Bally Alley

Michigan Bally Users' Group gets a look at
Zgrass-32 "add-under" for the Arcade!

by George Moses and Brett Bilbrey

(April 1981)

This article is a follow-up to a piece by George Moses called "Michigan Bally Users' Group Report" in ARCADIAN 3, no. 1 (Nov. 6, 1980): 2-3. This follow-up article first appeared in the "Arcadian" newsletter for the Bally Arcade / Astrocade in the April 1981 issue. The four pictures in the newsletter were at least third-generation photocopies, which made the quality poor. These images have been rescanned from the original halftone photographs (from the Bob Fabris Collection) that George Moses provided with his submitted article. Clicking on each picture in the article will display high-resolution scans that have a photo description beneath them. The thumbnail image of the article links to the original 10-page "Arcadian" newsletter.

Michigan Bally Users' Group gets a look at Zgrass-32 'add-under' for the Arcade!

For about a month we had been sending out letters to members of the Michigan B.U.G. and interested parties in neighboring states that it was time for another users' group meeting. The last one had been in October and Astrovision had sent two representatives to answer questions about their takeover of Bally's Consumer Division and to show off some of their forthcoming game cartridges. You read all about it and saw the photos in the November issue of Arcadian. For this meeting, scheduled for February 8, Dave Nutting Associates, designers of the Bally Arcade and the new Zgrass-32 had promised to send a representative out from Chicago with their amazing new computer.

News like this brings all the Bally Arcade owners out of the woodwork! The phone rang steadily for two weeks before the meeting. People had new hope. Some had purchased other computers as they tired of waiting for Bally to keep their promise to expand the Arcade. But these were the people who were most excited about this meeting! And they promised to come by the carload.

Saturday morning, February 7, the day before the meeting we went to Detroit Metro Airport and picked up Craig Anderson from Minnesota and Steve Wilson from Ohio. They came the farthest to attend. At 6 pm that evening the George Moses household was abuzz with a crowd of friends showing off software. Craig Anderson, Brett Bilbrey and Steve Wilson were doing some unimaginable things to the Arcade on George's dining room table when the doorbell rang. It was Scot Norris from Dave Nutting Associates with his wife, Cheryl looking a bit tired after a 6 hour drive. We opened the hatchback of his car and there among the luggage was the Zgrass-32. Tired or not Scot couldn't wait to plug it in and give us a little demonstration of Zgrass before dinner. He had only had a week of working with this computer prior to the meeting and wasn't fully versed in the new Zgrass language yet, but Scot was able to show us some amazing graphics on our TV screen.

CRAIG ANDERSON demonstrates the lite pen he researched and built. It works amazingly well, and Brett Bilbrey wrote some software to boot the Arcade into a high-speed mode to read the data as fast as the lite pen can supply it.

Scot showed us how macros work and demonstrated the hierarchy of the Zgrass language. A macro is a program or subroutine that can run concurrently with other subroutines. The Zgrass-32 can run 127 macros at once. This is called "multi-tasking". You can call any macro, all 127 macros at once, or macros can be programmed to call each other. When you get the program running the way you want it to you can tell the computer to compile it. That is, it will rewrite the program in machine language, thus eliminating the need for the computer to interpret each command before executing it. This results in an amazing increase in speed of operation. He then demonstrated the way the Zgrass-32 can display 4 colors at once with a concentric box routine that when compiled gave a color show that had a tendency to leave one breathless. With this computer you have more screen area as no area is needed at the bottom for scratchpad. You have 102 pixels of vertical display and 160 pixels horizontally with 2 bits assigned per pixel for memory. This is the same as Bally Basic resolution except that the full 4K of memory is used for dynamic screen RAM. The entire ROM inside the Arcade is ignored and the Zgrass-32 uses its own scratchpad RAM within the keyboard so you don't need to borrow any screen RAM. Scot showed how interrupts could be used for updating graphics for smooth animation. Brett Bilbrey recently showed us this is possible with the present Arcade using machine language programming techniques he and Dave Ibach pioneered, but with this new computer it's so easy it's a snap!

Speaking of SNAP, that's the name of a new command you get with the Zgrass-32. Here you can snap an area of the screen display and store it in memory and display that image wherever and whenever you call it. You can write 6 macros that store 6 pictures of a gunfighter walking, for instance. Using multi-tasking you could display them in sequence for the visual display of an animated figure. You can also tie any figure or SNAPped image to the hand control and make it move at your command.

