How to hack cartridges

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nbla000
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Postby nbla000 » Sat May 03, 2008 3:26 pm

eslapion wrote:However, replacing the standard flash memory chip with a nvsRAM chip would allow people to direcly "poke" data into the permanent memory withput the need for a special software.


Yes but is not the same if you use a Menu with 7 different music tunes, categories, favorites, custom items, special boot keys, all carts already put inside plus a lot of tape/disk games, a reset system to avoid to switch off/on the vic each time, memory expansions, etc etc etc...

And without software you cannot load in an hypothetical "MegaDrive" normal programs for unexpanded/3/8/16/24k vics, you may simply put datas on BLK5 and/or BLK1-2-3 but how to start them ?
POKEs may simply select which part of eprom/flash rom/nvsRAM you see in a certain BLK but this is not enough to start a non cart game....

So you need software and i need easy hardware :wink:
Mega-Cart: the cartridge you plug in once and for all.

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6502dude
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Postby 6502dude » Sat May 03, 2008 5:55 pm

Here is image of result of great idea to have switch select between BLK3 & BLK5.


Image

I'm still using blue wire, but I have recycled a bit of white wire as well. :lol:

There are no traces cut on PCBs. I have simply cut off old ROM chips with dremel tool. This saves a lot of time from desoldering old ROM chip. :D

300 mil chip leads have been bent to reach pins on PCB. This is not as pretty as a 600 mil chip, but time saving is enormous.

Now back to MegaCart :D
Last edited by 6502dude on Mon Mar 26, 2012 7:12 pm, edited 1 time in total.
Image Mega-Cart: the ultimate cartridge for your Commodore Vic-20

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nbla000
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Postby nbla000 » Sun May 04, 2008 6:37 am

6502dude wrote:Here is image of result of great idea to have switch select between BLK3 & BLK5.

My suggested BLK3 & BLK5 idea in your last hack sounds good :D

I'm just modifying Tetris Deluxe to store hi-scores using it, i will send you a copy when finished.

I'm glad to test one of these hacks too :roll:

Now back to MegaCart :D


I will modify Tetris Deluxe to store hi-scores on MegaCart too. 8)
Mega-Cart: the cartridge you plug in once and for all.

eslapion
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Postby eslapion » Sun May 04, 2008 7:20 am

6502dude wrote:Here is image of result of great idea to have switch select between BLK3 & BLK5.


If you make a cart like that that uses the a 32kx8 chip instead of 8kx8 along with a 74LS08 as discussed earlier for making 32k RAM expansions with carts, you want have to have a switch to select BLK3 or BLK5 as you'll be able to cover all BLK 1, 2, 3 and 5.

Then you'd probably only need a switch for R/!W and maybe to disable the storage capacitor to prevent the content from transferring into flash at power down.

Also, concerning 3V/5V interfacing, since the VIC-20 recognises TTL level signals, it also perceives 3V cmos signals properly. The problem occurs when the VIC signals output CMOS 5V signal to CMOS devices powered at 3V.

Some CMOS devices are "5V input tolerant". In these cases, these 3V powered devices can be connected directly to the VIC's bus. Where 5V tolerance is not available, there is always the 74CBTD16211 as an option. If not, using a large bunch of 3.3k resistors with 3.3V zener diodes should do the job because of the very slow (compared to modern devices) dv/dt of the VIC on its address and data bus.

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hawk
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Postby hawk » Mon Jul 28, 2008 7:01 pm

I Had my two samples of the SimTek 12C68 arrive yesterday in the post. Now I just need to work out how to install them.

Brian, do you have a schematic that shows how you wired in the new nvSRAM chip?

Or is it really so basic , that it's not required.

There's a switch to go between Blk 3 and Blk 5, but do you also need a READ ONLY switch if you want to run original ROMs?

And a switch to stop write back...or is this the same switch as the read only?

Although now I have a Behr Bonz, and the MegaCart is on the way, what ROM I'll find that's not on one of those I don't know. :wink:

Then there's also the few components required around the nvSRAM.

I've opted for the 600mil wide chip, just to be difficult.

There's an interesting story about the nvSRAM chips. I requested them as samples, and put my company's name on the request, as that usually ensures that I get them. I then had a phone call from the General Manager of the local distributer...I should point out that I work for a large multinational company. I think he thoguht there was potential there to make the big bucks. It took some fast talking to explain that they were for a prototype hobby project, that would not have a requirement for more than 100 pieces if it ever made production! :oops:

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6502dude
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Postby 6502dude » Tue Jul 29, 2008 8:07 am

hawk wrote:Brian, do you have a schematic that shows how you wired in the new nvSRAM chip?


