PET 2001

Right. Lets hope my mail software (Lotus Cack-Mail) doesn't crash just as I get near the end of this reply, as it did last time. First, all concerned should glance at Larry A's PET faq, the address of which he posted a few messages ago. Pete Turnbull wrote: I agree with Pete, not that it makes much difference. No. Never. 12 inch screen on 4032 (or possibly 4016) and above only. First PETS: 2001-4 and 2001-8 (also called 4k PET and 8k PET). Blue trim, blue-white phosphor, mangled and rebadged cassette (I can't remember whose) that you open by lifting the lid. Then: 2001-4 and 2001-8 get Black trim and C2N cassette deck Then: Green screen. Next was the ROM upgrade. Usual models were 2001-8N, 2001-16N, 2001-32N, 2001-8B, 2001-16B and 2001-32B. These had full-sized keyboards and external C2N decks. In the UK, 2001-8N with tiny keyboard and built in C2N was common. This was not a new motherboard in an old case - the case was a different shape (slightly less tall). Larry has suggested that these might be the 2001-8K, K standing for Calculator (-style keyboard) (sic). All of these had small screens. I've never heard of 2001NT. AFAIK, N = Non business keyboard. The top row of keys was !"#$%^&'() like the tiny keyboard machines - numbers were only on the number pad. B = Business keyboard. Top row of keys was 1234567890, shift gave you !"# etc. This meant you couldn't get some of the "graphics" characters that came from shift-! etc. Hence the reference to "Num. Keys" above. Strange. Full size keyboard with graphics symbols should be 2001-8N Nor do I. All 2001 PETs had 9 inch screens. Are you sure? I thought the 2001-8N and 2001-8B got renamed 3008 a bit later. Um. The first with the 12 inch screen was the 8032. Different firmware and re-done video circuitry. Later some of that was put into 4032, making the "fat 40" Bank switched RAM made an 8096... Was it? That's weird! Even weirder, though, was the lower case implementation. Take a couple of steps back and get a wider view: PET had two internal character codes. Screen codes and "ASCII". Screen codes went from 0 to 127, and didn't include control codes; they then went from 128 to 255 in "reverse field" (inverse video). Bit 6 (the 64s bit) told you whether it was a shifted character or not. 0 to 31 were @, ABC...Z, [\], up arrow, left arrow. 32 to 63 were conventional ASCII. 64 to 127 were the graphics characters you got from shifting these. First problem - nowhere for lower case. PET, in translating ASCII (or PETSCII as it became known) into screen codes, didn't bother to implement lower case. First it checked for control codes (0 to 31 and 128 to 159) and then it ANDed the ASCII code with 63 and stuck it on the screen. Well, sort of. The ASCII codes for the shifted characters were displaced from the unshifted ones by 128 instead of 64. Now, lower case mode. Early PETs kept the bottom 128 ASCII codes exactly as they were. Lower case went in the top 128 - NOT where you'd conventionally put it (those who followed the algorithm above will have worked out that the conventional ASCII codes for lower case would display space, !"#$ etc.). Since lower case was implemented in the character generator only - an I/O pin went to an address line on the character ROM - you had to use SHIFT to get LOWER case. And that was the second problem. Later PETS swapped lower and upper case letters. So now ASCII codes 65 and up, which still mapped onto screen codes 1 and up, gave LOWER case letters, but you pressed SHIFT for upper case. However the OS and BASIC (one and the same, really) treated unshifted as letters, and shifted as meaningless graphics characters, whichever mode you were in. Confused? It is, isn't it! The common arrangement. But the colour change predated the ROM and Keyboard Size changes. Just. aka GPIB, HPIB IEEE-488 to RS232 converters were very popular here, since PET had no serial port. Alternatively, software could be written to drive a pin on the user port serially. I know. I've done it. "Don't support a disk drive" is a euphemism for so many bugs you can't use it at all! About then. The monitor - hex only - replaced diagnostic routines in the original ROMs. A listing was actually given in the original PET manual, but I couldn't get it to work whenever I typed it in... It says "COMMODORE BASIC 4.0" but I can't remember whether between *** or ###. Indeed. Type WAIT 6502,100 I have heard all sorts of numbering schemes for BASIC versions. The only thing they agree on is 4. AFAIK, the BASIC in 3008 and friends was identical to the upgrade ROMs that went in original PETs. That clears up my mystery above. Thank you. Wrong, I'm afraid. POKE 59468, 12 (UC/graphics) and POKE 59486,14 (LC) are INDEPENDENT of ROM version. On 8032/8096, 8296 and Fat 40 you can use PRINT CHR$(14) and PRINT CHR$(142) (CTRL-N and CTRL-SHIFT-N except that PET never had a control key) to change between the modes. These codes also change to wide line spacing in LC mode, which the pokes don't. Hope this clears up some misconceptions. Philip.