From: Gideon Zweijtzer (gideonz_at_dds.nl)
Date: 2002-05-02 08:07:59
|Hello Gideon, | |>"thinking" that they are running from $0000-$ffff. Another feature will be |>protection and bus-selection. The latter is necessary to define regions |that |>are not memory, but I/O. Memory accesses will go to the SDRAM bus, I/O |>accesses to the original address/data bus. | |Memory accesses (at least selected ones) need also go to the original |address/data bus elsewise the VIC chip will not see anything to display? It is a good thing that you mentioned this. This means that the MMU requires to have a mode to support writeback or write through to the I/O bus as well. Of course it should be selectable, so that's up to the user to program it in the MMU for which pages this applies (Note that on the C-64, the bus bandwidth to memory is only 1 MB/s!! Fortunately, this is a lot higher already on the C=1, but still less than the SDRAM bus). I would have found out sooner or later, but it's better to include it in the design from the beginning. Gideon Message was sent through the cbm-hackers mailing list
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