::> Most other-than-IO functions performed during I/O such as graphics, sound,
::> etcetera on the Atari 8-bits utilized the fact that for 1 60th of a second
::> the screen is not painted. While the 'vertical blank' was occurring you
::> had several cpu cycles available. If you wrote very tight code you could
::> do a lot in those few cycles. On the Atari this was accomplished by GTIA
::> 'display lists' which are programs for the GTIA coprocessor.
::
::Apple interleaved graphics output (and DRAM refresh) with CPU cycles. This
::works because the 6502 only performs memory accesses at very predictable
::times. So there are no vertical (or horizontal) blank intervals in which
::the CPU is not doing something else.
I knew I liked the C64's setup better, even if I complain about VIC-II
DMA freezing the processor every eighth screen line.
--
----------------------------- personal page: http://www.armory.com/~spectre/ --
Cameron Kaiser * Point Loma Nazarene University * ckaiser_at_ptloma.edu
-- Klein bottle for immediate occupancy; inquire within. ----------------------
Received on Thu May 18 2000 - 21:40:11 BST