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There's plenty of YouTube videos about it, search for something like "commander keen cga" or "xt games cga" to get a feel for what it usually looked like. I'm

There's plenty of YouTube videos about it, search for something like "commander keen cga" or "xt games cga" to get a feel for what it usually looked like. I'm a little older and spent a nontrivial amount of time on CGA, so this demo absolutely blew my mind.

jchw 4y ago
I am trying to be a bit humble since my experience is definitely limited, but to be clear, I do have some experience with an XT clone at least. Still, I haven't written very much code targeting an XT machine, and especially, I have never mucked with CGA beyond BIOS routines. I've got to imagine that even Commander Keen had to be doing some pretty hot tricks, even though the only novel technique I'm aware of is the EGA adaptive tile refresh one, not anything CGA. Of course, it's never too late to write some wares for XT... I'd prefer to get an actual XT for that, though. I'd fear that if I only ever tested on emulators or clone machines, I would end up writing code that doesn't work on any actual XT :)
- Scali 4y ago
  That is known to happen, yes: https://scalibq.wordpress.com/2015/08/09/fixing-genesis-projects-gp-01/ https://scalibq.wordpress.com/2015/08/09/fixing-genesis-proj...
  - jchw 4y ago
    Is dosbox being used as an example, or was that actually the emulator? I find this intriguing. I would've assumed PCem or MESS was a better choice for writing a demo for something like an XT computer. Dosbox is useful but it definitely hits me as something that is emulating a software library per se, and only the hardware as an accident of that, a valid approach that is a lot less useful for programmers working under it...
    - ajenner 4y ago
      I used the DOSBox debugger to debug several of the effects during the making of Area 5150, but other than that I used real hardware. 86Box is probably the most accurate one at the moment but still isn't accurate enough to run the entire demo correctly.
    - Scali 4y ago
      Given that the demo targets AT-class hardware, it is unlikely that something like PCem or MESS was used, because in those cases you'd actually have to select an AT-configuration to make it work, instead of an XT-configuration. DOSBox does not have this option, it always emulates AT-class hardware, in which case this demo 'just works'.

jchw 4y ago

I am trying to be a bit humble since my experience is definitely limited, but to be clear, I do have some experience with an XT clone at least. Still, I haven't written very much code targeting an XT machine, and especially, I have never mucked with CGA beyond BIOS routines. I've got to imagine that even Commander Keen had to be doing some pretty hot tricks, even though the only novel technique I'm aware of is the EGA adaptive tile refresh one, not anything CGA. Of course, it's never too late to write some wares for XT... I'd prefer to get an actual XT for that, though. I'd fear that if I only ever tested on emulators or clone machines, I would end up writing code that doesn't work on any actual XT :)

Scali 4y ago
That is known to happen, yes: https://scalibq.wordpress.com/2015/08/09/fixing-genesis-projects-gp-01/ https://scalibq.wordpress.com/2015/08/09/fixing-genesis-proj...
- jchw 4y ago
  Is dosbox being used as an example, or was that actually the emulator? I find this intriguing. I would've assumed PCem or MESS was a better choice for writing a demo for something like an XT computer. Dosbox is useful but it definitely hits me as something that is emulating a software library per se, and only the hardware as an accident of that, a valid approach that is a lot less useful for programmers working under it...
  - ajenner 4y ago
    I used the DOSBox debugger to debug several of the effects during the making of Area 5150, but other than that I used real hardware. 86Box is probably the most accurate one at the moment but still isn't accurate enough to run the entire demo correctly.
  - Scali 4y ago
    Given that the demo targets AT-class hardware, it is unlikely that something like PCem or MESS was used, because in those cases you'd actually have to select an AT-configuration to make it work, instead of an XT-configuration. DOSBox does not have this option, it always emulates AT-class hardware, in which case this demo 'just works'.