Dos 6 conventional memory tricks

Getting old software/games running on older hardware.

Re: Dos 6 conventional memory tricks

Postby Baoran » 2018-11-27 @ 18:48

elianda wrote:You already wrote this. Since you noticed that Floppy does not support DMA any more when E000 is included then DMA when attributed as page frame won't work as well.

Usually DMA stops working if the UMB is generated by Shadow RAM when the mainboard does not support DMA from Shadow RAM or if UMB is generated from XMS regions where no DMA is possible. For ISA DMA generally there is a 16 MB limit. I don't know how HIMEMX provides XMS to EMM386 to generate UMBs, but the /MAX=65536 indicated that you enable more than 16 MB. Now if the XMS that is provided by HIMEMX to be mapped at E000 for virtual EMS is from an area beyond 16 MB physical it could be the source of non working DMA.


Changing himemx to normal himem.sys didn't change anything. Changing the limit to 8Mb with himemx didn't change anything either.
I have been going through the memory with umbinfo and it seems that only free space for umb seems to be B000-B7FF and D300-DFFF and that is why emm386 can't find any 64Kb empty block for the frame. Umbinfo won't even show what is in E000-EFFF and it just skips over that, so I can't tell what has exactly reserved that.

Not sure what kind of problems Frame=none would cause with emm386.
Baoran
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