ATARI 800 EMU
V1.0
by
David Firth/Petr Stehlik
This is probably one of the most incredible pieces of software ever to hit a
Falcon hard drive. Very simply put, it is a more or less complete Atari 800
emulator!
How is this so? Well, we have the persistence of David Firth, who started a
portable cross-platform freeware 8-bit emulator for the old Atari. And Petr
Stehlik, for taking the time to make it work on his Afterburnered Falcon.
There has been a lengthy history of trying to get the venerable 800 series
to work on succeeding Atari hardware. Even from the earliest days of the ST,
where the programmer of GEMulator decided he wanted to transport some of
that 8-bit magic across to his whizzy new 16-Bit ST.
I've never seen or tried out the end result, but I believe it did quite well
within the limitations imposed on it by the ST's hardware. Which meant
almost nothing that needed any exotic graphics modes or dabbled too deeply
into machine language, could actually run. The problem was, that the design
philosophy for the different generations of Atari hardware were too far
apart from one another. The 800 having more in common with the Amiga, with
its various custom hardware, and indeed having the main designer, Jay Miner,
in common too. The ST, which influenced succeeding generations of TOS
computers, was more 'off the shelf' in its conception, and less flexible
than the 800, in some respects, for all the extra CPU power it had.
It really took a few more years of hardware evolution, for the new Atari
generation to start to catch up with the Atari 800 ;-)
The next best chance came with the Atari Falcon, which cranked up the CPU
power a bit more, and also managed to break free of the miserly sixteen
colour onscreen graphics limitation. Which is almost where our story starts
to come up to date.
They soon found out although the Falcon had more to offer in the hardware
stakes, it still wasn't really an ideal platform for emulation, especially
as it was mainly CPU dependent, like the ST, and what custom hardware it
had, such as the DSP, could not help too much in this sort of case (except
maybe for sound emulation.) It also wasn't really (hand on heart!) fast
enough for the job.
Some people took things further, and spent serious money, acquiring serious
levels of CPU power. In a brief exchange of email with Petr Stehlik, he
advised me that the Afterburner '040 still was only able to hit 40% of
normal speed for the 800XL! - It may be the case that coding optimisations
have improved matters since then, but the fact remains, this is not an ideal
solution for owners of standard unaccelerated Falcons!
In the meantime, I had managed to do a bit of catching up, purchasing an
accelerator, which was not quite in the Afterburner class, but represented a
vast improvement over a standard Falcon, the Centurbo 2, which you are all
sick of hearing about by now! It was time to re-examine this beast, which
now stood at version 1.0.
The download unzipped to a .gtp file, activated by drag n' drop, various
ROM's, a MYDOS disk image, loads of doc files, some of which going into a
lot of detail, and a config file, to make sure it all ran together smoothly.
To run it, it is firstly a good idea to switch to a 256 colour screen mode.
Hi-res VGA is perfectly acceptable, if you like to look at an 800XL screen
in a small centralised window that seems some distance away ;) It is really
better to switch to a lo-res or 'double line on and 40 columns' mode, to get
a fully authentic screen experience. A short pause, and the familiar sky
blue with white text main menu of MYDOS comes into view.
A useful key to remember to press at this point, is F1, which brings up the
control menu for the emulator, whilst it is running. Disk management, which
lets you select disk images and assign them to any one of up to eight
connected virtual floppy drives. There is an option to run a program file
directly, if that is stored on your Falcon. (These come in various formats
often as *.com files.) A very useful sub-menu lets you select the type of
emulated 8-Bit you want to work with, including classic bog-standard 800XL,
the later 130XE, even a couple of different memory upgrades to Atari 320XE,
and the Atari 5200 console, based on the 8-Bit hardware.
Various others round up, including warm and cold resets, and the chance to
leave if you have to. The keyboard shortcuts for all of these are
prominently advertised.
It is perfectly possible to go in through the MYDOS portal at this stage,
staring in admiration at the options available, most of them not easily
understandable to first time users. Or it might be a better idea to go and
grab some disk images.
I'll give you a nice URL at the end of this article, to go and get some
demo's on disk, for that is the real true test of how good an emulator
really is. Will it run everything thrown at it, or will it gasp and splutter
at the merest hint of anything system illegal?
I am happy to report, that this emulator breezes the vast majority of
demoware, even coping with the newest ones. This seems to bear out
favourable reports for this emulator (in its DOS or Linux incarnation) in
the emulation scene, as it is seen to emulate the hardware extremely
accurately, even being capable of screen modes and tricks that no other
emulator can cope with!
The important issue is speed, or the lack thereof. From my testing on a CT2-
based Falcon, it feels as if this emulator is running at around 50% of
normal system speed. I say "feel", without having any benchtest software to
properly assess it, and basing that "feeling" on how the screen update
looks, which "feels" about half as quick as it should be!
I did try a couple of games, and the impression is similar to an early
version of Godboy on a standard Falcon, slow, but just about playable.
There isn't a lot of sound around. In fact, on the main *.GTP, there isn't
any. There is a faster and buggier version, with POKEY emulation, but this
has a nasty habit of stopping working, a short time later, and the music is
played back sluggishly and out of tune as a result.
That aside, serious bugs are rare. There is the odd program file, that
upsets things completely, but it isn't clear whether that is down to a
weakness in the emulator, or poor setting-up of the memory configuration, as
I seem to recall some 8-bit demos at the SV2000 needed extensive fiddling
with memory banks on these machines, before they decided to work.
The other interesting point, is that recent versions of the emulator have
been coded in a 'system clean' sort of way, which means that Milan and fast
TOS clone users might be able to get some sort of benefit from it? I also
await the arrival of some real computing power, in the form of the CT060,
the first viable '060 based accelerator for the Falcon. Then we'll see what
happens next!
In conclusion, the work put in by David, Petr, and others represents a
considerable technical achievement, in emulating so completely, a totally
'alien' system on an Atari TOS machine. It was kind of interesting to run a
demo (Drunken Chessboard) parts of which a normal ST (or Falcon?) would be
apparently unable to cope with! It is an excellent piece of software, if
you own an accelerated Falcon, as it is workable, but just too slow for a
standard machine. It is one which should 'grow into' any future Atari
hardware!
I look forward to a full-speed version with POKEY Sound, on a CT060!
Dead Hackers 8-Bit demo anyone!!
----------------------------------------------------------------------
Right, it's URL time for those people who are interested.
To get the latest version of the emulator, in Atari, DOS and Linux
versions:- http://joy.sophics.cz/a800.htm
To grab some nice demos on disk images, try this one:-
http://www1.tu-chemnitz.de/~sgl/atari/demosind.htm
If you hate typing in strange URL's, pick up the links from:-
http://cih.atari.org/magnews.htm
To get these images to load, make sure you grab the 'menu.atr' file and have
it handy. Drag and drop the 'menu.atr' on the main *.GTP program.
A screen, which is almost blank, apart from the title 'yogi/jellystone park'
at the top, then appears. At this point, hit F1, then select disk
management, put the cursor over D2, the first empty virtual drive, hit enter
and select your disk image (Important - Leave 'Menu' where it is in D1!).
Hit enter again and escape to return to the main menu. Then 'Select
system', and once that is done, press for a warm reset.
You should have a screen which has a couple of columns of demo titles, with
a letter alongside it. Pressing the corresponding key then loads that demo!
Easy, isn't it! (Hint, most of these mega-images have more demos than first
appear onscreen, press the down arrow/cursor key to get to these additional
screens.)
CiH - For Alive! - Oct '00
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