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But why is that? It still seems to me almost like magic. The computer is Amstrad PC2086/30, and the game that I have to run first is either The Cycles: International Grand Prix Racing or Grand Prix Circuit, both by Accolade. If I don't do this, the games such as Prehistorik or Dangerous Dave (1990, Softdisk) won't run, the screen turns black, and the reboot is the only thing that helps.

The games that don't need this trick are, for instance, Prince of Persia and Golden Axe.

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  • My guess, and it's only a guess, is that by running that game first, it loads a dependent piece of code (eg. dll) into memory that the other games use. – rrirower Dec 20 '13 at 16:47
  • these programs are all pre-internet. you will probably not be able to find out unless you do the detective work yourself. Start with what the failing games say/log when they fail. – Frank Thomas Dec 20 '13 at 17:10
  • I gotta give you props for keeping a 8086 up and working. haven't seen one of those since the late 80's. – Frank Thomas Dec 20 '13 at 17:12
  • DLLs on DOS? Lol. – LawrenceC Dec 20 '13 at 17:54
  • DOS does run under Windows. Lol. – rrirower Dec 20 '13 at 17:59
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The games are probably loading a TSR which is handling some non-standard piece of hardware.

Amstrad machines were not always 100% compatible with other PC makes and there were a number of tricks used to get some device or graphics drivers to work well. The TSR (Terminate and Stay Resident) trick was common in DOS and provides an intercept for the Page Zero software interrupts.

My guess is that a couple of your games are Amstrad-friendly and load the TSR for their own use. The other games only work once this driver is present.

If you have other old bits of software, like Norton Utilities, then you should be able to interrogate what TSRs have been loaded. You can try the DOS command MEM /C which might also help.

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I'm guessing the onboard video of this system (onboard from what I could tell after a brief look) isn't quite 100% VGA compatible. It could also be subtle BIOS incompatibility.

It's unusual that some games would be able to put the VGA in a state that other games would not have a problem with on initialization. I would surmise your first games are using the BIOS to set up video modes, and the second are talking to the VGA hardware directly. So maybe the BIOS is doing something extra to the hardware that allows the second games to run. It could be the reverse as well.

If it's possible, try scouring auction sites or computer shops for an old ISA VGA card and disable the onboard video.

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  • wow... an ISA VGA card... you'll find those next to the SIPPs and MFM drives. – Keltari Dec 20 '13 at 20:03

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