|1977 Commodore PET 2001-8|
The rumor on the street is that most (all?) of those PETs were beyond repair. Fortunately this one didn't need a whole lot. It needed a new fuse and fuse assembly. I borrowed one from the non-functional units. It also needed a new monitor, so I swapped monitors with another unit as well. It needed a new belt for the cassette recorder, and just a lot of TLC in general. For example, its overall condition was really dirty and nasty -- like everything in that warehouse. It must have been there for over 30 years. It needed to be completely taken apart and cleaned. It also really needed a fresh paint job. It got all of that and more.
|1978 HUH PET Beeper|
The Pet Beeper was a cool idea. Since it took so long to load programs from cassette, it would beep and inform you that your program was finished loading. That way you were free to focus your attention on other activities while waiting.
It wedged itself between the motherboard and the cable running to the cassette recorder. It had a little clip for a speaker and a tone control as shown (in blue). No software was required since it would just monitor the signals directly from the tape. It would beep once on the header when finding your program, and once again at the end of program load.
The units sold with a one page instruction leaflet. It explained how you could make the unit beep under program control. One thing I found was interesting is that once the unit was told to beep, control was immediately returned to the CPU for the duration of the beep. One could not control the length of the beep or tone in software. These changes could only be made by adjusting the hardware.
The Pet Beeper can be used with any Commodore computer up through the 128 as long as it has the same kind of connector (or adapter). Since the Commodore cassette firmware only communicated at a mere 300 baud (0.000003 megabits per second), the Pet Beeper was a very neat idea for its time.
|1978 HUH Petunia|
I am struck by how rich the Petunia sounds. Much more like an organ than the Commodore 64's SID chip or the Nintendo NES -- both of which would follow several years later.
It came with a much more complete manual that explained all about this fascinating device. Clever programmers could even play software tricks to make it sound like a human voice. Once such game was PET Tetris v1.3 by Tim Howe in 2010. (Archive includes 3 variations, including DAC.) It says the Homer Simpson, "Doa!," phrase when you lose. There are some additional effects, too, like a friendly, "bubble pop," sound when you clear a row.
|InfoWorld - May 25, 1981|
Like many other microcomputers of the time, the PET was not originally designed to produce sound. As shown already, a few methods of sound generation were possible. The most popular one employed the use of the CB2 line on the PET's Versatile Interface Adapter (MOS 6522) chip. It is exposed on the parallel user port on pin K, as shown below. Users discovered that it could be used to generate a 'square wave' output by setting a 'handshake register' into a free-running mode. By adjusting the pattern of output and the frequency, one could produce a wide variety of sounds and music. Approximately three octaves of notes and various noises could be achieved with its one voice output. Several games took advantage of this hack, like Space Invaders.
|Use of CB2 and GROUND for sound output.|
|2716 to 6540 ROM adapter|
|composite video adapter|
|PETdisk on the IEEE-488 bus|
|some files on the SD card|
On the outside of the case, as was common in the day, I placed a toggle switch and two momentary switches. The toggle switch on the bottom of the small, black, project box flips between BASIC v2 and BASIC v4. The momentary switch on the side resets the computer to its power-on state, and the momentary switch on top can be held down while resetting to force the computer into the machine language monitor. A special key sequence, discovered by Jim Butterfield, could be entered into the MLM to recover RAM after a crash.
|homemade switch box for PET|
For more information you can research the following resources:
I have additional PET/CBM material over on my web site: http://www.geocities.ws/cbm
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