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View Full Version : PET "Fat 40" 4032 RAM expansion, 80-col & IDE mods, etc.



gsteemso
October 14th, 2009, 07:37 AM
Hi all,

First, RAM expansion:

I have looked at various sites online; one even sells NOS 64K RAM upgrades for the 8032, albeit at a high enough price I'd rather try to build my own. Alas, the only expansion header pinouts I was able to find were for the 8296, with a confusing "differences table" to the older 8032 board. According to a site that discussed the four types of PET system board, mine is what that site called a "type 3b" — a modified 8032 board that could support either 40 or 80 columns, 40 in my case.

I have heard that it is possible to add some chips and change some jumpers around to make the 4032 into an 8032, but while I found some schematics describing which jumpers to change, I haven't found anything about what chips to add, or where.

I've also heard rumours of an internal IDE mod where someone put a hard drive in his PET. That'd be seriously cool if it's true. Anyone know more?

If I get all of these changes made it'd be a fun project to try and port GEOS to the PET, using the ersatz bitmap mode provided by the block characters. Woohoo, a 160x50-pixel screen! :¬)

sjgray
October 14th, 2009, 11:54 AM
Hi,

Zimmers has schematics for most PET boards. Look on your board and find the matching schematics to find which chips you need to add and which jumpers to change.

Not a lot of software will use that extra ram even if you do install it. But if you plan to write your own software that won't matter.

Commodore did produce a "High Speed Graphics" board for the PET machines. This used a Thompson GPU and came with it's own 32K ram. You could draw lines, circles and plot multi-size text with the routines in ROM on the board.
There were also bitmap boards from third-parties such as MTU.

The IDE interface is very simple. You only need a few chips. It's the firmware that would be difficult to make it accessable in the standard commodore way. There are a couple IDE interfaces available for the C64 but I'm not aware of any for the PET. There were S-100 adapters for the PET and disk interfaces in the old days. There are IEEE hard drives like the commodore 9060 and 9090, and some third-party drives. There is one on ebay uk right now.

Check out the "UltraPET Project" on my web site:
http://www.6502.org/users/sjgray/projects/ultrapet/index.html

It encompasses some of the ideas you mention.

Steve

hexsane
October 14th, 2009, 05:10 PM
Where can I get my hands on one of the MMU boards? Or the schematic?

-Matt

sjgray
October 15th, 2009, 05:01 AM
Where can I get my hands on one of the MMU boards? Or the schematic?

-Matt

The MMU board was made by TPUG. Unfortunately, just recently, they sold the last three remaining boards. I inquired about the boards two years ago but nothing happened until recently and I still DIDN'T get a board.... I did get a scan of the board and I hope to make my own but I haven't had time to reverse-engineer the schematics yet.

You could contact TPUG but I'm not sure how much luck you will have. I know there were other people trying to reverse engineer the board but I don't know if or when that might be available. I will make some inquiries...

Steve

sjgray
October 15th, 2009, 06:07 AM
If I get all of these changes made it'd be a fun project to try and port GEOS to the PET, using the ersatz bitmap mode provided by the block characters. Woohoo, a 160x50-pixel screen! :¬)

You could also replace the character set ROM with a set containing all combinations of 2x4 blocks so you could make a 160x100 pixel screen. I suppose with expansion ram you could build a virtual screen of any size and have the real screen a window into it that could be scrolled around as needed...

Steve

sjgray
October 15th, 2009, 12:41 PM
Here is some info on a PET IDE interface, which seem to be a work in progress (perhaps) at the moment:

http://petcbmide.blogspot.com/

MikeS
October 15th, 2009, 01:51 PM
Hi all,

First, RAM expansion:

I have looked at various sites online; one even sells NOS 64K RAM upgrades for the 8032, albeit at a high enough price I'd rather try to build my own. Alas, the only expansion header pinouts I was able to find were for the 8296, with a confusing "differences table" to the older 8032 board. According to a site that discussed the four types of PET system board, mine is what that site called a "type 3b" — a modified 8032 board that could support either 40 or 80 columns, 40 in my case.

I have heard that it is possible to add some chips and change some jumpers around to make the 4032 into an 8032, but while I found some schematics describing which jumpers to change, I haven't found anything about what chips to add, or where.

I've also heard rumours of an internal IDE mod where someone put a hard drive in his PET. That'd be seriously cool if it's true. Anyone know more?

