Why some games don't work on Mindset

[falter]

This is purely for my own curiosity and understanding. I decided to try testing the limits of my Mindset to see just how compatible or not it was. When 8 Bit Guy reviewed it he suggested pretty much all graphical games would not work. He only tested his own though.

I've now tried about 15 games. I tried to limit it to games that were out in 84 or earlier when the Mindset came out, since those would have been the ones engineers were aware of. I thought that earlier, simpler games would have the best chance of running.

I expected that games would either load up and work or not load up at all. I got a few of those. Games like Wheel of Fortune and Mindshadow worked no problem - they loaded up in 4 color CGA so Mindset did provide some graphics compatibility. Games like Flight Simulator didn't. However there were a bunch that were sort of in between. Test drive fired up.. the intro froze, but then it went to car selection. But when you selected a car, it froze. Earlier CGA games like Shamus loaded to a title screen but died on trying to proceed.

I tried to find a pattern but it didn't make sense. At first I thought maybe sound, but Wheel and Lode Runner have sound and work fine. Graphics aren't a problem since the Mindset clearly can emulate 4 color CGA. Memory doesn't seem to be an issue. I feel like a hint came when King's Quest started up, got to the title screen and froze, but weirdly the text entry area changed from the usual 40 columnish mode KQ normally uses to 80 column. Side note: I also tried Adventures in Serenia. But that one was weird.. I could run it from hard disk on my P3, but the second I copied to a known good floppy and ran it.. it froze. On the Mindset it kept saying Sector Not Found, but on the P3 it just went blank screen. I even copied all the files back from the disk to hard disk in a different directory and it ran fine... weird.

Yeah I'm just curious.. what other resources would a CGA era game call upon in such a way that it might start up partially but then freeze when you actually try to play? I'm wondering if it'd theoretically be possible to narrow down the issue and patch games or such to make them work. I'm not actually planning on doing that.. I don't have the skills to do it.. I just find it interesting how some games hit that middle failure mode and seem to be functional up until you attempt to play.

 

[Plasma]

Probably graphics and/or keyboard related. See page 28. For example, if a program hooks int 9, it's going to wait forever for a keypress that never happens.

 

[falter]

I wondered about keyboard.. but it does respond to that in many cases. Test drive will sit there at the select car screen.. its only when you hit enter to carry on that it locks up.

 

[Eudimorphodon]

Probably graphics and/or keyboard related. See page 28. For example, if a program hooks int 9, it's going to wait forever for a keypress that never happens.

I’ll admit to only skimming it, but that doc seemed to be almost entirely about BIOS calls. I’m curious what if any hardware facilities the Mindset has to replicate PC hardware on a register compatible level.

For instance, its graphics hardware *can* mostly fake CGA’s graphics modes in terms of framebuffer layout and you can set them with a compatible BIOS call, but the manual didn’t seem to say anything about faking, say, the CGA mode register, let alone the CRTC registers. It looks to me at first glance that anything that doesn’t use the BIOS call is likely to fail right there?

 

[Plasma]

I wondered about keyboard.. but it does respond to that in many cases. Test drive will sit there at the select car screen.. its only when you hit enter to carry on that it locks up.

Calling int 16 or int 21 to read the keyboard should work. The problem would be games that install their own int 9 handler.