Subject: Re:  Imitating the DPS-PAR ??
Date: Wed, 18 May 1994 21:53:41 -0400
From: "Alexander G. M. Smith" <agmsmith@gabriel.resudox.net>

Hannes Heckner <hecknerh@informatik.tu-muenchen.de> wrote
on Thu, 19 May 1994 00:05:26 +0200:
>Would it be possible to programm a device for the Amiga that
>uses a harddisk on its raw-format ignoring any file-systems on
>it. This harddisk could then only be used as a animation device,.
>but so is the harddisk for the DPS PAR.

Yes, but there are bottlenecks in places you don't expect them,
and others that don't exist.  Raw IO doesn't save you much,
I did tests (with 1 meg reads) on an A3000T and got 2.1 megabytes
per second raw, 2.0 with the normal fast file system.  Better
hard drives now go up to 3.0 MB/s.

The big bottleneck is in the chip ram bus, something around
1.5 MB/s on that A3000T (roughly).  My friend with the A3000T
had the same idea as you did.  Performance with 4 bitplane DCTV
was terrible (the chip ram bottleneck is more restrictive) and
got better but still noticably jerky speed with 3 bitplane
overscanned pictures.

If you want to try it out, the software is still around (and
unfinished), and should be on AmiNet.  Look for AGMS#?Film.
There are other better packages out now, but they still have
the chip ram bottleneck (maybe not a problem on an A4000 with
the faster AGA chips?).  On the other hand, the newer hard
drive playback programs use compression so they should be
good for scenes that are largely static, only redrawing the
parts of the screen that change, and thus avoiding the
chip ram bus bottleneck (unless you like moving the camera
around like I do).

- Alex


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