Preliminary PET FAQ

I figured I'd shoot this by you guys as I am getting closer to putting it on my web site. I am sure I will get some good criticism from you all. If you have any additions/suggestions or additional questions to include, let me know. I also plan also to add in a couple texts on disk drive usage some PET memory maps (gee there are barely any PET maps on the net!) and if I don't find a link to one, an overview of Commodore PET BASIC (applies to 64 also). (view with a monospaced font for best results) THE COMMODORE PET COMPUTER FREQUENTLY ASKED QUESTIONS FILE - VERSION 1.0beta --------------------------------------------- BY LARRY ANDERSSON, COMMODORE COLLECTOR AND PET ENTHUSIAST --------------------------------------------- WHAT MODELS OF THE PET ARE THERE? The PET line was Commodore's first computer line after purchasing MOS Technologies the primary design of the computer (as well as its microprocessor, the 6502) was by Chuck Peddle. The line was labeled in series' the first series, the 2001 series, the european 3000 series, and the modern 4000 and 8000 series, and the final single unit 9000 series which is the SuperPET. 9" display units (40 column x 25 line character only display): PET 2001series: Original PET: - Steel case - Internal 'datasette' cassette tape drive - Blue on black 9" display - Small 'calculator style' keyboard - Small shipment with 4k, most with 8k RAM - Original ROMs Large Keyboard PETs (no more internal datasette drive): PET 2001 xN (x=8,16,or 32 depending on amount or RAM it was shipped with) - Full-size key keyboard w/PET graphic symbols imprinted on keys - Upgrade ROMs - Many steel cased, some w/molded plastic tops. - many with clearer green on black displays - Later versions had 4.0 ROMs installed PET 2001 xB (labeled as CBM, Commodore Business Machine) - Full size xx key keyboard (no graphics symbols printed on keys) - Upgrade ROMs (powers up in upper/lower case mode) - Later versions had 4.0 ROMs installed - Many w/molded plastic tops some steel cased. PET/CBM 40xx Series (PET= N keyboard/ROM, CBM= B keyboard/ROM, xx= RAM) - 4.0 ROMs - molded plastic top 12" displays - updated video controller (prone to the 'killer poke') - internal piezo speaker, audible startup, and right margin sound. - 4.0 ROMs PET/CBM 40xx (PET= N keyboard/ROM, CBM= B keyboard/ROM, xx= RAM) - 40 x 25 display, upgradable to 80 columns - lower case availabe by CHR$(14) which also changes line spacing. 80 column series (can be set to 40 column mode via software.) CBM 80xx - 80 x 25 display, powers-up in upper/lower case. - buisness xx key keyboard - later versions had 64k & 96k RAM expansion board options. - 4.0 ROMs PET SP9000 SuperPET (or Micro Mainframe) - 80 x 25 display - 6809 co-processor board - 96k RAM - True RS-232 interface - Multiple charactersets (for APL, etc.) - Avalability of disk Based languages MOTHERBOARD SERIES 2000 series(9" CRT) 3000 & 4000 series (8" CRT) IEEE user tape #2 IEEE user tape #1 +------####-####--##-+ +------####-####--##-+ ! # ! #! ! # ! #! ! # exp ! #! exp ! # bus ! ROMS #! bus ! # ! F E D C A B 9 #! ! # ! #! ! ! ! ! ! ! ! ! ! ROMS ! ! ! ! F E D C A B 9 ! ! ! ! ! ! ! tape # RAM MEMORY ! tape # RAM MEMORY ! #1 # ! #2 # ! +--------------------+ +--------------------+ 4000/8000 series (12" CRT) IEEE user tape #1 +------####-####--##-+ ! # # tape ! # # #2 ! R exp bus # ! ! A #! 2000 Series ! M 9 #! circa 1977/78 Max RAM - 8k ! A #! [daughterboard exp to 32k] ! M R B ! ! E O C ! 3000 & 4000 Series ! M M D ! circa 1979/80 Max RAM - 32k ! O S E ! ! R F ! 4000 & 8000 Series ! Y ! circa 1981 Max RAM - 32k* ! spkr! [daughterboard exp to 96k] +--------------------+ WHAT VERSION OF ROMS DO I HAVE ON MY PET? The PET/CBM line had three major ROM revisions as well as a few minor ones, you cannot reliably determine the ROMs by looking at the outside of the PET (unless it has a large monitor). Fortunately there is an easy way to distinguish the three various versions by just turning on the computer. Depending on how your start-up message looks you can determine the ROM version: *** COMMODORE BASIC *** - Original ROMs sometimes referred to as 2.0* ROMs. (only found in the older calculator keyboard style PETs) Occupy $C000-$FFFF ### COMMODORE BASIC ### - Commonly known as the 'Upgrade ROMs' sometimes referred to as 2.0 or 3.0 ROMs depending on who you ask. Occupy $C000-$FFFF *** COMMODORE BASIC 4.0 *** - 4.0 ROMs The only ROMs that will work on large-screen PETs. Occupy $B000-$FFFF * Some people contend that BASIC version 1.0 never made it