Date: 02-18-93 (06:11)                 Message Number: 584    (63 of 70)
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  From: CRAIG GRAHAM                     Read: Public
Subject: F030 - Some technical com        Conference: U-COSYSATATEC
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From: [email protected] (Craig Graham)
Newsgroups: comp.sys.atari.st.tech
Subject: F030 - Some technical comments from a demo coder....
Message-ID: <[email protected]>
Date: 17 Feb 93 13:51:20 GMT


This is another post as a favour to Griff of Electronic Images (who only has
read access to the internet).

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The Falcon : A programmer/demo writers view!
            (and Falcon030 vs A1200!)

       Since I have programmed the Falcon I thought I better clear up some     details regarding the machines hardware.

The Blitter
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       The blitter on the falcon is basically a double speed (16mhz) version of
the STE blitter, which basically means that it is totally redundant.  The main
problem being that the processor is STOPPED when a blit is executed (or the
blitter can be run concurrently with the processor, the bus being shared in
64 cycle segments). An STE can move about 1.6megabytes per second with the
blitter, so a Falcon blitter can move about 3.2megabytes per second, but this
locks out the cpu, not allowing interrupts and isn't really very useful.
       Using the 68030 in the Falcon (in 320 * 200 true colour mode) you can   move about 10 megabytes per second (or about 200k per vblank!) so why bother with the blitter.  Since the 030 has a barrel shifter and data/instruction cache then any screen operations you want to do (sprites/scrolling etc) can be acheived using the cpu in about half the time it would take the blitter in hog mode.
Example:
       In true colour mode 320*200, I wrote a texture mapping routine using the030 that drew a texture mapped rotating cube at 25 fps(the cube was 190 pixels high).Now trying doing that with an A1200! (oh i forgot the A1200 can only have 8
bits per pixel and has no byte/word pixel mode! Don't be fooled by Amiga people telling you how wonderful the A1200 blitter is, because its not!)

Sound Hardware
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       The sound hardware on the Falcon is wonderful.  The Protracker player
(now at atari.archive.umich.edu) I wrote for the Falcon plays modules at 50khz
using 15bits per channel(two 16bit stereo channels). For anyone wanting to
know the technical details, the player uses 32 bit interpolation and an 8bit
to 15bit volume conversion table and takes about 30-35% cpu time, but i guess
when people learn to use the DSP it will take about 3% cpu time! The sound
quality is great, better than any Amiga.

       A friend of mine (Douglas Little of Photochrome fame) told me a really
neat trick using the sampling hardware. You can clear the screen VERY quickly   using the sound DMA by sampling 8channels at 50khz directly to the screen, so
you can effectively clear the screen using no cpu time (with only a few bus
cycles lost).

DSP
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       I didn't have the time (or documentation) to mess about with the DSP,
however by dissassembling the ROM I worked out that it should be possible to transfer from DSP to CPU memory at about 3-5 megabytes per second, or 1 mb/s using
one of the operating system routines. The DSP will be able to rotate about one
million vertices per second!!! Which is approximately 10 times faster than
an 020 or 030 could manage. The Falcon will blow the A1200 away when it comes
to 3d games.
        The DSP reference book is very difficult to get hold of, but I've got  one on ordered - it costs about 60 pounds.


Regards.
Martin Griffiths ([email protected])
(aka Griff of Electronic Images)

PS. Buy a Falcon, I think Atari finally got something right!

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There you have it...........as always, don't email me for this one, I don't
know the answers.

Craig Graham.     /\  E-mail:[email protected]
BAe Space Systems ||  Phone : (UK) 091 2737650
Stevenage,England.||  Snail-mail: 38 Brighton Grove, Fenham, Newcastle, England.
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 SPACE the final^^^^frontier. Seen it,done it,read the book,got the T-shirt....
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