Getting XTIDE Working on the Amstrad PC1640

Amstrad, DOS, PC, Retrocomputing, XTIDE

Getting reliable, modern storage into an Amstrad PC1640 means a Lo-tech XT-CF adapter running XTIDE Universal BIOS — it lets a CompactFlash card stand in for a hard drive. I bought the TexElec version, which comes with the BIOS pre-installed, so the hardware side was the easy part. Getting it to actually boot was a different story.

What didn’t work

Worth documenting the failed attempts here, because each one narrows down where the real problem actually is.

Attempt 1: wrote a bootable OS image to a 64MB CF card using Rufus. Booting from it just hung at Booting C>>C.

Attempt 2: booted the PC from a DOS 3.3 floppy instead, then used fdisk to partition the CF card and format /s to copy the system files across. DOS 3.3’s filesystem limitations meant capping the number of cylinders low (200). This got the drive mounted and usable — but only while booted from floppy. Booting from the CF card directly still failed with the same Booting C>>C error.

Attempt 3: switched to serdrive, which mounts a floppy image over a serial port (COM1) instead of a physical disk — useful since the PC1640 doesn’t have a lot of good options for getting boot media onto it otherwise. It’s not included in the latest XTIDE Universal BIOS binaries, so I had to track down an older version that still had it.

Booted an MS-DOS 6.2 disk over serdrive and ran fdisk /mbr, which did fix the Booting C>>C hang — progress — but immediately hit a new error: Boot sector not found.

Attempt 4: tried a larger 16GB CF card. Booted DOS 6.22 over serdrive, used fdisk to create a 2GB primary partition — that part worked fine. But DOS 6.22’s format failed to actually format the partition or copy the system files. Formatting the same partition from Windows 10 worked, but produced a partition that wasn’t bootable at all.

What finally worked

  1. Install the XT-IDE card in the PC1640.
  2. Download serdrive.
  3. Connect a USB-to-serial-port cable, with a null modem adapter in between.
  4. Get a DOS 5 boot floppy image.
  5. Boot from serdrive.
  6. Run FDISK /mbr — proactively clears out any stale master boot record/boot sector state on the CF card before doing anything else.
  7. Run FDISK to partition the CF card.
  8. Run Format c: /u /s.
  9. Reboot and confirm everything comes up cleanly.

That’s it — the DOS 5 + serdrive + fdisk /mbr-first combination was the piece that made everything else fall into place, after DOS 3.3 and 6.22 both hit their own separate walls.

Other things worth knowing

  • Hotkeys: Alt searches COM ports for mounted serial drives while in the BIOS/boot menu.
  • You can’t run the original MFM drive and XTIDE at the same time. The XTIDE BIOS simply doesn’t load if the MFM controller card is also connected — seems to come down to which card sits in the first ISA slot. Only one can be active.
  • Not yet tried: using the original Amstrad installation images instead of a generic DOS install — might sidestep some of this entirely, but hasn’t been tested.

If you’re doing this yourself, the short version is: skip straight to the “what finally worked” recipe above and save yourself the DOS-version trial and error.

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