out of beta development and the PET line started with version 2.0 ROMs... Commodore on the other hand usually refers to the 'Upgrade ROMs' as V2, or 2.0. For the sake of sanity in this FAQ I will refer to them as original and upgrade ROMs, and as for an opinion I will go with the company's numbering (which leaves V 3.0 out of the picture). WHAT ARE THE DIFFERENCES AND/OR BUGS OF MY VERSION OF BASIC? Original ROMs Commodore had not yet implemented the IEEE-488 disk routines. Arrays are limited to 256 elements due to a bug in firmware. There is no machine language monitor nor could the PEEK command access locations above memory location 49152. The upper/lower case character set was inverted (SHIFT for lower case) (note: reading my sources there are ALOT of bugs, will take a while to compile them) Upgrade ROMs Many Original ROM bugs were squashed. BASIC commands and capabilities very much like the Commodore 64's. Now includes a tiny ML monitor and IEEE-488 disk operability. Easter Egg - enter WAIT 6502,x to see MICROSOFT!' displayed on the screen x number of times. 4.0 ROMs* Addition of direct Disk operation commands DLOAD, DSAVE, COPY, HEADER, etc. Ability to repeat cursor control characters by holding down keys. Reserved DOS error-channel variables: DS,DS$. Added screen 'window' formatting control characters. * The small screen-and large screen versions of these ROMs differ and some software developed for the small-screen 4.0 ROMS crash on the large screen units. This is due to the necessary changes made for the new video controller of the 12" display PETs. CAN I RUN VIC-20, 64, 128, PLUS/4, OR C-16 SOFTWARE ON MY PET? Maybe. Any program that is all BASIC that does not use hi-res graphics or sound and contains no POKES should work readily on a PET. Of course if it contains POKEs, sound commands, and Machine Language conversion will be nessasary. If it rely on more than one voice of sound, hi-res grpahics, programmable character sets or color, it may not be worth converting because those features aren't present on the PETs. NOTE: Many early VIC, 64, and Plus/4 BASIC games and programs were converted PET games. HOW DO I GET 64 (VIC, PLUS/4, ETC.) BASIC PROGRAMS ON MY PET? Unlike the later 8-bit Commodores,the PET always loads programs into the memory address they were saved at (i.e. no loading ,8 and ,8,1 as on the later machines), which means BASIC programs saved on VICs, 64s, 128s, etc, will not load in the right location on the PET to be seen by the BASIC interpreter. PET BASIC starts at location 1025 ($0401 in hex) and the later Commodore machines have different, higher starting locations. (see table x) There are a couple ways to get a BASIC program to load properly into memory, Disk Track/Sector Editors: My preferred method of conversion is using a disk track/sector editing utility to change the 'load address bytes' of the file directly on the disk. This is not an easy process to 'explain' and I hope to write it up at a later time. BASIC Line Relocation Method: Here is a way to get the BASIC editor to do it for you; of course you will need to have an upgrade ROM or later PET (which has a ML monitor) or load in a monitor for your original ROM PET first. It involves 'linking' the higher located BASIC program to a line starting in regular BASIC, when you delete that line, the editor will move your program to where it belongs in memory. 1. Enter NEW to erase any programs already in memory. 2. Enter: 0 REM 3. LOAD the program you want converted (i.e. LOAD"program name",1 for tape) 4. When loaded, enter the machine language monitor by entering SYS 1024 5. display the first part of the BASIC you first typed: M 0401 0408 6. Change the line-link to the memory location of the program to be moved; use cursor keys to move up and change the first two two-digit numbers to read: :0401 01 08 00 00 8F 00 00 00 ^^ ^^ (for a program from a 64, otherwise, see table x) 7. Press return to change the bytes then enter X to exit the monitor. 8. Type LIST, you should see the 0 REM followed by the program. 9. Enter 0 to delete line 0 which will move the BASIC to its proper place. 