While doing a little net surfing looking for more Sinclair resources on the net, I ran into a mention of a ZX81 emulator for the Atari ST. Having recently picked up an ST, I decided to try the emulator out.
After a few machinations and a call to a local Atari user group, I was able to get the file to an ST TOS disk. This is the first program that I’ve downloaded off the Internet and transfered to the Atari.
After the program loads, it brings up an introduction screen with a nice picture of Sir Clive. Clicking on GOTO ZX81 takes you to the emulator. The screen clears, there is a pause (just like the real ZX81), and the familiar K cursor appears.
It’s been a while since I played with my ZX81, so I forgot where most of the keys are. Hitting the HELP key will bring up a big display of the ZX81 keyboard. This feature is available at any time in the emulator. It’s fast to pop up and disappear so it only takes a second to look up a key.
One other special key for the emulator is the UNDO key. (For those unfamilair with the ST, it has two keys acutally called HELP and UNDO.) Hitting the UNDO key brings up a window with the following selections:
Power Pack – Lets you select 1K, 16K, or 48K memory.
Joystick – Lets you reconfigure the keys used for cursor movement, instead of the usual 6, 7, 8, & 9.
Cont – Resumes the emulator.
Break – Stops the program in progress and clears the screen. For Basic programs the space bar still works as the break key.
Reset – Reset the emulator to its original settings.
Quit – Leave the emulator.
The speed of the emulator is about that of the original ZX81, at least the speed I recall. I have not run any benchmark tests to compare it with the ZX81.
Another neat feature is LOAD “”. Instead of the usual loading of the first program found on the tape, it pops up a window and gives a directory of ZX81 files (*.81). You can then use the mouse to select a file to load. All LOADs and SAVEs are to the disk drive.
The emulator comes with about 30 ZX81 programs. Some are written in Machine Code and run fine. Since the emulator was written in Germany, some of the programs have German prompts. Most of the programs are games, some adventure and some arcade, but there are some utilities too. There seems to be an assembler and disassember (did not try them out).
The emulator comes with little documentation. The original German documentation is very short. There is one English document that was written by a user that found the emulator on a BBS. It seems to be more thorough than the German docs.
I did not put the emulator through too many paces. I did notice that the graphic keys are supported (the grey characters). If you looked at only the screen you would swear it was really a ZX81. It looks that good.
Since some of the example programs are Machine Code, I would assume that the emulator supports the full memory map of the ZX81. You should be safe doing assembly language programming with it.
There is no mention of how to get existing ZX81 programs to the ST. Some sort of modem transfer might work.
The final thing about the emulator is that it is freeware. Since the ZX81 ROM is still technically copyrighted by Sinclair Research Ltd, if you own a ZX81 or a T/S 1000, you should be OK legally. But I doubt that the copyright of the ZX81 ROMs is being seriously upheld. If there are any Sinclair people out there that don’t have a ZX81 or T/S 1000 (which I doubt), there are lots of them at flea markets for about $10 or less.
As for the Atari side, I have an old 520 ST with an old Single Sided, Quad Density disk drive and it works find on this. It should work on any ST, STE, MegaST, etc.
In summary, if you have an ST, pick up the emulator, It’s free and kind of fun to have.
There might even be somebody out there using any of the ZX81 emulators for serious work. If you love the ZX81 and want to continue using it and do not want to worry about your ZX81 dying, the current emulators are good enough to replace the old hardware.