Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!usc!jarthur!bridge2!3comvax!tymix!tardis!jms
From: jms@tardis.Tymnet.COM (Joe Smith)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: HardFrame Still the Best?
Summary: DMA to Fast RAM still slowed by Chip RAM
Message-ID: <1317@tardis.Tymnet.COM>
Date: 31 Oct 90 00:27:11 GMT
References: <9010172027.AA03829@hamlet.acc.uncg.edu> <90297.223722IO92257@MAINE.BITNET> <6381@ethz.UUCP> <04619.AA04619@babylon.UUCP>
Reply-To: jms@tardis.Tymnet.COM (Joe Smith)
Organization: BT Tymnet, San Jose, CA
Lines: 18

In article <6381@ethz.UUCP> visinfo@ethz.UUCP (VISINFO c/o
Sascha Schnapka) writes:
>>      The tool had an optional 'DMA contention' which
>>      turned on all bitplanes, copper and stuff.

In article <04619.AA04619@babylon.UUCP> cbmvax.commodore.com!cbmehq!babylon!rbabel (Ralph Babel) writes:
>Who cares - as long as DMA is to and from Fast-RAM?

But DMA to Fast RAM cannot be done without the CPU's permission.  The CPU
cannot grant permission if it is hung up waiting for a previous access
to Chip RAM to go through.  DMA directly to/from Fast RAM is still impacted
to some extent by overscanned 16-color hires screens.

-- 
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