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General Category => Technical Support => Topic started by: ComSoft6128 on 16:39, 20 August 21

Title: DMA/AMSDOS/ParaDOS query
Post by: ComSoft6128 on 16:39, 20 August 21

Sample DMA by Futurs'
DMA sample from 1995, running on a 6128 Plus,  which seems to interrupt AMSDOS but not PARADOS?

Not sure what I'm seeing here - no joy with CAT under AMSDOS but Logging (CAT) a disc with ParaDOS (Cartridge) works fine.
So.......how can the sample play simultaneously while ParaDOS is working?
Is the DMA function processing the sample allowing the Z80 to work normally?
It's not causing any problems but I'm curious as to what is happening.

BASIC Listing & .dsk file at CPCPOWER:
https://www.cpc-power.com/index.php?page=detail&num=8924 (https://www.cpc-power.com/index.php?page=detail&num=8924)


https://www.youtube.com/watch?v=LTmen_8Msis (https://www.youtube.com/watch?v=LTmen_8Msis)


Other links:
https://www.cpcwiki.eu/index.php/Plus (https://www.cpcwiki.eu/index.php/Plus)
https://www.cpc-power.com/index.php?page=staff&lenom=Futurs%27 (https://www.cpc-power.com/index.php?page=staff&lenom=Futurs%27)
https://www.cpcwiki.eu/index.php/ParaDOS (https://www.cpcwiki.eu/index.php/ParaDOS)
https://en.wikipedia.org/wiki/Direct_memory_access (https://en.wikipedia.org/wiki/Direct_memory_access)


Not emulated - original hardware and software.
Please note that  the aspect ratio for this YouTube video is 16:9 but the CPC monitor
has an aspect ratio of 4:3 so you may wish to adjust your viewing device accordingly.
Title: Re: DMA/AMSDOS/ParaDOS query
Post by: pelrun on 08:37, 21 August 21
That's not AMSDOS it's interfering with, it's BASIC. It pulls HIMEM down really low (&FFF) and BASIC can't allocate 2K to read the catalog into. It would error out before it even calls AMSDOS.