Re: DMA INTERFACE for SAM COUPE
DMA transfer in MODE4 (time in border area = fast memory) transfer one byte per 8T http://velesoft.speccy.cz/other/dma%203Trd+3Twr-mode4.png DMA transfer in MODE4 (time in screen area = contended memory) transfer one byte per 16T http://velesoft.speccy.cz/other/dma%203Trd+3Twr-mode4-contended.png 11904 bytes per one frame 50Hz is maximum speed in mode 4 with active screen. With external 1MB memory can be dma transfer faster. DMA scroll can move screen data from external ram to internal ram. Access to external ram is always fast(uncontended). VELESOFT Dne 9. 8. 2015 v 3:06 Simon Owen napsal(a): Very interesting. I didn't expect it to work well enough to be of use on SAM, given how limited memory accesses are. Does the CPU manage to run at all while the DMA is active? Is it possible to achieve the same result with an external board replacing the internal CPU? My soldering skills aren't up to replacing the existing CPU with a socket! Of course, your news might trigger you-know-who into action again... Si On 08/08/2015 23:46, VELESOFT wrote: Here is my version of DATA-GEAR (Z80 DMA interface for SAM COUPE). It's internal version for connection instead original Z80CPU (need replace CPU with socket). http://velesoft.speccy.cz/other/dma%203Trd+3Twr-long.png VIDEO (sorry, bad quality and low FPS). Almost fullscreen scroll 25 fps on real sam coupe. http://velesoft.speccy.cz/other/DMA_SAM_001.MPG --- Tato zpráva byla zkontrolována na viry programem Avast Antivirus. https://www.avast.com/antivirus
Re: DMA INTERFACE for SAM COUPE
Now run DMA stable only with fast block transfer (disconnect CPU and stransfer data). I will test soon also byte mode = DMA transfer only one byte and return to CPU. I must make counter which set speed of DMA transfer. Yes, is possible also make external DMA interface VELESOFT Dne 9. 8. 2015 v 3:06 Simon Owen napsal(a): Very interesting. I didn't expect it to work well enough to be of use on SAM, given how limited memory accesses are. Does the CPU manage to run at all while the DMA is active? Is it possible to achieve the same result with an external board replacing the internal CPU? My soldering skills aren't up to replacing the existing CPU with a socket! Of course, your news might trigger you-know-who into action again... Si On 08/08/2015 23:46, VELESOFT wrote: Here is my version of DATA-GEAR (Z80 DMA interface for SAM COUPE). It's internal version for connection instead original Z80CPU (need replace CPU with socket). http://velesoft.speccy.cz/other/dma%203Trd+3Twr-long.png VIDEO (sorry, bad quality and low FPS). Almost fullscreen scroll 25 fps on real sam coupe. http://velesoft.speccy.cz/other/DMA_SAM_001.MPG --- Tato zpráva byla zkontrolována na viry programem Avast Antivirus. https://www.avast.com/antivirus
Re: DMA INTERFACE for SAM COUPE
Very interesting. I didn't expect it to work well enough to be of use on SAM, given how limited memory accesses are. Does the CPU manage to run at all while the DMA is active? Is it possible to achieve the same result with an external board replacing the internal CPU? My soldering skills aren't up to replacing the existing CPU with a socket! Of course, your news might trigger you-know-who into action again... Si On 08/08/2015 23:46, VELESOFT wrote: > Here is my version of DATA-GEAR (Z80 DMA interface for SAM COUPE). > It's internal version for connection instead original Z80CPU (need > replace CPU with socket). > > http://velesoft.speccy.cz/other/dma%203Trd+3Twr-long.png > > VIDEO (sorry, bad quality and low FPS). Almost fullscreen scroll 25 > fps on real sam coupe. > http://velesoft.speccy.cz/other/DMA_SAM_001.MPG