10. Save the program. TABLE X - Load Addresses for BASIC files: Saved under Start of BASIC Computer load load change Model/ addr. addr. bytes configuration dec. hex. to: ------------- ---- ----- ----- PET/CBM 1025 $0401 N/A VIC-20 unex. 4097 $1001 01 10 VIC-20 +3k 1025 $0401 N/A VIC-20 8k+ 4609 $1201 01 12 Commodore 64 2049 $0801 01 08 B-128 0003 $0003 * Plus/4-C16 4097 $1001 01 10 Plus/4-C16** 8193 $2001 01 20 C128 mode 7169 $1C01 01 1C C128 mode** 16384 $4001 01 40 * The BASIC RAM of the B128 is located in a separate bank of RAM memory, which starts at a VERY low address and will be difficilt to convert without a track/sector editor or saving it special on a B-128 itself. ** When hi-res GRAPHICS mode space has been allocated. WHAT KIND OF DRIVES CAN I USE? Tape Drives Tape Drives for the VIC, 64 and 128 work well on the PET. In fact you can hook up 2 tape drives on the PET (the second connector is inside the case, on the edge of the motherboard.) and can be accessed as device #2. Commodore Models: SANYO - First drives, power supply section cut out and modified for PET datasette cable/plug. C2N - Box look, black or cream colored case. 1530 - Rounded low-profile, counter & 'save' indicator light. Commodore IEEE-488 5.25" models 2020 - (first drive design, bugs may be present) 2040 - Updated ROMS, resembles a 1541 format & readbable on 1541/71s 4040 - Read/Write compatible with 1541/1571s. 2031 - Read/Write compatible with 1541/1571s. 8050 - Single Sided/Quad Density format, 512k per disk side. 8250 - Double Sided/Quad Density format, 1mb per disk SFD-1001 - Same as 8250, but single drive unit. Commodore IEEE-488 8" 8280 - 1 MB or 512k per Drive (little info on this one...) Commodore IEEE-488 Hard Disk Drives 9060 - Five Magabyte Hard Disk Unit 9090 - Seven Megabyte Hard Disk Unit 3rd party MSD-SD1 ** The MSD SD1&2 offer both IEEE-488 and MSD-SD2 ** VIC/64/128/+4 Serial bus interfaces. Modified 1541 PRINTERS? Commodore Model IEEE-488 Printers 4022 4023 8023 Some companies produced printers with IEEE-488 interface options (Epson was one) HOW CAN I GET PET PROGRAMS FROM DISK TO TAPE? You can just LOAD the program from tape and and SAVE them to disk one after another, of course, if you are using a VIC/64/128, etc. the loading address will get messed up. Fortunately there is a wonderful fily copy utility available for PET (4.0), VIC, and Commodore 64/128, called 'Unicopy'. Unicopy (written by the famous Commodore enthusiast, Jim Butterfield) allows you to copy from disk directly to tape. This of course preserves the loading address and makes things mauch easier. (also it performs multiple file copies instead of just one program at a time). HOW CAN I GET PET TAPE PROGRAMS TO DISK? Again you can do LOAD and SAVE as I mentioned or use a handy little utility I had discovered for the 64. This program will automatically LOAD each file off of tape and subsequently SAVE it to disk and continue until you stop it (or a disk error occurs when it attempts to save a file with the same name as one already on disk, disk full, or end of tape. HOW DO I HEAR/PLAY SOUND ON MY PET? Like many other microcomputers of the time the PET was not originally designed to produce sound. A few methods of sound generation have been developed but the most popular employs the use of parallel user port pin M which generates.... The latest 4000/8000 (large screen PET) motherboards have a built-in piezo speaker and also have a bell sound accessible with a print: chr$(7) Sound Interface Diagrams here... WHAT ARE THE BASIC COMMANDS FOR MY PET? For the most part the BASIC on the 64 is identical to the upgrade ROM PETs and it only varys by a few commands and features between original and 4.0 ROMs. On the other hand the 'memory map', the locations you POKE numbers into, vary quite a bit between ROM revisions. Memory Maps are available for all the versions... HOW DO I ACCESS THE PET's M/L MONITOR? The 'timy machine language monitor' (known as TIM to some) is available on all PETs but the original ROM version. TIM is invoked by executing a BRK instruction by SYSing any memory location containing a zero (0), most people enter SYS 1024, as it almost always contains a 0. WHAT ARE THE COMMANDS FOR THE M/L MONITOR? G - Execute M/L: G programaddress (i.e. G 033C) L - Load: L "filename",dev (i.e. L "PACMAN",08) S - Save: S "filename",dev,startaddress,endaddress (i.e. S "FLASH ATTACK",02,027A,2000) R - Display Processor Registers X - Exit Tiny Mon M - Memory Display: M startaddress endaddress (i.e. M 0400 04A0) : - Modify Memory (supplied in memory dumps using the M command) ; - Modify Processor Registers (supplied in the processor register, P command) CAN I GET A BETTER M/L MONITOR FOR MY PET? Yes, there are two that I know of that are readily avaiable. The most popular (and universal among the Commodore 8-bits) is Jim Butterfield's Supermon. There are versions available for all ROM revisions including original ROM PETS and offer a mini