On Fri, 13 Apr 101 g.baltissen@hccnet.nl wrote: > Hallo David, > > > Remember: the 8237 will be clocked from the ISA bus, which runs at > > 8mhz! ;) > > Yes, on a PC. Remember the project to let a C64 run at 2 MHz? You had to > replace the DRAM with SRAM. And why? Otherwise you could not get around the > timing of addressing the original DRAMs. > Using an original C64 means you're stuck to the 1 MHz cyclus. The 8237 > needs four cycli. I already did some research to find out if I at least > could speed up a part of it but I found no holds to synchronize the 8237 > with the C64 at the right moment :( > > This simply means the ISA-bus has to run at 1 MHz. The ISA bus cannot run at 1mhz. A fair number o fcards might be using this as a timing source, and it will throw things off big. We have an 8mhz signal, its called the dotclock. THe ISA bus has a method for dealing with slow devices. Its called wait states. Our commodore will use them ;) For synchronization, the c64 also has waitstates. Have a look at the RDY line. When doing DMA, it doesnt matter, as ISA is plenty fast bto be able to squeeze one byte in per c-64 cycle. > > Groetjes, Ruud > > http://Ruud.C64.org/ > > > > - > This message was sent through the cbm-hackers mailing list. > To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tml.hut.fi. > - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tml.hut.fi.
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