How to hack cartridges

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6502dude
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Postby 6502dude » Wed May 02, 2007 9:33 am

nbla000 wrote:I think it's a little bit harder to find this 2364->2764 adapter though seems to be easy to do but in any case what i think is:
Since a lot of cbm carts use an 8k rom and these roms are all of 24 pin may be that this roms are 2364 labelled by commodore with own part number, may be ? there is a way to check ?

2364->2764 adapter layout:
Image


The sure way to determine if ROM is a 2364 is to trace the circuit paths to the edge card connector. I figure the probability is high that it is a 2364.

There was post a while in this forum on these sort of adapters:

http://sleepingelephant.com/ipw-web/bul ... ht=adapter

Send me a PM with your contact details and I will mail you one. You will need to reveal your identity however :lol:

It is just a bare board, so you will need to source header pins and socket locally.
Image Mega-Cart: the ultimate cartridge for your Commodore Vic-20

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6502dude
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Postby 6502dude » Fri May 04, 2007 9:55 pm

I could not easily locate images for my 4K cartridge hack.

So here is an 8K version hack to convert to use 2764 eproms.

(1) Start with an cartridge with an 8K ROM image in in. In this case, I picked one that I have duplicates of:

[img]http://www.bjlyons.com/cbm/vic20\8K_cart_hack\8K_out.jpg[/img]

(2) Remove existing ROM chip

(3) Install 28 pin socket, bending pins 1,2,27 and 28 up and allowing other 24 pins to go thru 24 pin holes. Solder socket pins to underside of board.

[img]http://www.bjlyons.com/cbm/vic20\8K_cart_hack\8Khack_socket.jpg[/img]

(4) Wire pin 28 of socket to VCC and pin 2 to A12 with 30AWG wire

Note: the following pin references are to new 28 pin socket, not the old ROM pin numbers.

(5) Break existing trace from A12 to pin 23 of eprom socket

(6) Break existing trace from A11 to pin 20 of eprom socket

(7) Install jumper from pin 20 of eprom socket to pin 22 of eprom socket with 30AWG wire

(8 ) Install jumper from A11 to pin 23 of eprom socket with 30AWG wire

[img]http://www.bjlyons.com/cbm/vic20\8K_cart_hack\8Khack_under.jpg[/img]

(9) Burn game/utility rom image to 2764 & install in socket

[img]http://www.bjlyons.com/cbm/vic20\8K_cart_hack\8Khack_2764.jpg[/img]

(10) Install in Vic-20 & play game.

You now have a cartridge which you can change eproms on to play your favourtive games or test custom /BLK5 applications.
Image Mega-Cart: the ultimate cartridge for your Commodore Vic-20

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nbla000
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Postby nbla000 » Mon May 07, 2007 5:09 am

WOW :shock: i'm not so expert with my welder but these modification seems easy to do, i may try to destroy 2/3 cartridges before to contact a local hardware repairer.

Thank's a lot, now it's time to buy a Willem EPROM Programmer, seems it's easy to found on ebay, it's cheap, can burn 2732,2764,27128 etc and software works with Windows, other cheap alternatives ?

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Postby ral-clan » Mon May 07, 2007 8:20 am


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nbla000
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Postby nbla000 » Tue May 08, 2007 1:36 am

Very interesting, i need to investigate.
Thanks.

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6502dude
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Postby 6502dude » Tue May 08, 2007 6:31 am

ral-clan wrote:Would this article be helpful?

http://cbm.csbruce.com/~csbruce/cbm/tra ... /p064.html


Interesting article.

Use of 2564 8K eprom is mentioned within text, however this is a 28 prin eprom and not workable without a further circuit board hack.

Also, since expansion RAM is enabled, screen memory is relocated by Vic-20 kernel. This poses a problem for use of this cart for games.

Many cart based games rely on video/screen memory not be moved.

This hack may be a good solution for Vic-Mon, Hesmon and some other utility based cartridges that can use expanded memory.
Image Mega-Cart: the ultimate cartridge for your Commodore Vic-20

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nbla000
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Postby nbla000 » Tue May 08, 2007 9:38 am

6502dude wrote:This hack may be a good solution for Vic-Mon, Hesmon and some other utility based cartridges that can use expanded memory.

Yes i agree, it's a good solution but only if you burn eproms (2*4k) with tools that has not problems with additional ram, tipically not games.

Just a consideration, looking 6502dude work and my atari and cbm cartridges , atari and cbm carts have a different scheme but pins go at the same cart point, so i may assume that cbm cartridge use 2364 PROMS, it may be definitively assert?

Just another things, the atari cartridges that use 2*2364 PROM may change the memory address to 1/2/3/5 by cut or sold some circle, for example Donkey Kong and Centipede are designed for bank 1/5 but you may use 2*2764-->2364 adapter and burn 2*8k 2764 roms for any bank, typically 3/5.

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Mike
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Postby Mike » Tue May 08, 2007 10:37 am

6502dude wrote:Also, since expansion RAM is enabled, screen memory is relocated by Vic-20 kernel. This poses a problem for use of this cart for games.

A 3K RAM expansion does not move the screen memory. The additional memory appears at $0400-$0FFF, so BASIC still gets a continuous chunk from 1024 to 7679, with the screen starting at 7680, just as on an unexpanded VIC.

