40/80 column cartridge

vic user · Post by **vic user** » Mon Mar 20, 2006 10:05 am

in one of my pm'ing sessions with ral-clan, the memory locations for the characters on the 80 column screen was brought up, and i thought it would be good to share it with others who use the card:

47104 to 49023.

chris

ral-clan · Post by **ral-clan** » Thu Mar 30, 2006 9:07 am

The Data-20 40/80 column board is shown in a plastic case in the magazine advertisements of the time. However, I think that those on this message board who own one have just the bare circuit board. My theories about why there are so many bare Data-20 boards is that:

a) they were factory left-overs that were liquidated when the company went bust, or;

b) when they started using socketed EPROMs and socketed RAM chips (rather than soldered onto the board), the hieght was too great for the case design.

Anyway, I own one of these (bare) boards. Being bare, the chips are susceptable to a static zap from my finger or the underside of the board could touch something metal while it is powered - and that would mean zzzZAP

.

Since it's hard to replace these board, and I just love using it (thanks for getting me into it vic-20 user

), I decided to put it into a case.

I found out the NES cartridge cases are just about the right size:

but you still have to remove a lot of plastic with a dremel tool and saw off the narrow end of the case. After that the Data-20 board sits in absolutely perfectly, like it was made to fit.

Because of all those socketed chips, it's still a tight fit hieght wise, though. Some of the chips touch the top of the plastic case. Because I was paranoid about heat build-up, I drilled some vent holes over those chips (mostly the EPROM and video chip). I'm not sure if these chips even need it, but I'm not taking any chances.

Unfortunately, the simplest and most secure way to close everything was with some clear packing tape. Not very pretty (rather ugly actually), but it works.

I've installed the missing 8K of RAM on this board (thanks 6502dude) and also soldered on the missing switch which moves this RAM to either Block 1 or Block 5. The squarish hole in the case near the edge connector allows access to the (white) switch.

So there you have it. It's pretty brutish looking....looks like something from the Road Warrior movie. Personally I'd prefer something more elegant....but it's an improvement on a bare circuit board, and does the job of protecting the guts of this device.

Does anyone forsee any problems with this design?

As for using the NES cartridge casing: I'm not sure if I'd do it again. It was a perfect fit width-length wise, but I'd like something with a little more hieght. However, the NES carts are about the same thickness as a real VIC cartridge, so with this design I can at least be sure it will fit in a multislot expander between other cartridges, or in the VIC's rear expansion port.

Also, you have to dremel and cut almost every bit of extruding plastic inside the NES cartridge case....it's actually quite time consuming.

If you have a DATA-20 board like the above without socketed chips, the NES cartridge case would really be ideal.

Here is a picture of the whole setup working in dual monitor mode. I'm programming on the 40/80 column board at the right and poking (a coloured ball) to the 1702 monitor on the left.

You can see why I need to build that special multi-slot expander to go under the (official Commodore) monitor stand.

http://sleepingelephant.com/ipw-web/bul ... php?t=1106

Comments?

carlsson · Post by **carlsson** » Thu Mar 30, 2006 12:55 pm

It looks cool! Did you use two bottom sides of a NES cartridge? The upper side doesn't really look like it did before you went ahead with a Dremel.

ral-clan · Post by **ral-clan** » Thu Mar 30, 2006 1:18 pm

carlsson wrote:It looks cool! Did you use two bottom sides of a NES cartridge? The upper side doesn't really look like it did before you went ahead with a Dremel.

Good eye - actually I used the 'normal' halves of the NES cartridge, but flipped upside down. I had to made the bottom of the NES cartridge the top of the Data-20 case. This was because the bevel that is present at the edges of a NES cartridges 'bottom' prevented the Data-20 circuit board from sitting properly. They caused the circuit board of the DATA-20 board sit too high, and the cartridge case wouldn't close.

The 'top' of the NES cartridge doesn't have bevels, so it became the 'bottom' of the Data-20 case and the circuit board sat in there nicely.

Once I found this out I had to cut a new hole in the NES case for the monitor cable jack on the Data-20. So the black electrical tape is covering the old hole I made before I found out it wouldn't fit (messy, but in the end it worked).

vic user · Post by **vic user** » Thu Mar 30, 2006 2:40 pm

although i prefer your cart. case, if you want a real 40 column cart. case. i can give you one of mine as i never use them, and never intend on using it.

i am perhaps decadent in having two of these carts.

ral-clan · Post by **ral-clan** » Thu Mar 30, 2006 2:59 pm

vic user wrote:although i prefer your cart. case, if you want a real 40 column cart. case. i can give you one of mine as i never use them, and never intend on using it.

i am perhaps decadent in having two of these carts.

