Path: utzoo!yunexus!ists!jarvis.csri.toronto.edu!mailrus!wuarchive!texbell!texsun!convex!eugene!swarren
From: swarren@eugene.uucp (Steve Warren)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Hard disks, DMA vs Non-DMA
Message-ID: <3197@convex.UUCP>
Date: 18 Nov 89 00:20:15 GMT
Article-I.D.: convex.3197
References: <8911150430.AA24506@jade.berkeley.edu> <127914@sun.Eng.Sun.COM> <1989Nov16.185706.29328@sjsumcs.sjsu.edu>
Sender: usenet@convex.UUCP
Reply-To: swarren@convex.COM (Steve Warren)
Organization: Convex Computer Corporation, Richardson, Tx.
Lines: 25

In article <1989Nov16.185706.29328@sjsumcs.sjsu.edu> 33014-18@sjsumcs.SJSU.EDU (Eduardo Horvath) writes:
>
>	Can you DMA directly into FAST RAM, or is it necessary to go through
>	CHIP RAM?  If a controller DMA'd into FAST RAM, wouldn't that solve
>	the problem of contention with the custom chips?

Yeah, but when the data is needed in the chip space (sound data or
graphics data) or when the machine is all chip ram, then you still
need to move the bytes into contention-land.

When the destination is fast ram there isn't a problem.

On the same subject, has anyone seen the misleading product sheet
put out for the KRONOS SCSI controller?  It claims that DMA is
fundamentally flawed when trying to access chip ram.  This is
absolutely false.  Certain controllers were not designed to allow
for contention gracefully, but the fact that they were DMA was
irrelevent.  The only reason the KRONOS is fast is because the
controller-to-memory path is 16-bits wide.  If they would just
say it like it is I would be more impressed with their product.
I am suspicious when they erect straw men.

--Steve
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