Michael

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Postby KilrPilr » Tue Jun 19, 2007 3:29 pm

I have tried to make 2 of these cartridges and neither of them work. Electronics are a PITA! I give up

eslapion
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Postby eslapion » Tue Jun 19, 2007 3:45 pm

KilrPilr wrote:I have tried to make 2 of these cartridges and neither of them work. Electronics are a PITA! I give up


How many do you want? Minimum order is 10 units @ 12$ each !!

:wink:

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Postby KilrPilr » Tue Jun 19, 2007 6:09 pm

thanks eslapion but its not that big of deal to have one.

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Postby eslapion » Tue Jun 19, 2007 6:41 pm

KilrPilr wrote:thanks eslapion but its not that big of deal to have one.


New PCBs...

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6502dude
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Postby 6502dude » Mon Jul 23, 2007 6:32 pm

I have made a few of the 8K hack cartridges for forum members and realized that my forum post "how-to" ommited tying /PGM line high. :oops:

Recently I got PM asking about a 16K cart.

Commodore was pretty cheap and did not extend /BLK1 /BLK2 lines out to edgecard connector for most of their carts. :cry:

I sorted through my collection of carts and found a few which do have /BLK1, BLK2, BLK3, & /BLK5 on edgecard.

While not many have traces on the circuit board, the edgecard connector contact is only inserted about 50% of the way into the edgecard socket.

If one is careful with solder, the top part of the tab on the edgecard can be used to connect to. :D

So with this in mind, and building on the 8K hack with use of 28 pin socket, I moved forward with a 16K hack cartridge.

I use a 74LS08 for decode logic:

Image

I used hot melt glue to afix the 74LS08 to the board and point to point wiring. It's not pretty, but it's cheap and it works!

27c256 eproms were used because I have a few of them and they are cheaper than buying 27C128 (16K eproms). Line A14 is tied to gnd.

Image

This hack supports any $2000, $4000, & $6000 image part in lower 8K space of 27256 eprom and $A000 piece is stored in 2nd 8k block. This has been tested with multiple images and works fine.

Next hack is 32K ram expansion with 74LS148 chip (using game cart board as host).
Image Mega-Cart: the ultimate cartridge for your Commodore Vic-20

eslapion
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Postby eslapion » Wed Jul 25, 2007 4:21 pm

If you do the above hack but with a 62256 RAM chip instead of the 27C256 and you put an appropriate connection or switch on the R/!W line to !WE pin in the RAM chip then what you get is very close to... the ultimate expander.

A slight difference concerning A14, however, I connected my LS08 in the following manner:

/BLK1 AND /BLK3 to A13
/BLK1 AND /BLK2 to A14
A14 AND (/BLK3 AND /BLK5) to /CE + /OE ->edit: line corrected

The resulting truth table is:

Input: ----------------- Output:
/B1 | /B2 | /B3 | /B5 | A14 | A13 | /CE + /OE
1 --- 1 ---- 1 ---- 1 ---- 1 ---- 1 ---- 1
0 --- 1 ---- 1 ---- 1 ---- 0 ---- 0 ---- 0
1 --- 0 ---- 1 ---- 1 ---- 0 ---- 1 ---- 0
1 --- 1 ---- 0 ---- 1 ---- 1 ---- 0 ---- 0
1 --- 1 ---- 1 ---- 0 ---- 1 ---- 1 ---- 0

There is your 32k RAM expansion but with a simpler LS08 instead of the LS148.

A simple SPDT switch that toggles the !WE pin of the SRAM chip between VR/W (cart port pin 17) and +5V via a 4.7k resistor can be used to switch your RAM expansion between Read-write and read-only mode for full compatibility with all cart images.

Also since you specify that you have a good number of 27c256, then by connecting your LS08 as I just mentioned, you could hack a commodore cart to become a host to a 32k game... if anybody ever felt like creating one... :wink:

The resulting address translation makes the following ROM address ranges visible to the VIC at these BLK areas:
$0000-$1FFF in the ROM for BLK1
$2000-$3FFF in the ROM for BLK2
$4000-$5FFF in the ROM for BLK3
$6000-$7FFF in the ROM for BLK5

These addresses, of course, are not VIC address ranges but addresses to use when programming your ROM chip.
Last edited by eslapion on Wed Jul 25, 2007 8:43 pm, edited 1 time in total.

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6502dude
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Postby 6502dude » Wed Jul 25, 2007 7:43 pm

eslapion wrote:A slight difference concerning A14, however, I connected my LS08 in the following manner:

/BLK1 AND /BLK3 to A13
/BLK1 AND /BLK2 to A14
A13 AND (/BLK3 AND /BLK5) to /CE + /OE


Great idea!

I have loads (a few hundred) 74LS08 chips, but only a few 74LS148 chips.

Is there a typo in last line?

Should it read:
A13 AND (/BLK2 AND /BLK5) to /CE + /OE

A simple SPDT switch that toggles the !WE pin of the SRAM chip between VR/W (cart port pin 17) and +5V via a 4.7k resistor can be used to switch your RAM expansion between Read-write and read-only mode for full compatibility with all cart images.

When I get around to building this, I will likley omit the socket & solder 62256 to board.
Since there is little need to pop the ram chip out, this will allow me to put case back on on top (to hide ugly upside down chip & wiring).
Image Mega-Cart: the ultimate cartridge for your Commodore Vic-20


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