UMBPCI on 440ZX chipset, ISA-DMA problem \ VOGONS

UMBPCI on 440ZX chipset, ISA-DMA problem

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First post, by jwt27

Posted on 2011-09-10, 16:12

jwt27 Offline

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Location: Fryslân

A friend of mine is building a DOS machine, he has a Fujitsu mainboard with 440ZX chipset and a PhoenixBIOS.

Now we tried to set up UMBPCI for UMB management, it sets up the UMBs fine in C800-DFFF but DMACHK shows that ISA-DMA doesn't work in that memory region. No problem we thought, just set up UMBPCI to use E000-EFFF but it seems that the system bios is shadowed there (wtf?), and there is no way to disable it in the BIOS setup.

Now my question is, do we need ISA-DMA? And what is it exactly, I suppose it means that ISA devices don't have DMA access in that region? The only ISA card he uses is a sound card which is PnP.

Reply 1 of 3, by h-a-l-9000

Posted on 2011-09-10, 17:02

h-a-l-9000 Offline

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> The only ISA card he uses is a sound card which is PnP.
And the floppy drive.

As soon as any program tries to use this memory area for DMA transfer it will fail. Question is, can that be prevented...

1+1=10

Reply 2 of 3, by jwt27

Posted on 2011-09-10, 17:22

jwt27 Offline

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If the floppy drive is on ISA, is it possible that the IDE controller uses the ISA bus too? We tried to copy some files from CD yesterday, and it crashed. CD drivers were loaded in UMB..

Reply 3 of 3, by h-a-l-9000

Posted on 2011-09-10, 17:33

h-a-l-9000 Offline

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For a PentiumII chipset I'd expect it to use PCI DMA, but I'm not very familiar with inner IDE DMA workings. You could set the drive to PIO in the BIOS to check.

1+1=10

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