If I get all of these changes made it'd be a fun project to try and port GEOS to the PET, using the ersatz bitmap mode provided by the block characters. Woohoo, a 160x50-pixel screen! :¬)
I assume that by now you've found the pinout for the 40/8032 expansion port and the 5 chips you need to add to the 4032 (UC6&7-2114,UB6&7-LS244,UB8-LS373) and the different editor ROM.
I'm curious: where'd you find the info on the jumpers?

gsteemso
October 16th, 2009, 07:53 PM
I assume that by now you've found the pinout for the 40/8032 expansion port and the 5 chips you need to add to the 4032 (UC6&7-2114,UB6&7-LS244,UB8-LS373) and the different editor ROM.
I'm curious: where'd you find the info on the jumpers?

Well, the board revision #3b schematics, wherever it was I found them (it was one of the major sites) showed the alternate positions of ALL the jumper pads on the board, including the ones controlling RAM size (8, 16 or 32 KiB). The only information I have found on anything else is what I presented above, so no, I haven’t found the data I need except in a cross-my-fingers-and-make-educated-guesses kind of way. If you know it, please refer me.

Thanks,
G.

billdeg
October 17th, 2009, 04:50 AM
FYI

"The CBM 64K memory expansion board kit that converts the 8032 into an 8096 will also operate on the "FAT 40" 4032. The operation is the same as on the 8096."

Summarized from the Commodore Midwest Regional Staff Newsletter April 15, 1982



Bill

sjgray
October 17th, 2009, 05:01 AM
First, I assume you looked here to find you have a "3b" board:
http://www.6502.org/users/andre/petindex/boards.html

It notes that there were two revisions of this board, so perhaps you could tell us the actual assembly# of the board you have so we're all on the same page.

Second, I assume you've looked at the schematics at zimmers. Which one matches your board?:
http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/univ/index.html
or
http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/univ2/index.html


The memory expansion connector can be found on page 1 of the schematics.

Third, in order for 80 columns to work properly you will need a new editor ROM, which can be downloaded from here:
http://www.zimmers.net/anonftp/pub/cbm/firmware/computers/pet/index.html
Which one you need depends on your keyboard (N=normal, B=business) and which frequency you have (50 or 60). Most 4032's had "N" keyboards, and since you are in the US I will assume you have a 60 Hz machine.

Steve

gsteemso
October 17th, 2009, 02:07 PM
First, I assume you looked here to find you have a "3b" board:
http://www.6502.org/users/andre/petindex/boards.html

Yeah, that was it! I knew it was somewhere major.


It notes that there were two revisions of this board, so perhaps you could tell us the actual assembly# of the board you have so we're all on the same page.

Hmm, good call. After considerable searching, I found the assembly number 8032080 on the identifier area of the board. This matches the diagram below:


Second, I assume you've looked at the schematics at zimmers. Which one matches your board?:
http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/univ/index.html
or
http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/univ2/index.html

Happily, the 8032080-07 picture matches my board exactly. Nice to have that nailed down.


The memory expansion connector can be found on page 1 of the schematics.

Wow, that's a bit bewildering. Informative though. Do you know where I can find stuff like timing information?


Third, in order for 80 columns to work properly you will need a new editor ROM, which can be downloaded from here:
http://www.zimmers.net/anonftp/pub/cbm/firmware/computers/pet/index.html
Which one you need depends on your keyboard (N=normal, B=business) and which frequency you have (50 or 60). Most 4032's had "N" keyboards, and since you are in the US I will assume you have a 60 Hz machine.

I do indeed. I figured I’d probably need a different ROM, but wasn’t going to worry too much about it until I sorted out the rest of the project.

Thanks again for your help,

G.

Keal
October 21st, 2009, 05:47 AM
You could also replace the character set ROM with a set containing all combinations of 2x4 blocks so you could make a 160x100 pixel screen. I suppose with expansion ram you could build a virtual screen of any size and have the real screen a window into it that could be scrolled around as needed...

Steve

Using REVERSE he could double that to 4x4 for even higher res.

sjgray
October 21st, 2009, 05:52 AM
Using REVERSE he could double that to 4x4 for even higher res.

Nope, 2x4=8... 2^8=256 combinations... so you would need the entire character set, including reverse to generate them.

