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Looking For Some Advice On My Commodore PET Project ?
- Thread starter SiRSKiNBAD
- Start date
I’ve printed the manuals for everything but not managing to figure it out 
daver2
10k Member
You want to find yourself a good introductory book to the BASIC language (for example https://www.amazon.co.uk/Basic-BASIC-Introduction-Computer-Programming/dp/0810451069).
You should be able to find some books online if you don't want to pay for it.
Ideally, you want to find a book specifically for Commodore PET BASIC - but that is not essential to start with. Try https://archive.org/details/commodorepetbooks to start with.
You want to look at the LET, IF / THEN, FOR / NEXT and PEEK / POKE statements and functions.
If you get stuck, then ask some targeted questions here.
The Commodore manuals are reference material - unless you already know BASIC these will not help...
Dave
You should be able to find some books online if you don't want to pay for it.
Ideally, you want to find a book specifically for Commodore PET BASIC - but that is not essential to start with. Try https://archive.org/details/commodorepetbooks to start with.
You want to look at the LET, IF / THEN, FOR / NEXT and PEEK / POKE statements and functions.
If you get stuck, then ask some targeted questions here.
The Commodore manuals are reference material - unless you already know BASIC these will not help...
Dave
+1 Dave
you want to essentially get the first 8 consecutive values starting at memory address
36864 ($9000)
then the next 8 starting at
40960 ($A000)
then the next starting at
45056 ($B000)
the values will hopefully tell us the memory bank address location of the eprom. Dumping them on an eprom programmer will help us understand what they are
you want to essentially get the first 8 consecutive values starting at memory address
36864 ($9000)
then the next 8 starting at
40960 ($A000)
then the next starting at
45056 ($B000)
the values will hopefully tell us the memory bank address location of the eprom. Dumping them on an eprom programmer will help us understand what they are
SiRSKiNBAD
Member
Thanks for the help guys ! I don’t have anyway of dumping the roms at the moment.
You don’t need to write a wee program if it’s a hassle ? I was just curious if it was a certain command or code line I would run.
I’m completely new to basic so I’ll deffo have a look at some of the reading material!
You don’t need to write a wee program if it’s a hassle ? I was just curious if it was a certain command or code line I would run.
I’m completely new to basic so I’ll deffo have a look at some of the reading material!
daver2
10k Member
Try the following:
S is the start address of the memory to dump.
I is the byte offset of the memory to dump.
FOR I is the start of a loop
S+I accesses a specific byte of memory to examine
PEEK is a function that returns the byte value at the specified address S+I
NEXT I is the end of the FOR loop
END is obvious...
Change line "10 S = nnn" to match Andy's differing ROM start addresses.
Report back the values that are printed out.
Dave
Code:
10 S = 36864
20 FOR I = 0 TO 8
30 PRINT S+I," = ", PEEK( S+I )
40 NEXT I
50 ENDS is the start address of the memory to dump.
I is the byte offset of the memory to dump.
FOR I is the start of a loop
S+I accesses a specific byte of memory to examine
PEEK is a function that returns the byte value at the specified address S+I
NEXT I is the end of the FOR loop
END is obvious...
Change line "10 S = nnn" to match Andy's differing ROM start addresses.
Report back the values that are printed out.
Dave
SiRSKiNBAD
Member
Thanks for the code 
I’ll give it a try and let you know how I get on !
The pet is currently on my bench at work so it won’t be until Monday I can try !
I’ll give it a try and let you know how I get on !The pet is currently on my bench at work so it won’t be until Monday I can try !
SiRSKiNBAD
Member
daver2
10k Member
Ah ha!
So, the initial start-up message of "*** COMMODORE BASIC ***" tells me that the BASIC you have is the 'original' ROM code (that live from address $C000 to address $FFFF). Later versions of the ROM code have "### COMMODORE BASIC ###" and "*** COMMODORE BASIC 4.0 ***".
It would appear as though the little BASIC program has identified some ROM code at 45056 ($B000) - your third picture.
Try the command "SYS 45056" and see if your PET crashes or gives you some new commands for the disk...
Dave
So, the initial start-up message of "*** COMMODORE BASIC ***" tells me that the BASIC you have is the 'original' ROM code (that live from address $C000 to address $FFFF). Later versions of the ROM code have "### COMMODORE BASIC ###" and "*** COMMODORE BASIC 4.0 ***".
It would appear as though the little BASIC program has identified some ROM code at 45056 ($B000) - your third picture.
Try the command "SYS 45056" and see if your PET crashes or gives you some new commands for the disk...
Dave
SiRSKiNBAD
Member
Yeh, I found that sys45056 command in the manual for the drives and it looks give you access to the drives.
I tried commands like $dir,1 and $dir,2 and that looks like if I had a disk in drive 1 or 2 it would show me a file list. Other commands like $format, $load and $save look to work aswell. The manual also gives you various others but I don't have any media to try much else.
I tried commands like $dir,1 and $dir,2 and that looks like if I had a disk in drive 1 or 2 it would show me a file list. Other commands like $format, $load and $save look to work aswell. The manual also gives you various others but I don't have any media to try much else.
SiRSKiNBAD
Member
is a pet 2001-8 stuck at basic ? or can it run the later versions ?
daver2
10k Member
Ah, so you have a manual. I am glad our diagnosis turned up the same results!
You can upgrade (easily) to the 'fixed' version of the BASIC you have. However, all this gets you is a working IEEE488 port (generally used for disk access). As you already have a disk, this would (perhaps) be pointless...
