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From: jow@unccvax.UUCP (Jim Wiley)
Newsgroups: net.micro.cbm
Subject: RE Flames Re: "Valid" AMIGA info.
Message-ID: <220@unccvax.UUCP>
Date: Thu, 20-Jun-85 14:49:15 EDT
Article-I.D.: unccvax.220
Posted: Thu Jun 20 14:49:15 1985
Date-Received: Sun, 23-Jun-85 04:47:45 EDT
Organization: UNC-Charlotte
Lines: 30

>>     One of the nicest features of  the
>> graphics hardware is that it uses  the
>> "off-phase"  periods  of  the   system
>> clock, when the processor is not using
>> the  bus.
>
>This is really interesting, since the 68000 *has* no "off phase", unlike
>the Motorola 8-bit chips.  In fact, the 68000 is pretty much bus-bound,
>and there isn't a lot of spare bandwidth to go around.  There is a smell
>of snake oil in the air...
>
>> sound and i/o for the most  part  run
>> in the background, without  taking  up
>> any processor time at all.   
>
>On a machine as bus-intensive as the 68000, hardware that also wants the
>bus is definitely going to slow the cpu down substantially.  Maybe not as
>much as if the cpu were doing the work, but it won't be trivial.

Well, the 68000 does not have an "off phase" clock but a 68000 running
at 8 MHz has a 500 nanosecond bus cycle.  By using less that 250
nanosecond cycle time ram, the memory can be interleaved between the
processor and external hardware.  No bus requests, *NO* processor
slow down and optimum utilization of bus bandwidth would result.  It
sounds like this may be what they are doing but I don't really believe
that original posting.  When I hear the official word, then I will
believe something.

Jim Wiley
DATASPAN INC.