Subject: Re: more -current error
To: Tom T. Thai <>
From: Jukka Marin <>
List: current-users
Date: 06/18/1997 16:41:04
On Wed, Jun 18, 1997 at 08:34:07AM -0500, Tom T. Thai wrote:

> > While the 1542CP is an OK card, it is definitely not my choice for
> > a system where you want real performance.  If you're using more than
> > 16M, some transfers will be "bounced" (i.e. lots of data copies!).
> I thought that buffer bounce was fixed recently?  I think I read it on 
> the list?

Sure, but any ISA card can only DMA to the first 16 MB of RAM because the
address bus has only 24 address lines.  If you want to use more RAM with
a 1542 card, the CPU has to copy the data between the bounce-buffers in
the lower 16 MB and the actual buffers located anywhere in the CPU address

So, it _works_, but it's _inefficient_ and _it cannot be fixed better than
this in software_.



                       1503 kHz @ 22:30 EET DST Mon-Fri

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