it also contains a BIOS extension for XT computers that will let you operate a 1.44 or 1.2meg floppy drive as long as you have a modern floppy controller installed that supports multiple spindle speeds. A controller with a BIOS is not required. You can use a 16-bit multi-io card that works in an 8-bit slot (most of them do).

I've been meaning to try it out, but I'm not able to since I don't have my XT with me. Is there anyone in here that has used this program or who would like to try it and give some feedback?

Joined: 22 Apr 2007 Posts: 264 Location: Ohio/USA

Sorry, don't have an XT.

Joined: 19 Oct 2004 Posts: 138 Location: Lynnwood,WA

I might give it a shot on my XT, since I have the exact setup you describe (dual 1.44M Drives on a 16-bit Multi-I/O, original IBM XT motherboard). Besides, I need to reseat the controller, it's giving me a 601 at bootup, this just might be the right excuse.

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

That's great. Actually, your XT was what inspired me to look for this BIOS overlay in the first place.

Joined: 03 Feb 2006 Posts: 488 Location: pennsylvanai

explain what you mean by a 16 bit i/o on an xt
an at i/o card CAN be used on a xt if it is an 8 bit card
the only 16 biyt card that som,etimes works on a 8 bit 8088 mb is a video card
the bios, unless you have re-written the code and crunched it in the 2764 has no space for a hard drive or a 1.44 or much else besides what's in there.
a hd requires a card with a bios as well as an ega/vga.
since there is no cmos setup( except possibly in some hybrid pc's ) You re severely limited what you can do with an IBM 8088 mb
You can use a 1.44 as a 720k drive.

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

I'll try to clarify things a little bit for you.

What I mean by a "16-bit multi-io" is the IDE controller you typically find in 386 and 486 class machines that also have the floppy controllers, paralllel, serial and game ports built in. These cards are commonly refered to as "multi-io" and usually have a 16-bit ISA card edge connector.

What you may not be aware of is that almost all of these cards can work in an XT's 8-bit slot, but with several limitations. The IDE portion of the card will be non-functional because the card does not have a BIOS, and it also uses the 16-bit portion of the card edge (the one that would hang over the 8-bit slot). The floppy controller however will be functional because it only uses the 8-bit portion of the slot. However, like you said because there is no BIOS it will only support 360k and 720k floppies like a normal XT floppy controller would.

Unlike an XT floppy controller, a 16-bit multi-io card does have the support for other floppy spindle speeds. But, because there is no bios on the card these other spindle speeds are useless. As you said, the reason the 7264 ROM on the XT does not have support for the high density drives is because it is basically full...there is no room for this code.

But the smart guy who wrote the floppy utility "2M" wrote a BIOS overlay for XT computers that can support high density drives through software so long as there is a controller installed that can support the spindle speeds needed by 1.44 and 1.2meg drives.

The overlay is a TSR, and works like an HD overlay or a VESA extension would. It has been possible to support the high density floppies through software on an XT all along, but for some reason nobody bothered to actually write a program that did it until the early 90s when basically nobody was running XTs anymore. It seems that is the reason nobody is really aware of the overlay that comes with "2M". If you want to read about the software, have a look at some documentation I posted over on vintage-computer.com:

http://www.vintage-computer.com/vcforum/showthread.php?t=9661

Joined: 03 Feb 2006 Posts: 488 Location: pennsylvanai

ok I call those 2,3,486 era cards
IDE-i/0 cards used on those pc';s that had nothing but slots for cards and memory & kb connectors.

You did know about vga cards working in an 8 bit slot?

and that early AT's did not support a 720k but the XT did?. there was also a similar problem with early NEC
386? but there was a driver.
the compaticard used a driver and the card had no bios. don't recall if it worked with an xt, but the card was an 8 bit card.

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

Infact, most of the cards currently running in my XT have the 16-bit connectors.

-VGA board
-Sound Card
-IDE/Multi I/O
-Memory Board
-Ethernet Adapter

I've known about the I/O, VGA and ethernet adapters being able to do this trick from the beginning...but the sound card and memory card are pretty new too me. Yes, believe it or not I have a 16-bit 32meg extended/expanded memory card that can work in an XT as a LIM 4.0 board.

