FM Towns CD Structure

Today I had one of those stray thoughts that turned into an exercise that consumed my entire day.

I've always been fascinated with the FM Towns PCs. I own a 20F, which, except for the fact that the lcd panel (cd access light and volume meter) is dead, it's in pretty good working order.

One of the games I have for it is Wing Commander II. I upgraded the RAM and hunted down a hard drive just to be able to install and play it. While I read and understand enough Japanese to muddle through, I'm nowhere near fluent enough to really get the experience the way it was intended. I came across a GOG add showing Wing Commander I and II on sale for something ridiculous like $3, and that got me thinking about playing the copy I already own. I thought since the FM Towns is DOS-Based, I bet the game layout isn't all that different. If I could identify the language and speech files and replace them with English versions from the DOS edition, I might be able to play the game in English on my Towns.

As it turns out, I didn't even have to hunt down the English language files. They're all present in the Japanese installer. The original voice and scenario files have file extensions like *.S00,*.S01, etc... The Japanese versions of these files have *.J00 etc... After installing the game in UNZ - including remembering how to format a stupid hard drive from within Towns OS - I loaded up a DOS prompt, copied the English versions of a couple of the files over top of the Japanese versions, fired up the game, and Bang! English. Well, there are about 50 or so files altogether that have to be renamed, which is a major time consuming PITA, so I decided that it would be much better to rip the CD and write a new one with the files pre-renamed. (It would probably be more elegant to alter the executable to just read the English files instead, but I really didn't feel like hex hunting today.)

The original disc layout looks similar to Sega CD discs - Track 01 is Mode 1/2048 ISO 9660, and tracks 2 through 46 are PCM audio. I haven't done any ISO jiggering for a while and it seems most of the tools I used to use for this kind of thing won't run in Windows 7. Best I could manage was ripping the individual tracks out with an old version of ISO Buster. From there I extracted the data track, did all of my file renaming, then wrote the resultant directory back to an ISO file - being careful to match it as closely as possible to the mode of the original file. I know that FM Towns didn't actually use the first 16 sectors for booting, so I didn't bother trying to replicate that. Obviously the size of the data track changed, so I used IMGBURN to generate a new cue sheet, and wrote it all back down to an image file. Unfortunately UNZ wouldn't boot from the image file. I did a straight-up rip of the original to make sure it wasn't something wrong with the drive emulation - and the straight-up copy worked fine. Once booted I switched back to my altered CD image and the Towns could read it just fine, but it wasn't firing off whatever automagical thing it did with the original where it just presented a single icon a-la autoexec.bat instead of showing the drive contents.

After trying a couple more times to produce an image the system would boot from, I got goofy and used the untouched image to fire up the installer, then swapped discs just before hitting the install button. The installer copied the files from my altered disc to the HDD and when I fired up the game it was in English.

I reproduced these steps on my 20F and it worked pretty much the exact same way (albiet way slower, lol), so I can play the game in English on my Towns.

But it still nags at me a little that I wasn't able to produce a working CD with my altered data track. I remember way back when we were all just starting to discover how to rip PCE CDs, those things were extremely sensitive to things like LBA alignment - evidently preferring to access the tracks by LBA rather than use the TOC, but I have a hard time believing the Towns would be that way. Does anybody have any more information on the idiosyncrasies of the FM Towns CD format - something that might explain where I went wrong?

Thanks for reading.

 

There is no "FM Towns CD format". It's ordinary ISO9660. What you are messing with is the data/file structure of Wing Commander II. I doubt it's a direct port, so you most likely can not just swap files from some other version.