digger wrote on 2024-06-05, 22:04:

I remember that Dune II only supported 8-bit sound cards, which would only allow DMA to conventional memory (the first 1MB, even on 286+ systems). And also it didn't use a 32-bit DOS extender, because it also ran on 286 systems.

I don't think that's right, since the DMA addressing is handled by the 8237 and the page registers, not whether the card is an 8-bit or 16-bit card. The floppy controller is also 8-bit and the DMA limit is 16MB and not 1MB for those.

I believe I found it's "source"? (Possible source for binary?)?:
A little confusing.... unsure if this is helpful

Page 87: https://www.cpcwiki.eu/imgs/2/28/Amstrad_CPC_ … ual_English.pdf

The memory manager EXTMEM.SYS The program provides a uniform interface to access extended memory available. The programs therefo […]
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The memory manager EXTMEM.SYS
The program provides a uniform interface to access extended memory available.
The programs therefore do not have to worry about the management / response of an extension of RAM.
Even if the memory is fragmented. EXTMEM.SYS comes on Side B Disco BonnyDOS (Inicron version and compatible with maximum magnification of 512K RAM).

I have located it as "EXTMEM.APL", again slightly confused

digger wrote on 2024-06-05, 22:04:

I remember that Dune II only supported 8-bit sound cards, which would only allow DMA to conventional memory (the first 1MB, even […]
Show full quote

I remember that Dune II only supported 8-bit sound cards, which would only allow DMA to conventional memory (the first 1MB, even on 286+ systems). And also it didn't use a 32-bit DOS extender, because it also ran on 286 systems.

So I guess the programmers of that game would call INT 15h to copy digital samples and other game asserts to conventional memory whenever needed, and then access it there.

But thinking more about that, that would be a slow operation for on-the-fly stuff such as sound effects, especially on 286 systems, which were slow to switch to protected mode and back to real mode each time such INT 15h calls would be made.

I wonder why the game didn't use EMS instead. Probably because it was targeting 286 systems, which were more likely to have XMS than EMS?

Speaking of games, Space Quest collection mentions Extended Memory in the installer, too.

GeoWorks 2, as well.