FDC Emulator: MFM Data Generation & WinSTon: IPF Testing

28 November 2004

Disk sector image to MFM Data conversion

Since the IPF support is pretty much working, we spent a while working on the data conversion routine, which is used to load sector based images (for exmaple: .ST files) and convert them to MFM at runtime. We took the decision to make the tracks appear as if they were actually formatted by TOS. We wondered if there was any TOS versions where you could select the number of sectors per track. Although a quick search revealed that there did not appear to be any options like that in the versions of TOS available to us, it seems that there were other tools that could be used to format disks with a selectable number of sectors per track.

And after a fair amount of effort, the disk converter works! Disks with 9 or 10 blocks should be fine. We got the TOS default format by observing the FDC track write commands used during formatting. The 11 block format was ripped from the track write command of a program called “andy copy”, and still needs to be verified.

Emulator Testing

Now that we have the data conversion running, we can easily load the legacy files that were previously causing trouble and test the status of our modified WinSTon. The games “New Zealand Story” and “Turrican” that use an 11 block-format (and possibly many others) work now. However Turbo Outrun is broken. This might be something bad with the generated 11 sector format or a bug in the FDC emulation.

Results of the game testing reveals:

  • Afterburner - Now works
  • Batman The Movie - Still not working. Could be a bad image or an emulation bug.
  • Test Drive - Emulator crashes, seems a CPU core problem.

IPF Testing

Here you can see a screenshot of Flimbo’s Quest at Level 2 running in our modified WinSTon using a test IPF image. Getting to Level 2 is important because a strong protection check is only done after completing levels. This is a good trick to fool pirates into thinking their copy of the game works, and it does... Until level 2.

If you are familiar with the original WinSTon emulator, you might notice the toolbar is unfamiliar. We replaced it.1) We decided we might as well improve the general look of the emulator while we were developing our cycle-exact FDC system. The previous toolbar made the emulator look rather dated.

1) You can click the screenshot to get a full-size version.