Atari Emulation

by Matthew Preston

Emulation, we hear the phrase every day, it gets bad press with big headlines about big software companies taking each other to court. This is not a new phenomenon, emulation has been with us for some time now and many people put it in the same frame as "to steal". A few years ago I would not have thought twice about emulating an Atari but with the big "A" making a come-back we must be aware that the games people play and the software that runs them belongs to somebody.

The new generation of mobile phones re-opened the market for handheld games and we may see a few old favourites re-live their former glory. But this also means the lost and forgotten software many thought Atari would never worry about could cause a few problems for a lot of Atari die-hards. If you want to know more, a good place to start would be www.atari-history.com

I am a relatively new PC owner and own many original and working 8-bit machines, not all of them are Ataris. From the age of ten I have had my 800XL, it has a few friends now for spares and such, that’s another eleven 800XLs, well I never could pass a good boot sale or trip to the Alternative Micro Show at Bingley Hall. Being a few years older now and cursed by my lust for ever increasing power of my PC I wondered if with all this super technology it could emulate a real computer? A quick search on the internet for suitable emulators came up with several suggestions, ranging from simple projects to full-blown emulations of the complete hardware. I cannot hope to cover this subject in one article so will start by introducing a few then take you through setting them up and comparing them using my own experience as a guide.  

How do you go about emulating an Atari?
There are two camps on this one, simulate the operating system, or emulate the hardware. There is no right or wrong answer; you have to decide what you want to use the software to do. As a rule of thumb, early games work fine on a simpler OS simulation, while demos and later games require a more complete solution. You are not restricted to the Windows platform either, as there are emulators for DOS, Windows 3.1, Unix, Linux, BeOS, Palm OS, Pocket PC (Windows CE), EPOC (Psion) and OS2.

To set about emulating an Atari takes great skill and patience, the hardware is quite simple compared to today’s technology, but I would imagine it is quite a complicated process to go through. Can you remember what is inside an Atari 8-bit? You have a custom chip the 6502C CPU made for Atari, and then there are POKEY, FREDDIE, CTIA, GTIA, ANTIC as well as the BASIC ROM. Field service manuals are available but they only tell you how they are connected, not what they contain. 

Where to begin?
Early emulators did not bother and with early PCs' feeble processing power a simple OS simulation was the only option. Many authors began by emulating each chip in software. This way you can build a virtual machine in software piece by piece until you get a working prototype.

I find it interesting that the programmers encountered the same timing problems that the hardware designers did at Atari. This is more of a problem when emulating the hardware because the 6502 CPU does not process everything. You see, for its day the little 8-bit was quite advanced, using dedicated chips to take control of tasks such as the graphics display, keyboard input, sound generation, I/O, memory management and using the CPU to house-keep the lot making sure everything came together. If you get the timing wrong then everything begins to fall apart quite rapidly with the CPU doing its best to keep it together, the result is a slow emulation that is unstable.

I have been following the progress of several pieces of software and have been impressed with the terrific progress made. I would like to introduce what I consider to be the best software available to emulate the Atari 8-bit, the unfortunate thing is that not everyone will be able to use it because it is not cross-platform and only works in Windows 9x (however, the code it is based on is, and I will review a few of these next time).

The software is called, "Atari800win Plus" and has not been created by a single author but developed over time by too many people to list. The two main names to remember are Richard Lawrence, who developed the Win32 code for Windows and Tomasz Szymankowski, who continued Richard's work to improve an already good emulator. The software is completely open source and falls under the GNU license covering public domain software for the internet. However, I must stress that the software which runs on the virtual machine is not for GNU, and as such cannot be packaged with the free download. It is quite possible to take the software from your old Atari machine and put it in the virtual machine, whether this is legally any better than using a copy that someone else has done I don’t know and is not for discussion in this column. Let’s concentrate on what we can do!

Finally, I must confess that emulation is quite an addictive thing, I have emulators on my old PC notebook, main PC and network it to my old PC to both run the emulator and play games while I am the other side of my computer room. The final screen-shot (below) shows what can be done if you have the patience and are mad enough!
 

That's all for now, next time I will take a look at the other platforms on which you can run an Atari, including some of the above.
 

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MyAtari magazine - Feature #4, February 2002