I didn't know about early ATs not supporting 720kb drives. I always thought it was the 1.44meg drives that they couldn't support. From what I understand though, it is possible to get the 1.44meg going on any IBM AT using a device driver that comes with DOS.

I haven't used a compaticard, but I do know for a fact that they work in XTs. What I don't understand is why people are willing to pay over $100 for them. What do they do that justifies the cost?

Joined: 27 Jan 2007 Posts: 274 Location: USA

its possible to get alot of 16 bit cards in 8 bit slots, just need to set the irq's to a low number. What model of mem board ya using mr Coward? as for 1.44 support in an XT, i'd just get a floppy controller with onboard bios.(i cant remember if XTs support bios extensions) and as for the compaticard, you can get pentium 2's and 3's for that much! 100$! danm, i probly got over 10000$ worth of parts here!

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

Using a low IRQ is only part of the problem with getting a 16-bit card to work in an 8-bit slot. Most 16-bit cards depend on the 16-bit I/O lines as well unless there is a way to configure it for 8-bit only mode. I would say many of the early 16-bit cards work in 8 bit mode, but I think the later cards depended heavily on pnp and Windows 95 drivers.

The memory board is an Orchid Ramquest 8/16. They are not easy to find. There are no markings on the card that indicate manufacturer or model name. The only way to identify it is by comparing the PCB with the layout on TH99. This is the only 16-bit memory card that I am presently aware of that can work in the 8-bit slot.

Anyway, the BIOS extensions are useful for people who cannot find an 8-bit floppy controller with a BIOS. It's a real pain in the ass. I've been looking locally for years and I've never seen one. I special ordered one from JDR (NIB) a few years back and it didn't work. 2M is great, because it's free and it does the same thing.

I don't know the prices on the early model compaticards, but the compaticard IV in particular is the one that regularly goes for over $100. Do you have a lot of these or something?

Joined: 27 Jan 2007 Posts: 274 Location: USA

nope, but i got a few 8bit high density floppy controllers with built in bios, but there under 5 feet of other isa cards.

Joined: 03 Feb 2006 Posts: 488 Location: pennsylvanai

THE ONLY xt floppy card i didn't like was the dtk
it would not properly format all floppies.
I returned it.
other cards never gave me a problem.

yes the lack of bios extensions was only the early IBM PC.
for a hd conmtroller to work it had to see the bios on the hd card.

Joined: 19 Apr 2006 Posts: 261 Location: WisConSin

Something I've often wondered is why a simple driver could not be made to allow for 1.44mb access.

I already have an XT with a 16bit IDE-multi I/O card that works OK without IDE enabled.

So if that card was designed for 2.88mb operation why couldn't a TSR be made to overcome the bios aversion to 1.44mb floppies?

Even the IDE can be pinged using low level maxtor format software but it gives corrupt ID's for the drives.

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

Ah, but there was a program made...and it is called "2M V3.0". Download it and give it a shot.

Joined: 19 Apr 2006 Posts: 261 Location: WisConSin

Hmm, I will have to try the 2m utility.

386er wrote:

its possible to get alot of 16 bit cards in 8 bit slots, just need to set the irq's to a low number. What model of mem board ya using mr Coward? as for 1.44 support in an XT, i'd just get a floppy controller with onboard bios.(i cant remember if XTs support bios extensions) and as for the compaticard, you can get pentium 2's and 3's for that much! 100$! danm, i probly got over 10000$ worth of parts here!

Um no, although sort of. I have an IDE card in that category (AKA wired to IRQ 7) what happens when I ping the drive is I get lots of garbage, the IDE utilities see something there but because half the data is lost all I get is garbage for parameters.

I have a feeling though that if 8 bits are getting through (as I can see something there) it may be possible to mod a 16bit IDE controller to control 8bit IDE drives but they are also very rare, very small and not really better than MFM.

Its too bad modern IDE drives can't be multiplexed in some simple way to interface to 8 bit IDE which is so much simpler to deal with on an xt.