40/80 column cartridge

vic user · Post by **vic user** » Tue Apr 20, 2004 7:08 pm

I just got my 40/80 column cart. in the mail today.

I can't wait to play around with this thing, but the darn hockey playoffs are getting in the way, and I actually like soccer more, but what can you do when you are a Canadian during the playoffs

I did look over the manual, and also of course actually try the cart., and I now know how they get around the VIC chip.

They don't.

The cart. uses block 5, and you simply plug your video DIN plug to the cart., (it has a jack), and that is how they do the 40/80 column effect.

Thus I could still plug in from the normal video out and go to another TV or monitor and still get output.

I am starting to think that this will be an excellent way for me to also use the light pen and another video device, as a kind of glorified graphics tablet.

I still need to play around with this cartridge though, but it sure is strange seeing the vic 20 able to display 40 columns.

The resolution looks very similar to a Commodore 64.

80 columns is an instant headache for me, using a 1701 monitor.

It also has a builtl in terminal program, and some other features very similar to the prog. aid cart.

Chris

aneurysm · Post by **aneurysm** » Tue Apr 20, 2004 10:31 pm

i remember looking at that thing on eBay
i figured if I plan on buying a PET or CBM someday that I could just hold out for that though....
but I would like to hear more of what it does

Post by **Jeff-20** » Wed Apr 21, 2004 12:23 am

this is just a software trick right? I think I remember trying it with my x1541 cable a few years back after getting the rom from funnet or somewhere. It was interesting.

carlsson · Post by **carlsson** » Wed Apr 21, 2004 5:39 am

No, Chris' cartridge probably has its own video chip which produces a 40- or 80 column display, totally independent from the VIC-I chip and controlled either through the cartridge ROM space or some of the unused I/O blocks.

Basic has a few pointers in the low 1K which gives the address to the routine which prints things on screen, and the cartridge might rewire those pointers to itself, so all Basic output will end up on the display connected from the cartridge. Maybe it can be turned off with a SYS or POKE. If that is how it works, I assume regular POKEs to VIC-I, screen memory etc will end up on the "old" display as usual. Any Basic program or other which mixes PRINT and POKE should in that case look funny.

vic user · Post by **vic user** » Wed Apr 21, 2004 6:35 am

From what I have read so far, Anders seems right on the money.

I will jot down the the specs of the cart. when I get home, especially the memory locations for things.

I really want to use two video outputs, and then fiddle and see the differences on each screen.

At least I can now use one of my vic's that only displays in shades of grey, as the cart. deals with the display now, and I can give my other vic's a rest back in their boxes.

Chris

Post by **Jeff-20** » Wed Apr 21, 2004 11:13 am

The software I saw produced a font similar to the opening scene in Omega Race... an abreviated font.

I have never seen the one you have.

carlsson · Post by **carlsson** » Thu Apr 22, 2004 12:52 am

Yep, the software solution to make 40x24 characters which are 4x8 pixels each is well known and exists in a handful implementations; some commercial and some more homebrewn (free).

I like to be spot-on, especially about things I really don't know anything about but just make assumptions. Since this cart does 80 columns, it was quite obvious that it has to do something else than a software VIC-I solution (try to make some 2x8 pixel characters yourself and see if it is readable :-).

What I really would like to get my hands on is a 6563 chip (6562 for you who live in NTSC land). It was Commodore's 40 column drop-in replacement for VIC-I which never was mass produced as they developed another 40 column computer instead (guess which one). The idea was to sell a VIC-40 as well as the chip and a Kernel upgrade to let current VIC-20 owners upgrade to VIC-40. I've seen the official specs, and they look interesting. One or a few prototype chips exist, and someone demonstrated how it works inside a VIC-20, minus the upgraded Kernel.

vic user · Post by **vic user** » Thu Apr 22, 2004 6:06 am

I would like to know more about that chip you are talking about Anders, or better still, have a vic 20 with it!

Here is what I can kind of make out on the 40/80 column manual (it's extremely hard to read, as it is a photocopy of a photocopy etc...)

Data 20 Display Manager

Functions added:
40 columns by 24 lines
80 columns by 24 lines
8k memory
bulit in terminal emulation

Video Column selection:
software selectable

Video output:
1.75 (not sure about the last digit) RS-170 compatible standard composite video 75 ohm, black and white

Video output connection:
5 pin DIN, vic 20 pinouts

Modulator compatibility:
can use vic video modulator in 40 column mode

Character set:
full commodore character set

Video memory:
2k at hex 8800

firmware provided:
2k video driver at A000

Chris

carlsson · Post by **carlsson** » Thu Apr 22, 2004 7:26 am

VIC-40 story: http://www.floodgap.com/retrobits/ckb/secret/vic40.html
Datasheet: http://www.6502.org/datasheets/6562.jpg

Unfortunately, only the first page of the datasheet exists on the Internet, so it is hard to understand exactly what MOS meant by "three waveforms and three amplitude modulators" on the sound part of the chip.

