Full Fat DooM, on an XT?!

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Earlier in the week I promised you all a video about how I was going to stick the IBM Blue Lightning 3 chip into my XT, via the Intel Inboard. Well, due to a shortage of EPROM chips and the lack of an EPROM eraser, that hasn't happened quite yet. AliExpress to the rescue! (So I'll make that video in around 9 weeks time - heh!).

But never fear, because I have something possibly as good! A video on an attempt at possibly a world first: Run DooM on an PC/XT... which admittedly has an Intel Inboard card in it to make it go faster...and access 4MB RAM..and do 32 bit transfer...and do protected mode... but all that aside, this is an attempt at getting DooM working on that special machine. Until now, as far as I know, nobody has gotten it to work, due to the fact that the PC/XT keyboard works differently to how the AT keyboard works. If you look over here at the very excellent Jim Leonard's (trixter) blog, you'll see that many years ago, he found that whilst the AT (and all modern PCs) scan 60h for the keyboard scancode, the XT keyboard also needs to scan bit 7 of port 61h (if I read trixter's blog correctly).

In my last video, at the end I showed DooM running, but not accepting keyboard input when the main game loop starts. I looked on vcfed and true enough, it looked like nobody else had gotten (proper) DooM working with the keyboard on an XT with an Intel Inboard. Fast forward a few days after the release of that last video, and someone by the name of FrenkelS on BlueSky posted :
"Here's a version of @viti95.bsky.social's FastDoom with keyboard code that should work on an XT."

The github link: https://github.com/FrenkelS/FastDoom/.... As of 20th August 2025, I now am happy to report that FrenkelS' code mod has been added into the main branch of viti95's FastDoom. You can use it with the cmdline option -xt :)

So, how well does it run, I hear you ask?! Well, for that, you'll just have to check out the video, but remember, this is all pre Blue-lightning CPU upgrade, so hopefully, the performance will be even better when I release my blue-lightning CPU demo!
00:00 - Introduction
01:35 - DooM won't work on an XT (keyboard)
04:25 - The supposed fix
06:22 - Starting up DooM on the XT
09:03 - FastDoom graphics settings
09:26 - Running full detail
13:44 - Quality settings
15:22 - CGA Doom
15:49 - EGA Doom
17:07 - Textmode Doom
17:53 - Conclusion