The self-help routine was demonstrated. If you're not sure about the format of a command you just type in the name of the command and the word "HELP" and the computer will ask you for the parameters required so you don't have to grab for the instruction manual each time you begin to use an unfamiliar command. The production line prototype Zgrass units hadn't been built yet, so what we saw was still in the lab-development state. The finished prototype will have BOX, LINE, CIRCLE and POINT commands. Not many computers can draw graphics as fast or as easily as the already existing Bally Arcade. And the Zgrass-32 puts it far ahead of the rest.

Picture 2 - THE SUPPORT given the Michigan B.U.G. by Ron Pollock of Tri-County Electronics in Fenton, Michigan is evidenced here. He opens the entire mall corridor and lines both walls with multi-level counters, supplies dozen of color TVs, power cords and keeps a large stock of Arcades and accessories handy for everybody.

The cassette tape interface is built into the computer and runs at 2000 baud. It differs from the interface we have now in that it is not a wave scanner. All it looks for is sound wave peaks and could care less what shape they're in. So it's a bit more forgiving than what we've had to tolerate in the past. The interface seemed to write more reliably to tape when the jack was plugged into the auxiliary plug than when using the mike plug.

Two RS232 ports will communicate with disc drives and printers. One thing we'd like to see is a parallel printer port that would handle a standard Centronics printer. The more expandability it has the more saleable the computer will be. The character set needs some refinement from what we saw and comments we heard at the meeting. The 3x5 pixel characters in low resolution provide 40 characters by 24 lines. Most people remarked that they would like to see higher resolution. As we remarked earlier, this was a lab-development model. More bells and whistles will be added by the time the assembly line gets cranked up. E.F. Johnson, the electronics firm in Garner Iowa, is said to be gearing up for prototype production.

Picture 3 - THEY'RE HIGH ON ZGRASS - Kim Moses, George Moses (her dad), Brett Bilbrey, the Zgrass-32 Computer, Scot Norris, Dave Ibach and Craig Anderson.

The advantages of Zgrass, a graphics language, is that the graphics handling is done by a language that was created for just that purpose. Commands for screen manipulation have been tied in with screen interrupts and display techniques so they're executed much faster and more efficiently than any TRS-80, Apple or Atari could ever hope to do. The add-under will access the custom chips in the Bally Arcade, which will facilitate moving graphics commands thru the Z80 microprocessor. Just as the Bally originally was accessible to "hacking" once we figured everything out, it looks like the Zgrass-32 will have the same ability with as many expansion peripherals attachable as possible. For instance, a parallel port, a serial port, expansion port, disc connector, and dual cassette controllers. The same foresight appears in this design that was in the Arcade's 50 pin expansion connector.

We also got a look at the science math package, a software feature that's built-in and is not common in any other computer, featuring 13 digit accuracy. Scot demonstrated the sine and cosine features and drew several concentric circles for us. The Screen Editor allows you to use the joystick to move the cursor anywhere on the screen and use the knob and trigger to insert spaces or remove characters. You can do the same thing with the keyboard using left-right and up-down arrows and you can type in corrections directly over the errors. With many computers you have to go looking for a program using addresses to find macros or information off a disc. You have to direct the flow. But the Zgrass-32 maintains all internal control to save any macros or variables on tape or disc for you in one clean sweep. In other words, it does all your housecleaning for you. The computer already has the software built-in to handle multiple program storage and variable allocation with just a simple command.

Picture 4 - THE CIRCLE drawing function is shown here. Also notice the self-help 'PROMPT' function of the Zgrass-32. You can see some of the 3x5 character set displayed in this photo.

Zgrass in no way resembles Basic. It uses no line numbers. It's easy to learn. And it will write better programs for the person who wants to see the program come alive visually rather than just print text. Basic was written to teach programming to computer students. Zgrass was developed from the start to do computer graphics. You get it as standard equipment in the Zgrass-32 for only $599.00, plus the price of your Bally Arcade that must rest on top of it ($299.00). Everybody was amazed at what it would do for its total cost of $898.00 (both modules together). When you compare this machine with its 32K RAM and 24K ROM with a 16K Apple II Plus that runs $1,195.00, it seems like a bargain. As the software appears on the market to make the Zgrass-32 do the things it was designed for, our impression is that it'll be an item in high demand at your local computer store.

This article is a follow-up to an article by George Moses called "Michigan Bally Users' Group Report" in:

     ARCADIAN 3, no. 1 (Nov. 6, 1980): 2-3.

Return to Bally Arcade / Astrocade Articles and News