Hmm.. the video memory ($8800) on your cartridge shadows the alternative character set (lower case) inside the VIC. Maybe it isn't a big loss, as the VIC-I will be able to read from the ROM anyway, but you can not copy the lower case font into RAM if I understand it correctly. I assume the supplied character set is more like the C64 one than the VIC one and probably is located somewhere in the range $A800-$BFFF (6K).

Is the 8K memory a regular expansion (at $2000) or do they include the "cost" of firmware, video matrix etc into that figure? The most interesting thing should be that with the video matrix at $8800, you could in theory have a 3+4+8+8+8 = 31K large Basic program into memory as long as you use the 40 column output.

carlsson · Post by **carlsson** » Thu Apr 22, 2004 7:37 am

Of course, the VIC-20 also has something similar to waveforms it seems:

http://mikrolahti.fi/~ae/download/vicdocs.zip

See the document "waveforms.txt". It was found by Viznut of PWP in June last year. The theory is by careful timing and feeding the right values to the oscillators, one can generate different pulse widths and thus make the sound sound different (normally more thin or metallic).

I haven't yet tried it myself, but some day I'll follow the instructions and see what I can do. Viznut himself has included the technology in his latest VIC demos. It maybe is a little too technical here, but once we understand how to do it, it could be great fun to get new sounds.

Maybe what MOS was planning with the 6562/63 was to make three out of the 16 possible values official pulse waves, but the three amplitude (volume) registers also sound interesting.

vic user · Post by **vic user** » Thu Apr 22, 2004 8:20 am

That waveform thing sounds (pardon the pun), like "aneurysm" would be interested in this

Chris

vic user · Post by **vic user** » Thu Apr 22, 2004 8:32 am

Here is some more stuff I can pick out from the manual:

in order to use 3k memory expansion (like from the super expander) you will have to tell the computer that there is an extra 3k.

to do, you poke 642,4: sys 59232

To use an additional 8k, set the 8k cart to block 2.

To use 16k, you have to move the display manager's 8k to block 3, my removing the case and moving the appropriate DIP switch.

Display manager memory map:

39920
CAT controller, control / data register

39932
mode register
bit 0: 1 (lower case characters)

bit 5: 1 (80 columns)

bit 5: 0 (40 columns)

40880-43007
driver software

47104-49151
video RAM

sys 40988 - 40 column mode
sys 40972 - 80 column mode
sys 40975 - return to vic 22 column screen
sys 40978 - restart 40 or 80 column mode without clearing screen contents

screen dump:
open 127,4
print #127,chr$(139)

chris

aneurysm · Post by **aneurysm** » Thu Apr 22, 2004 12:06 pm

vic user wrote:That waveform thing sounds (pardon the pun), like "aneurysm" would be interested in this

aww... we're getting to know each other

carlsson · Post by **carlsson** » Thu Apr 22, 2004 1:46 pm

Hmm.. a lot of interesting things there. I/O block 2 is normally unused and until now only (?) known to be used by the Rabbit tape fastloader, so these two units may not work together.

I/O Block 2 : $9800-$9BFF
$9BF0 (39920) : control registers
I/O Block 3 : $9C00-$9FFF
$9FB0 (40880) : driver software begins
RAM/ROM space : $A000-$BFFF
$A7FF (43007) : driver software ends
$B800 (47104) : video matrix begins
$BFFF (49151) : video matrix ends

The video matrix is enough to hold 80x24 characters, and no longer shadows the VIC character ROM.

I wonder if anything else of the $9800-$9FB0 registers is in use, and most importantly, what lurks in the undocumented 4K between $A800 and $B7FF. Maybe some colour memory, as you said it can display in a few different grey scales?

vic user · Post by **vic user** » Thu Apr 22, 2004 5:40 pm

I wonder if anything else of the $9800-$9FB0 registers is in use, and most importantly, what lurks in the undocumented 4K between $A800 and $B7FF. Maybe some colour memory, as you said it can display in a few different grey scales?

The cart. only displays in b&w. It is the specific vic 20 that I am using that only displays in shades of grey, as there is something wrong with it. That's why I am happy to be able to use this vic with the cart., as now you cannot tell there is anything wrong with the vic

I wish i could teleport the cart. over to you, so you could fiddle with it, and find out what you want to know, as you obviously have more know how than me.

chris