Readers' Feedback

The Editors and Readers of COMPUTE!

If you have any questions, comments, or suggestions you would like to see addressed in this column, write to "Readers' Feedback," COMPUTE!, P.O. Box 5406, Greensboro, NC 27403. Due to the volume of mail we receive, we regret that we cannot provide personal answers to technical questions.

Forward Two Steps, Back One

Rumors abound that the Amiga is or can be compatible with the Commodore 64. If it were, I would buy one without hestitation.

William F. DeBerg

I maintain a very firm belief that Atari should market an Atari 8-bit emulator for the ST.

Damon Milhem

Can I expand my VIC to run 64, 128, Amiga, or Atari ST programs?

Jeffrey M. Powers

Judging by the letters we receive, and by the questions and comments in the user group newsletters that we read, there is a great deal of interest in emulation—making one computer run programs written for another.

Emulation is a complex subject, so let's begin with a simple question that was popular a few years ago: Why can't my 64 run VIC programs? (Some people asked the opposite question: Why can't my VIC run 64 programs?) They continue by saying that the two computers look similar, use the same peripherals, and were made by the same company.

Although there are many differences between the two computers, the major difference lies deep within the computers themselves: They have different display hardware. The VIC used a video chip called the VIC; the 64 used a chip called the VIC-II. For a program to work on two computers, it must "see" the same hardware registers in the same memory locations.

With the popularity of the Amiga and the Atari ST, the question is coming up again: Why can't my new computer run my old programs? And, again, the alternate question: What can I add to my old computer to gain the benefits of the new?

Adding components to your old computer to gain the speed and graphics capabilities of the new computers is simply not feasible. To add the features of the Amiga to your 64, for example, you would have to replace the microprocessor, keyboard, RGB output, and sound and graphics chips. Indeed, a 64 has almost nothing that an Amiga could use. In essence, you would have to add a whole Amiga to your 64.

Others want their old software to run on their new computer. This approach is only slightly more promising. Programmers are working on an Atari 8-bit emulator for the ST and a Commodore 64 emulator for the Amiga. Unfortunately, this approach is bound to lead to lackluster results. The 16-bit 68000 microprocessor used in the ST and Amiga is simply not fast enough to emulate eight-bit computers at full speed. Although the 6502 is reasonably easy to emulate, duplicating the hardware of the the still-impressive 64 and Atari eight-bit computers would be a monumental task. The emulators we've seen achieve approximately 20–30 percent of the speed of the original computer. Even if you had perfect emulation, you would still need to transfer your programs across incompatible disk formats, or from program cartridges.

The best solution to the problem is this: If you want to run programs written for a specific computer, or if you want to write programs to take advantage of the power of a certain computer, buy that computer. Any other option will lead to frustration.