By Editors & Readers — originally published in COMPUTE!’s Gazette Issue 2, August 1983
Off-Center Screen
Here’s my question: Where are the memory locations on the Commodore 64 to center the screen? For the VIC, the locations are on the VIC chip at 36864 and 36865. Have I overlooked something somewhere? I would appreciate it if you could answer my question for myself and other readers who might be wondering the same thing.
John Van Winkle
As you mentioned, the VIC chip (which controls the video output in the VIC-20) has the ability to adjust the horizontal and vertical positioning of the screen. Unfortunately, this ability to center the screen display on your monitor or TV is not available on the VIC II chip, which controls the video output on the Commodore 64. There are locations that can be POKEd to adjust the positioning of the output on the screen (53265, 53270), but these locations are not the answer to your problem. While the print characters are moved, the screen is left behind.
Mystery Keys
After looking through the Commodore 64 Programmer’s Reference Guide several times, I still have no idea how to assign functions to the four keys to the right of the keyboard (F-keys). Could you give an example of this? Also, is it simply a matter of POKEing a location? How does one find out what those precise locations are? Any help will be appreciated.
J. W. Hewitt
The easiest way to assign functions in a program to the special function keys is via the GET statement in BASIC. This can be accomplished with an IF-THEN statement in the same way you would for any other key on the keyboard. Enter the following short program on your VIC or 64 for an example:
Watch future issues of COMPUTE!’s Gazette for full-length articles which will describe in detail how to program the special function keys on both the VIC-20 and Commodore 64.
Which Monitor?
I would like information on monitors for my computer. I own a VIC-20, but haven’t seen information on what monitors are on the market and best-suited to buy. Maybe an article put together by this magazine to show what is out there would help me and others decide what to buy. Any information would help.
Maurice H. Albaugh
There are many monitors and TV sets on the market (both black and white and color) that are suitable for use with your computer. Commodore recently introduced a color monitor that is especially designed for use with the 64. The suggested retail price for this monitor is $299.95. If you can wait a few months, COMPUTE!’s Gazette is planning an article similar to the one you suggested.
Disk Drive Conversion
I own a VIC-20 with a 1540 disk drive. I and a few of my friends are thinking about buying the Commodore 64. While considering the differences between the 1540 and 1541 disk drives, it has been rumored that the 1540 can be changed to a 1541 by replacing a ROM chip. My problem is in trying to find someone or a store that can replace this chip for me. Do I have to bring it to a Commodore dealer or is it a simple replacement that can be done at home?
David Leung
It’s true that a 1540 can be converted into a 1541 by changing one Read Only Memory (ROM) chip. Check with your local Commodore dealer to see when this chip will become available. After conversion, the drive will still work with VIC. As general rule, any hardware modification? to
be performed upon any computer or peripheral (such as disk drive) should be performed by an authorized technician. Performing “home modifications” may damage your unit and void your warranty at the same time. To see how you can use your 1540 disk drive successfully with your Commodore 64, refer to “Power BASIC: Using 1540 Disk Drive And Commodore 64” elsewhere in this issue.
Dual Drive Lock-Up
I have recently purchased one of the new Commodore 64 computers and so far am very pleased with its performance. also purchased second
disk drive (both are VIC-154 Is), and if go by the directions in the disk drive manual, and turn my computer on last, the serial bus gets hung up.
I have conferred with other Commodore owners, and they also have experienced this same problem. My question is: Does it really hurt to turn on the disk drives after the computer, and do you know if Commodore expects to remedy this situation?
William Davies
Although it is always good idea to follow the manufacturer’s instructions and turn on your computer last, this is probably not the cause of your problem. All disk drives default to the same device number (#8 for the 1541) upon power-up. What is happening is that at power-up the computer is sensing two disk drives on the serial bus with the same device number (8), thus confusing the computer. The answer to your question can be found near the back of your VIC-1541 User’s Manual. To operate two or more disk drives on the 64 at the same time (the 64 can handle up to five), each drive must be assigned different device number. This can be accomplished via software (programming) each
time you power up, or by hardware modifications, which will make the device number assignments permanent. Instructions for both methods can be found in your 1541 manual.
Standard Recorders OK?
Can standard tape cassette machine be used with the VIC-20 and the Commodore 64, or must purchase the C2N cassette from Commodore?
Eimer Aydelotle
There are few adapters and interfaces made by independent companies which enable you to use standard cassette decks with your VIC or Commodore 64. Watch the News Products section of this magazine for announcements. COMPUTE!’s Gazette may review some of these products also. For more information on this subject, see “Does Your Computer Need Cassette Recorder?” in the July 1983 issue.
Jumping Screens
When connecting my VIC-20 to my Zenith System III TV, know how to POKE 36864,133 to keep the screen from jumping. However, when using
cartridge, have no control over the VIC-20. The instructions with the cartridge caution the user about putting in or taking nut the cartridge
while the computer is on. How do prevent the screen from jumping when using cartridge?
Mitchell Bers
If the cartridge instructions do not mention an option for stopping the screen from jumping, then you can’t. Usually, when you plug in game or any other cartridge, control of the keyboard (and the computer) is handled by the cartridge. “Freezing up” the keyboard is one of the means that programmers use to protect their programs from being copied. A well-written program will include options for adjusting the screen. For instance, the instructions may read, “Press F-l to change screen/border colors.” Many VIC-20 games let you center the screen on your TV. In this case, you just “push” the screen (usually with cursor keys or joystick) completely off the left side of the screen until it wraps around and reappears from the right.
Cartridge Compatibility
Will the VIC-20 Programmer’s Aid cartridge work on the Commodore 64?
John Auresto
No, it will not. The cartridge ports on the VIC-20 and the Commodore 64 are different sizes. Your Programmer’s Aid cartridge will not physically fit into the Commodore 64, and a C64 cartridge will not fit into the VIC-20. Even if you could, the cartridge is still written specifically for the VIC-20. It’s like running BASIC program written for the VIC-20 on your 64. The screen width is different, and all the “memory locations” have moved. There has been talk of third-party adapters becoming available in the future, but us of this writing, we know of nothing available to consumers.