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Re: Disk drive speeds

heuser.marcus@freenet.de wrote:

IIRC the clock of the Atari is indeed nominally higher (ca. 1,78 MHz)
than both the "standard" Apple or a C64 but it is enormously slowed by
the DMA of the screen controller ('ANTIC'), which can halt the cpu at
"will".


A curious design choice, in view of the beautiful pecliarity of the
6502 that it accesses RAM on only one phase of the clock, making
zero-interference video DMA trivial (as in the Apple).  Of course,
if the ANTIC would otherwise interfere with the video refresh accesses
(in the visible part of the raster), then interfering with the CPU is
the easiest course.


I have no exact numbers but I read something about an effective clock
of 0.9-1.0 mhz - in other words: Picture generation eats half the cpu
time thus making it theoretically comparable to the other systems.


That squares with my informal 1980 benchmarks at the local Computerland.

-michael

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