I added an XTIDE card and programmed it with the large XT BIOS. The behaviour was a little unexpected, probably because the floppy disk implementation is not 100% compatible with an IBM PC. The Universal BIOS has trouble associating the drives with drive letters often confusing the flash disk with the third floppy. Selecting floppy drives by letter at startup also resulted in boot failures.
Curiously, invoking the menu and then using the arrow keys to select the boot drive from that menu worked fine. Perhaps the relevant data is reread at that point; only a XTIDE Universal BIOS expert would know.
But, fortunately, the Universal BIOS will allow the system to boot from any of the floppy drives – as long as it is selected from the Universal BIOS menu.
MS-DOS 3.2 is limited to 32MB partitions, which is a little tight. This is probably not a major issue for this machine which is likely to have only occasional use. I could not get the card to boot, but it worked fine otherwise.
I set up a second CF card with DOS 5.0. I was able to make this one bootable and i could set up a full 512kB partition. There is no specific version of MS-DOS 5.0 for the One, so there are a few places where IBM incompatibility rears its head. Firstly the battery backed real time clock does not work, and secondly MS-DOS 5 seems to politely ignore the incompatible serial ports.
With XTIDE and Universal BIOS there are a variety of outcomes depending on the operating system and the boot drive:
| OS | Boot Drive | Notes |
| MS-DOS 2.1 | A 3.5″ Front Internal | Boots. Can access floppy drives A(front), B(rear), C(5.25″). Appears to not have hard disk support. Was unsuccessful formatting C. |
| MS-DOS 2.1 | B 3.5″ Rear Internal | Boots. Can access floppy drives A(rear), B(front), C(5.25″). Appears to not have hard disk support. Was unsuccessful formatting C. |
| MS-DOS 2.1 | C 5.25″ External | Not attempted. |
| MS-DOS 2.1 | CF Card | Appears to not have hard disk support. |
| MS-DOS 3.2 | A 3.5″ Front Internal | Boots. Can access CF card with 32MB disk as D. Can access floppy drives A(front), B(rear), C(5.25″). Can write to rear drive but not format. Can format 5.25″ drive and write. |
| MS-DOS 3.2 | B 3.5″ Rear Internal | Boots. Can access CF card with 32MB disk as D. Can access floppy drives A(rear), B(front), C(5.25″). Can write to rear drive but not format. Can format 5.25″ drive and write. |
| MS-DOS 3.2 | C 5.25″ External | Boots. Can access CF card with 32MB disk as C. Can access floppy drives A (5.25″), B(front), D(rear). Can write to rear drive but not format. Can format 5.25″ drive and write. |
| MS-DOS 3.2 | CF Card | Does not boot. Have to boot from floppy. Then card can be accessed. See above. |
| MS-DOS 5 | A 3.5″ Front Internal | Boots. Can access CF card with 512MB disk as C. Can access floppy drives A(front), B(rear), D(5.25″). Can write to rear drive but not format. Can format 5.25″ drive and write. |
| MS-DOS 5 | B 3.5″ Rear Internal | Boots. Can access CF card with 512MB disk as C. Can access floppy drives A(rear), B(front), D(5.25″). Can format 5.25″ drive and write. |
| MS-DOS 5 | C 5.25″ External | Boots. Can access CF card with 512MB disk as C. Can access floppy drives A(5.25″), B(rear), C(front). Can format 5.25″ drive and write. |
| MS-DOS 5 | CF Card | Boots. Can access CF card with 32MB disk as C. Can access floppy drives A(front), B(rear), D(5.25″). Can format 5.25″ drive and write. |
The rear drive seems to have a strange fault that allows writes but prevents format. May just be in the detail of the format program. The drive system is not 100% IBM compatible.
When formatting DOS 5 seems to treat all drives as 360kB by default. It may be possible to use format options to override but i found it very reluctant. Use driver.sys in config.sys to create new drives E and F that are 720k. Required on any DOS 5 boot disk.
All up, it’s a pretty complex picture!
My XTIDE card does not have a rear facing slot to allow the CF cards to be easily changed. Often, i have to make do with what we can economically get in Australia. XTIDE does support two cards though, and there is plenty of space in the hard drive bay to house them. MS-DOS 3.2 does not see the 32MB drive, but DOS 5 sees both.
With a large hard disk, the first directory listing can take a long time. This is particularly noticeable on my PCs that have 2GB partitions. This effect seems accentuated on this machine and is very noticeable with the 512MB partition. I suspect that the bandwidth using the expansion unit is much lower than with the built-in expansion bus of the IBM PC and similar machines. Nevertheless, it is quite useable.