Assembler and Disassembler among other useful memory/ML commands. The other, similar to Supermon is called Extramon. There are other versions many of wich are commercial but I have little information on them. I HAVE A PROGRAM THAT CAN USE JOYSTICKS, WHERE CAN I GET/MAKE THEM? The PET was not initially designed for joysticks but a determined user had devised a dual-joystick interface employing the parallel port. This interface allows you to plug in standard Atari/Commodore compatible joysticks.... Interface Diagram Here HOW COME MY PET CAN'T READ A TAPE FROM MY PLUS/4 OR COMMODORE 16 OR VISA-VERSA? You are quite a collector, aren't you? When Commodore designed the Plus/4 and Commodore 16 they broke alot of standards they had previously established for their 8-bits (and fortunately went back to in the C128); besides the plug designs, they changed the sound-frequency of the signals used to record on tape. Though the the format is identical to the PET and the other 8-bits, the sound is only readable on the Plus/4 and Commodore 16. My sggestion would be to record the program on disk (1541) and then read it on a 4040 or 2031, or copy them from the 1541 to tape using a 64 or 128. WHAT IS THE 'KILLER POKE' AND SHOULD I WORRY ABOUT IT? This is THE POKE of computer lore, the command that WILL physically break a computer! Of course other commands and methods are known that can potentially cause damage (usually to disks, hard drives or other mechanical units), but this is the most notable mainly because it was a command somewhat commonly used and it affects solid-state circuitry. History of 'the killer poke' When the first PETs (small 9" screen) models came out, the display wasnt all that fast. It wasn't too long before someone learned they could impove the character printing speed via a poke to location 59458; which would set the video controller into a faster mode. It was a noticible improvement of speed on programs using PRINT often, it was kind of like a free upgrade. It was mentioned in a few publications and used in many programs that relied on printing to the screen. I had learned of the poke through Cursor Magazine, a monthly tape-based publication. They printed the command in one of the 'newsletter' flyers included with an issue which you could insert into their game "joust" to make it play faster. Later on, when Commodore released the larger display (14") PETs, they had  improved display speed which made that POKE unnecessary. An unfortunate side effect was that the POKE to 59458 still caused the already faster controller to run even faster, in fact too-fast, which could result in damaging the PETs video curcuitry when left running. I discovered it by accident after our school received some large-screen 4016s. When active, the screen starts to warp after about the third line and the display stops around the fifth, the keyboard is also unresponsive. When a PET is in this mode, the only solution is to turn it off, quickly! Fortunately none of the school's PETs were damaged due to this POKE. Later Cursor Magazine published a 'fix' that would allow older PETs to use the poke and keep the large-screen units from frying. Unfortunately there are still many programs that do not have this fix. Prevention Make sure to check BASIC programs (especially games) when running them on a large-screen PET and be ready with the power switch when you first run it. I have usually found the 'killer poke' statement looking like this: POKE 59458,PEEK(59458)OR 32. The fix is to put an if-then conditional to determine if the poke is needed for the PET running the program, here is the code: IF PEEK(50000) THEN POKE 59458,PEEK(59458)OR 32 CAN I HOOK UP AN EXTERNAL MONITOR TO MY PET? With the help of the following circuit you can get a composite singnal from the user port... Insert Video Diagram here.... WHAT ARE THE PINOUTS SO I CAN BUILD AN IEEE-488 CABLE FOR MY PET TO MY DRIVE. WHERE CAN I GET SOFTWARE FOR MY PET? WHERE CAN I GET CONNECTORS THAT FIT THE USER/IEEE-488 PORTS? IS THERE A MODEM AVAILABLE FOR MY PET? I know of only one company that prosuced a modem and IEEE-488 interface, the company is TNW, and I think they also built the Commoodre 8010, an acoustic modem for the PET. I have some notes on using the device but have never actually seen one. Larry Anderson -- -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- Visit our web page at: http://www.goldrush.com/~foxnhare/ Call our BBS (Silicon Realms BBS 300-2400 baud) at: (209) 754-1363 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-