Classic Computer Magazine Archive COMPUTE! ISSUE 1 / FALL 1979 / PAGE 87



Model 15-A $99.95
$149.95 with BASIC Programmer's Toolkit

Small System Services, Inc.
900 Spring Garden St.
Greensboro, NC 27403

Like many early purchasers of the Commodore PET, I looked forward to the introduction of the normal sized keyboard 16 and 32K models. When one arrived locally, the first entry I made was a SYS(64824) call which on the old PET's initializes the operating system and prints out the free memory. I was surprised when this crashed the system. After recovering by turning the 16K PET off and on, I PEEKed location 135 and found that this location couldn't possibly contain the upper limit of memory (for a 16K PET this should be 64 and it was something like 255). Then I looked at the manual and discovered that a drastic revision of key memory locations occurred in the process of getting the "bugs" out of the old operating system. In as much as many programs I had developed since 1976 depend on calls to the operating system, I was upset to say the least.

As I'm sure is the case with many, I have learned to live with the bugs in the original PET BASIC and have developed many programs within its not too serious limitations. While most simple — all BASIC — programs will run on either version of the PET, many assembly language programs will run into trouble (for example, unused page 0 locations on the old PETs may be used on the new ones and using these locations for temporary storage can bomb the system). The only near saving grace was that the manual accompanying the new PETs did have a reasonable memory map (it took a year and six months to get the equivalent from Commodore for my old PET but fortunately other owners beat that record) so there was hope of revising my operating system software to be compatible with the new machines. But could I count on new software to be compatible with my old PET? Should I order the new ROM's and take advantage of the fixed bugs and the ROM monitor? But then my high memory monitor (which includes a dissassembler) wouldn't work. would new peripherals from Commodore (especially IEEE ones) work with the old ROM's? I soon found my word processing program would not work with the new ROM. These were some of the many questions that crossed my mind. The BASIC SWITCH is the solution for being able to use either the old or new ROM's without having to do any more than throw a switch. The change can be made without turning off the PET and the system is re-initialized by the process, i.e. "### COMMODORE BASIC ###" or "*** COMMODORE BASIC ***" and "XXXX BYTES FREE" are printed out depending on which set of ROM's you have just switched in. This device does not tie up any of the ports so if you have peripherals like the CGRS PEDISK or the BETSI, you can still use them. As and added extra, the SWITCH has an empty socket for EPROM. I have seen the SWITCH in operation with a BASIC PROGRAMMERS TOOL KIT (Palo Alto IC's, A Division of Nestar Systems, Inc.). The empty socket is a zero force insertion socket so other ROM's can easily be substituted (finally the flexibility of a plug in ROM!). Although the Tool Kit has been reviewed elsewhere, I can add my enthusiasm for this product after having seen it in action. The 15th ROM socket can be readdressed in the area reserved for ROM expansion in the old PET's (starting at $B000) in order to avoid conflict with other additional ROM's (for example the DOS boot in ROM for the CGRS PEDISK is addressed starting at $B000).

In, summary, the BASIC SWITCH offers old PET owners the advantages of the new ROM's while at the same time avoiding the time consuming process of rewriting existing operating system dependent software. As an added bonus, ROM-packs like the BASIC Programmer's Tool Kit (and hopefully others in the future) can be used.

Dr. J. A. Dilts
Department of Chemistry
University of North Carolina at Greensboro
Greensboro, NC 27412