Steve

hexsane
November 26th, 2009, 01:44 AM
Third, in order for 80 columns to work properly you will need a new editor ROM, which can be downloaded from here:
http://www.zimmers.net/anonftp/pub/cbm/firmware/computers/pet/index.html
Which one you need depends on your keyboard (N=normal, B=business) and which frequency you have (50 or 60). Most 4032's had "N" keyboards, and since you are in the US I will assume you have a 60 Hz machine.

Steve

There isn't an edit-4-80-n ROM that I can see. Does anyone know where this ROM may be? TPUG did a series of articles in TORPET circa 1981/1982 about doing the fat 40 to 8032 conversion:
http://www.tpug.ca/archive/torpet/Torpet_Issue_7_Oct_1981.pdf
http://www.tpug.ca/archive/torpet/Torpet_Issue_8_January_1982.pdf

I'm in the process of doing this conversion. Am hoping someone already has the ROM so I don't have to hack one together myself (There is already enough hardware modifications to do!).

-Matt

sjgray
November 26th, 2009, 06:16 AM
There isn't an edit-4-80-n ROM that I can see. Does anyone know where this ROM may be? TPUG did a series of articles in TORPET circa 1981/1982 about doing the fat 40 to 8032 conversion:
http://www.tpug.ca/archive/torpet/Torpet_Issue_7_Oct_1981.pdf
http://www.tpug.ca/archive/torpet/Torpet_Issue_8_January_1982.pdf

I'm in the process of doing this conversion. Am hoping someone already has the ROM so I don't have to hack one together myself (There is already enough hardware modifications to do!).

-Matt

Hmm, I didn't realize some were missing. I don't know if that's because it doesn't exist, or has just not been located. I don't think one would be too hard to make, given the info in those TPUG articles.

It would be great for someone to do the conversion and document it with photos so others can benefit. When I get some time I plan on doing a conversion of my 8296 board and I think I will have the same issue with no 40-column rom available for it. I hope to investigate whether I could make a hardware/software solution to allow the machine to switch between 40 and 80 columns on the fly via print chr$(something) or sys call.

Steve

carlsson
November 26th, 2009, 07:05 AM
Apart from any Fat 40 converted computers, would there ever have existed a 8000 series PET with the N keyboard? I think most of the ROM dumps origin from original production machines, and if this variant never was sold, likely nobody in recent time has a dump neither.

brain
November 26th, 2009, 05:47 PM
The MMU board was made by TPUG. Unfortunately, just recently, they sold the last three remaining boards. I inquired about the boards two years ago but nothing happened until recently and I still DIDN'T get a board.... I did get a scan of the board and I hope to make my own but I haven't had time to reverse-engineer the schematics yet.

You could contact TPUG but I'm not sure how much luck you will have. I know there were other people trying to reverse engineer the board but I don't know if or when that might be available. I will make some inquiries...

Steve

Are you talking about the board that allows OS/9 to run on the SuperPET?

Jim

hexsane
November 26th, 2009, 06:28 PM
Are you talking about the board that allows OS/9 to run on the SuperPET?

Jim

Yes.

-Matt

hexsane
November 27th, 2009, 02:46 AM
I have almost completed the conversion on a Universal Board 2 and am running in 80 columns. The keyboard table isn't correct for the N type keyboard yet I'll have to debug it later today after some sleep (almost 6 AM). Shifting appears to work properly. I think there are additional keys on the business keyboard that I'll have to hardwire to some momentary switches but I expected that. I didn't have enough lighting when I did the before pictures so I'll only be able to publish the end results. I'll make the new ROM available for download when I've figured out what I did wrong with the table mapping.

-Matt

hexsane
November 28th, 2009, 12:37 AM
PET 4032 to 8032 upgrade instructions:

http://linkdirectory.tv/articles/article-720.html

If you need the new ROM the link for it is near the bottom of the page.

-Matt

MikeS
November 30th, 2009, 10:05 PM
Very nice, Matt!

I did the same thing many years ago, but in the other direction, i.e. convert an 8032 to a 4032; much easier, and I didn't replace the ROM either, just used an external N type keyboard.

I did do one thing differently: after removing the 8032 jumpers I inserted header pins in all the jumper holes and used jumper blocks and wires. That made it easily reversible, and since I had a 2001 as well it was indeed returned to 8032 mode and stayed there, especially after I got a 4032. Also, when I did it I planned to add a few chips (or even a couple of multi-pole relays) which would connect to those headers to make it switch-selectable, but that never got off the drawing board.

