From: jornmoe@fredrik.atari.no (Joern Moe)
Newsgroups: comp.sys.atari.st
Organization: Atari Corp. Scand. AB (Norway)
Subject: Re: TT Compatability questions
Keywords: TT, ST, compatible, games, applications
	<1992Sep3.115337.3528@cs.hw.ac.uk> <H.2jCeQ8EYz7o@fredrik.atari.no>
	<1992Sep7.090500.20341@cs.hw.ac.uk>
Reply-To: jornmoe@fredrik.atari.no
X-Software: HERMES GUS 1.03 Rev. Apr 14 1992
Date: Tue, 08 Sep 1992 20:36:36 MET

In <1992Sep7.090500.20341@cs.hw.ac.uk>, Neil Forsyth writes:
>The hardware addresses in the ST, TT and Falcon are the same (additional
>features being an exception). The MMU is programmed to map $FFxxxxxx to
>$00xxxxxx so there is no problem.

On the TT, this is not the case. Several TT spesific hardware and RAM is in
the area above $00xxxxxx. Some games uses the highest byte in the address
registers, and on the TT this really f***s things up! In the Falcon, there is
NOTHING above the $00xxxxxx area, so whatever is in the high BYTE, will never
even go to the MMU, and hence is never decoded!! THIS fact is one of the
reasons that the Falcon should be more (M)ST(E) compatible than the TT.

>My 'game code' works on all machines why can't others?
Good for you, but sad to say, not many make 'clean' code!!

>If a programmer sticks to Atari's developer guidelines then *ALL* Atari
>680x0 machines are compatible.
>
I agree! But given the limited (compared to the current standards) power of the 
ST, you often have to do dirty trics to get the speed you want....

>>Third, the falcon is a consumer product, the TT is not! This beeing a fact 
>>makes it obvious why Falcon has to be more 'old-ST-games' compatible than
>>the TT was.
>
>I view the TT as being to the ST what 486DX-33 PC's are to 386SX-16 PC's.
>They are every bit as commercial. If you buy a PC game these days you can bet
>it will work on any PC. This should be true of ST games on the Falcon.

This comparison is not good! The only difference between 486DX PC's and 
386SX PC's is the processor. The rest of the machine is the same! The ST is a
machine designed as a keyboard home-computer. The TT is based upon the hardware
of the ST, but have essential additions to make it more 'business'-oriented.
Like internal harddisk, VME-bus, SCSI-bus, higher resolutions, LAN port etc.


>Most of the games that don't work with faster processors and caches are
>written by f*ckwits that go straight for the DMA/FDC hardware directly. This
>is because their software timing loops get shortened. Why didn't they use
>the BIOS or even XBIOS calls?
>Atari are now recommending that Falcon (and I guess ST) games work on hard
>disk and use copy protection based on word entry from a manual.
>
>To sum up, I have tried running a *LOT* of ST games on a Falcon and less than
>10% of them worked. This is one reason I think the Falcon will fail if markted
>as a games machine. The available leisure software will be small.

Only 10%? Wether this is bad or not depends uppon the quality of these games!

>Only a couple of the games worked after disabling the cache and setting
>the speed to 8Mz. Since most games that load from a bootsector and don't use
>system calls failed I assume that they were not 68030 compatible.
There is only two things a programmer can do which a proper written trap-
handler on the 68030 can't handle to make it 100% compatible (with cache off). 
Those things are speed depended code and self writen trap routines!!

>Atari were not to blame for these incompatibilities however I do blame them
>for not kicking butt when the TT didn't run software. Programmers should have
>learned their lesson back then.

Actually we agree on the lousiness of game-writers. I do howewer think
that the Falcon is as ST(e) compatible as the MSTE (with cahe and 
16MHZ on) but with additonal problems with trap's as mentioned above!

PS. Do you have a Falcon???
-- 
  _______________________________________________________
 / Joern F. Moe /  All above is my own personal opinion! \
/ Oslo, Norway /  Any lack of opinion above is also mine! \
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