Oh! I wish I had known this before I started this project. I'll take you up on your offer, I'd like to have the 'proper' case, even if just as a spare.

vic user · Post by **vic user** » Thu Mar 30, 2006 3:06 pm

i will keep the case beside the dr. who videos ' )

ral-clan · Post by **ral-clan** » Thu Mar 30, 2006 3:15 pm

vic user wrote:although i prefer your cart. case, if you want a real 40 column cart. case. i can give you one of mine as i never use them, and never intend on using it.

i am perhaps decadent in having two of these carts.

Now that I know you had two cases for your Data20 board which you took off, that makes me think there is a third theory for why so many of these boards have no cases: people took them off so they could fit in between other cartridges on a multi-cart expander!

Schema · Post by **Schema** » Thu Mar 30, 2006 3:17 pm

My Data20 40/80 cart has the plastic case. It works OK in a cartridge expander as long as I put it in the front slot (closest to the VIC.)

Mikam73 · Post by **Mikam73** » Thu Mar 30, 2006 4:42 pm

I am not sure if I ask this already.. but does this work only with NTSC Vic20 or with PAL Vic20 too?

Is output NTSC signal?

ral-clan · Post by **ral-clan** » Thu Mar 30, 2006 7:50 pm

Mikam73 wrote:I am not sure if I ask this already.. but does this work only with NTSC Vic20 or with PAL Vic20 too?

Is output NTSC signal?

I am pretty sure it's an NTSC signal.

6502dude · Post by **6502dude** » Thu Mar 30, 2006 8:33 pm

With a different crystal frequency and altered values for 6845 register set up parameters, the native board should support PAL rather than NTSC

ral-clan · Post by **ral-clan** » Fri Mar 31, 2006 8:59 pm

carlsson wrote: When it comes to dumping, something like this should do the trick:

10 OPEN1,8,15:OPEN2,8,2,"DATA20DUMP,P,W"
15 PRINT#2,CHR$(0);CHR$(160);:REM Add load address
20 FOR I=40960 TO 49151:PRINT #2,CHR$(PEEK(I));:NEXT
25 CLOSE2:CLOSE1

Carlsson,

Hi, I tried using this program last night to dump the contents of my Data-20 EPROM. I'm afraid you'll have to explain to me how to use it as if I were a complete novice (which in the case of ROM dumping I am). I don't really understand (from the listing) what is going on.

When I run it as is I get an error in line 30, so I figure I must have to enter some sort of memory address....but I don't know where to enter it and what value?

Do I need a RAM expander plugged in to use this (i.e. RAM in a certain block)?

Sorry, I am a comlete idiot in this case....could you explain to me what to do in step by step terms?

saundby · Post by **saundby** » Sat Apr 01, 2006 3:23 am

ral-clan wrote:
carlsson wrote: When it comes to dumping, something like this should do the trick:

10 OPEN1,8,15:OPEN2,8,2,"DATA20DUMP,P,W"
15 PRINT#2,CHR$(0);CHR$(160);:REM Add load address
20 FOR I=40960 TO 49151:PRINT #2,CHR$(PEEK(I));:NEXT
25 CLOSE2:CLOSE1
Carlsson,

Hi, I tried using this program last night to dump the contents of my Data-20 EPROM. I'm afraid you'll have to explain to me how to use it as if I were a complete novice (which in the case of ROM dumping I am). I don't really understand (from the listing) what is going on.

When I run it as is I get an error in line 30, so I figure I must have to enter some sort of memory address....but I don't know where to enter it and what value?

Do I need a RAM expander plugged in to use this (i.e. RAM in a certain block)?

Sorry, I am a comlete idiot in this case....could you explain to me what to do in step by step terms?

His program is used to write a data file to a disk drive containing the contents of the ROM in the Data20. The ROM addresses are provided in the FOR statement. The REM is stating that he's set the address earlier in the line at which the "program" will be loaded back. In this case it appears to be $A000. So you could then load it back into RAM at $A000 for perusal.

Here's an article that will help explain some things:
http://www.atarimagazines.com/compute/i ... modore.php

saundby · Post by **saundby** » Sat Apr 01, 2006 3:26 am

Slick trick with the cart case, btw. And yes, I see why you need a low-profile motherboard. You've got about fourteen more inches in width for your space than I've got, which is why I don't have my green screen going again yet.

But yes, that C= monitor stand is =low=. Perhaps you could give yourself another half inch by putting some thick rubber feet on the bottom of it? I've used that trick more than once myself.