If you try to upgrade to BASIC 4, this requires an extra ROM (or 2) occupying $Bxxx, thus overlaying your disk ROM. So this would shoot you in the foot!
Are you also asking about languages other than BASIC?
Dave
You can upgrade (easily) to the 'fixed' version of the BASIC you have. However, all this gets you is a working IEEE488 port (generally used for disk access). As you already have a disk, this would (perhaps) be pointless...
If you try to upgrade to BASIC 4, this requires an extra ROM (or 2) occupying $Bxxx, thus overlaying your disk ROM. So this would shoot you in the foot!
Are you also asking about languages other than BASIC?
Dave
Great news it is working …. Your PET is stuck at BASIC 1 unless you obtain a ROM/RAM plug in board (into the 6502 CPU socket). Basic 2 can be then available as it doesn’t use $B000….. However, the Computhink drives will not work with anything other than basic 1 with that eprom set I suspect and also the add on memory board would be made redundant.
I would leave it as is
I would leave it as is
Last edited:
daver2
10k Member
Or get a set of BASIC 2 ROMS - from what I remember, there is only 1 or 2 ROMS that are different to BASIC 1.
At least if you want to use the IEEE488 for purposes other than disks - it should now work!
Dave
At least if you want to use the IEEE488 for purposes other than disks - it should now work!
Dave
Hi Dave, from the photos I think the motherboard has 6450 ROM chips so I guess you can insert adapter boards to make it BASIC 2 upon reflection. Not sure the add on ROMS will work though as the address calls will be different …. Just a thought
daver2
10k Member
I don't think they are Andy.
From what I remember the ROM checksums were broadly the same - apart from a couple of them. I think Commodore themselves didn't want the expense of a brand new set of ROMs making - so they economised on the smallest number of changes necessary from BAASIC 1 to BASIC 2. I think the IEEE488 'driver' is segregated into one of the ROMs mainly.
You 'may' be able to find the odd BASIC 2 ROM come up on eBay (if you wait long enough).
Dave
From what I remember the ROM checksums were broadly the same - apart from a couple of them. I think Commodore themselves didn't want the expense of a brand new set of ROMs making - so they economised on the smallest number of changes necessary from BAASIC 1 to BASIC 2. I think the IEEE488 'driver' is segregated into one of the ROMs mainly.
You 'may' be able to find the odd BASIC 2 ROM come up on eBay (if you wait long enough).
Dave
Hi mate
just counted the number of pins on the rom chip shown in the photo on page 1. I counted 28 pins which means these are 6540 rom chips i believe. Retro Innovations make adapters for 27xx EPROMs…
andy
SiRSKiNBAD
Member
Thanks guys for help with this ! I really appreciate it !
Yeh, I don't have the original manual for the drives but managed to find a copy of it with some searching through some of the links in the above posts. Same for the expandamem board.
I'm not looking to upgrade or change basic, was more just curious if it was possible and by the sound of things it would be better to just leave it as.
I've actually just bought a wee c64 mini to play with basic on that.
.....and some classic games !
Honestly I'm now not really sure what to do with it ? I've had my fun stripping it down, cleaning it and messing about with the hardware to get it up and running. I do really like it though as a collection piece but its huge and I don't have the space for it. Would be a shame to just stick it back into storage.
I had a glance on ebay and prices seem all over the place for this model ?
If you dont mind me asking what would you think a value on it is ? Is ebay the best place or a collector forum like this ?
You can also tell me where to go ! I'd understand !
Thanks
Yeh, I don't have the original manual for the drives but managed to find a copy of it with some searching through some of the links in the above posts. Same for the expandamem board.
I'm not looking to upgrade or change basic, was more just curious if it was possible and by the sound of things it would be better to just leave it as.
I've actually just bought a wee c64 mini to play with basic on that.
.....and some classic games !Honestly I'm now not really sure what to do with it ? I've had my fun stripping it down, cleaning it and messing about with the hardware to get it up and running. I do really like it though as a collection piece but its huge and I don't have the space for it. Would be a shame to just stick it back into storage.
I had a glance on ebay and prices seem all over the place for this model ?
If you dont mind me asking what would you think a value on it is ? Is ebay the best place or a collector forum like this ?
You can also tell me where to go ! I'd understand !
Thanks
WimWalther
Experienced Member
Thank you. I kinda assumed this would be the case, but all of the cable images I could (briefly) search up had the Centronics conn. on both ends.
WimWalther
Experienced Member
As far as where to sell something like the PET - VCFED forum vs. eBay..
Ebay is likely where you'll realize the highest selling price, though not always if the machine is in particularly nice condition or has unique featurex. But of course, an eBay sale is a crapshoot, you really don't know who you're dealing with, and there are a number of ways to be abused or cheated by an unscrupulous buyer.
Selling here on VCFEC can provide the satisfaction of keeping it "in the family", and helping a fellow enthusiast obtain something they really want. You're also much less likely to be abused, if you're dealing with established members in good status. There are also no sellers fees here..
Ebay is likely where you'll realize the highest selling price, though not always if the machine is in particularly nice condition or has unique featurex. But of course, an eBay sale is a crapshoot, you really don't know who you're dealing with, and there are a number of ways to be abused or cheated by an unscrupulous buyer.
Selling here on VCFEC can provide the satisfaction of keeping it "in the family", and helping a fellow enthusiast obtain something they really want. You're also much less likely to be abused, if you're dealing with established members in good status. There are also no sellers fees here..