Lots of fun.

sjgray
December 1st, 2009, 04:25 AM
Also, when I did it I planned to add a few chips (or even a couple of multi-pole relays) which would connect to those headers to make it switch-selectable, but that never got off the drawing board.

I would like to build a switchable circuit myself. It would be nice if it could be software switchable. Plus the Editor ROM would need to be modified to support both 40 and 80 column.

Steve

MikeS
December 1st, 2009, 04:46 AM
I would like to build a switchable circuit myself. It would be nice if it could be software switchable. Plus the Editor ROM would need to be modified to support both 40 and 80 column.

SteveI think the only thing that might be tricky is adjusting the screen size/location if it's different enough to be ugly. The ROM should be easy, esp. if you start with a Fat 40 (thanks to Matt); my 2001 has a ROM that can switch between BASIC 1 and BASIC 2/3, same idea. Presumably you could use a bit in one of the VIAs to do the switching. What would you pick for the actual switches/multiplexers?

sjgray
December 1st, 2009, 04:56 PM
I think the only thing that might be tricky is adjusting the screen size/location if it's different enough to be ugly. The ROM should be easy, esp. if you start with a Fat 40 (thanks to Matt); my 2001 has a ROM that can switch between BASIC 1 and BASIC 2/3, same idea. Presumably you could use a bit in one of the VIAs to do the switching. What would you pick for the actual switches/multiplexers?

I think rather than switching ROMs, I'd want to re-write the Editor ROM to support both 40 and 80 columns. Then I can add support to change modes with ?chr$(something) which would switch modes and adjust the CRTC registers to get the best video in both modes (perhaps chr 130 and 132 could switch as they are unassigned in both PET and C64/VIC).

Three 74LS157's should work for the address buss switching (10 lines) and clocking (2 lines). The CA1 line looks free to use as a select but it's also available on the user port so it might cause incompatibilities.

Steve

MikeS
December 1st, 2009, 05:53 PM
I think rather than switching ROMs, I'd want to re-write the Editor ROM to support both 40 and 80 columns. Then I can add support to change modes with ?chr$(something) which would switch modes and adjust the CRTC registers to get the best video in both modes (perhaps chr 130 and 132 could switch as they are unassigned in both PET and C64/VIC).

Three 74LS157's should work for the address buss switching (10 lines) and clocking (2 lines). The CA1 line looks free to use as a select but it's also available on the user port so it might cause incompatibilities.

SteveAh, well, you're more ambitious than I was; sounds like a worthy project indeed. Great idea to use a pair of screen codes instead of POKEs.

I didn't look at the details this time around but for some reason I had the idea that some of the switched lines were bidirectional; obviously not, so a '157 sounds like the answer all right.

By any chance could you use an I/O line that's used for the second cassette? Not much use for that any longer.

ayates
December 6th, 2010, 04:39 PM
I did the 40/80 column mod to my PET back when the Torpet article was first published. While I initially had a moveable header strip for the jumps (a piece of breadboard with every other joiner pulled out) I switched it over to fully electronic switching. See attached photos. I can dig out more detail if anyone needs it. The mod still works, I powered on the PET last night after it sitting dormant a good 20 years and I could flick back and forth between 40 and 80 columns.


Allan.

4908 4909

MikeS
December 6th, 2010, 05:17 PM
Nice job! Exactly what I had in mind; got as far as installing the headers and pins so I can switch by moving the jumpers, but then I picked up a 4032 and it didn't seem that important any more ;-)

sjgray
December 7th, 2010, 04:29 AM
Yes, nice work. I wonder why Commodore never thought of doing that? A dual 40/80 machine would have been a nice upgrade and would have kept compatibility with all the 40 column software already available.

If you have schematics that would be great!

Steve

sjgray
December 7th, 2010, 04:43 AM
This might be a good time to mention another project I have started...

If anyone is familiar with the CBM-II High Profile machines you will know that they have 8x14 pixel characters, which give them a nicer look. I designed a small adapter for the PETs character generator ROM that shifts the bits around a little (for 16 bytes per character). A couple wires to the CRTC chip and some re-programming should be all that is needed to have the same capability on the 4000/800 series PETs. I haven't built the adapter yet, but if anyone is interested I will post the info on my UltraPET web page (http://www.6502.org/users/sjgray/projects/ultrapet/index.html).

Steve

Steve