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CBM 8032 software mod 40 column screen too small

terryfi

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Jul 5, 2022
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Hello everyone,

I recently fixed a broken 8032 PET by replacing its CRTC with Rockwell R6545-1P.
This PET is 80 columns by default so I decided to use cbm4032 any hz.prg to soft mod it to 40 columns.

The 40 columns work but screen is too small, is this expected?
I understand if pixel size doesn't change 40 column would take half of width but can't we get the pixel size being adjusted proportionally so we have a full-screen 40 column mode?
Does doing the hardware mod, changing jumper connections on motherboard, fix this issue?
 

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daver2

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>>> The 40 columns work but screen is too small, is this expected?

IMHO - yes.

>>> Does doing the hardware mod, changing jumper connections on motherboard, fix this issue?

Yes.

However, you can have 40 or 80 columns - not both. There is a little third-party 'switch board' to permit changing from 40 to 80 columns 'on the fly'. But you may also require a modified EDIT ROM.

Dave
 

Eudimorphodon

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Long and short of it, you can’t fix it in software. The program you’re using is changing what it can, IE, how many characters it displays per scanline. The CRTC has no control of the actual pixel generation hardware and therefore cannot change the dot clock. (Machines with CRTCs that do support different resolutions have to implement the soft switches for this on their own.)
 

terryfi

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Jul 5, 2022
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Last edited:

daver2

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It has to be a universal or a universal 2 to have the 40/80 jumper block - but I might be wrong on this count...

Dave
 

MikeS

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It has to be a universal or a universal 2 to have the 40/80 jumper block - but I might be wrong on this count...

Dave
No, you're quite right!

There are three board versions:
8032089 - this is the one for which the switcher was designed.
8032080 - the switcher can be made to work with this one with a minor adjustment.
8032030 - incompatible with the switcher since there is no jumper block.

See the enhanced switcher here for more info:

And the board layout for the 8032089:

m
 

eebuckeye

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Feb 9, 2008
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United States
I'm hoping someone notices this as I would really like to use my 8032 at 40 columns for the majority of PET software. The picture attached seems to me to show 8032090 but that is not an option of a board version. Am I miss reading it?
 

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daver2

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That is the Universal 2 board and should correspond to this link http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/univ2/8032090-7.gif

You should see the 40/80 column link block on this board, so you should be good to go.

Be aware that the PCB board, schematics, parts list, assembly etc. all have their own drawing numbers. This is where some confusion can creep in when referring to (say) the schematic drawing numbers. This will be different to the actual number stamped onto the physical PCB.

If you use the jumper block, you 'hard code' the PET to either 40 or 80 columns.

If you fit the switcher, you can (as the name states) switch between 40 and 80 columns.

Dave
 

AndyG

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Oct 11, 2016
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394
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UK
Thank you! Does anyone make the switcher to buy currently?
The designs are posted on Steve Grays GitHub page … the pcbs are easy to makeup. There was a guy selling the bare boards on eBay USA (155485891385). I have a couple of bare boards but am in the UK (ordered boards using Steve’s Gerbers from JLCPCB)


 

sjgray

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Feb 3, 2009
Messages
471
Location
Markham, Ontario, Canada
Thanks Mike and Andy! There is also an assembly guide on my page. Sadly, I have not gotten a chance to try my board on the first universal board, so if anyone wants to give it a try let me know how it works out, or contact me and we can sort it out together.

Steve
 
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