I do not have a schematic.
Have a look at the 8K eprom hack for some info.
The only addition beyond this is to add 10k resistor between pins 28 & 26 and adding 68uf capacitor between pins 1 & 14. The rest is just making sure that address lines from 2564 ROM layout go to correct pins on STK12C68.
If you get stuck, let me know and I will try to draw something.

There's a switch to go between Blk 3 and Blk 5, but do you also need a READ ONLY switch if you want to run original ROMs?

I only added the BLK3 / BLK5 switch (as suggested by NBLA000) for greater flexibility. This also provides ability to stop auto-start when you wish to write a new image to the nvram.

There are very few games which test for write capability. However adding another switch to hold /WE high should not be a big deal.

I've opted for the 600mil wide chip, just to be difficult.


I acutally intended to order 600mil version for testing when a bought some of them. I'm not sure if distributor screwed up or if I selected wrong part #. The 600mil chip will look much neater on the PCB when installed.
Image Mega-Cart: the ultimate cartridge for your Commodore Vic-20

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hawk
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Postby hawk » Tue Jul 29, 2008 5:38 pm

Thanks for that Brian,

I'm currently laid up in bed with the flu, but when I'm feeling up to it, I'll give it a try.

Just to confirm...the only reason that you didn't have to cut any tracks was because you used the 300mil chip, and didn't connect all the pins to the original holes. I'll have to complete the full 8k EPROM hack, including cutting tracks, because I'm mounting in the original holes.

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6502dude
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Postby 6502dude » Tue Jul 29, 2008 9:08 pm

hawk wrote:Thanks for that Brian,

I'm currently laid up in bed with the flu, but when I'm feeling up to it, I'll give it a try.


Sorry to hear that.
Get well soon!

Just to confirm...the only reason that you didn't have to cut any tracks was because you used the 300mil chip, and didn't connect all the pins to the original holes. I'll have to complete the full 8k EPROM hack, including cutting tracks, because I'm mounting in the original holes.


This is correct.
Some of the pins of the 300 mil chip are left raised above PCB and 30awg wire connects to these pins.
Image Mega-Cart: the ultimate cartridge for your Commodore Vic-20

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hawk
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Postby hawk » Thu Jul 31, 2008 1:03 am

Well I'm looking at this hack now, and I'm a bit confused.

Should pin 26 be connected directly to Vcc, or should it be via the 10k resister?

I think that I should have left pin 26 out of the original hole.

Also, do I need a cart that has the R/W line on the edge connector? If so, I think I'll have to start again. :cry:

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6502dude
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Postby 6502dude » Thu Jul 31, 2008 7:34 am

hawk wrote:Well I'm looking at this hack now, and I'm a bit confused.

Should pin 26 be connected directly to Vcc, or should it be via the 10k resister?


You need the 10k resistor between pins 28 & 26.

I think that I should have left pin 26 out of the original hole.

Yes, this is correct. You can also just cut the VCC trace to this pin and use wire wrap wire to route VCC to pin 28.

Also, do I need a cart that has the R/W line on the edge connector? If so, I think I'll have to start again. :cry:


Yes, you need R/W edgecard line for this cart hack.
I made same error as well on one cart :oops: , but I only got as far as desoldering old rom from PCB board.

I found that many Omega Race carts have all 44 edgecard connectors.
Image Mega-Cart: the ultimate cartridge for your Commodore Vic-20

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hawk
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Postby hawk » Thu Jul 31, 2008 7:43 am

Oh bugger! :cry:

I looked through my carts for ones with the extra connections on the edge connector, and most didn't have them. The ones that did seem to be the carts with the metallic label. I guess they're early ones, before the cost cutting really got started.

Unfortunately I don't have any of those ones to spare, so I'll have to wait until I come across some more.

It's almost worth getting a run of these boards done.

Anyway, thanks again for your help. Maybe I'll attempt to glue a contact in place. CA glue may work OK, if I can find some thin enough copper.

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carlsson
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Postby carlsson » Fri Aug 01, 2008 8:25 am

How about those pens you are supposed to use to restore broken lines? I've never seen or used one of those but would think it's up to the task to create one more line on the cartridge connector?
Anders Carlsson

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6502dude
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Postby 6502dude » Fri Aug 01, 2008 10:02 am

It may be a hassle, but it is better to desolder chip from existing board and start fresh on one with full edgecard.

Trying to glue a contact may just leave you with a defective expansion slot on your Vic-20 should the piece that is glued on come off and short out the edgecard or get jammed in socket.

I have never used the conductive pens, but my guess is that the material will wear off quickly (if it works at all).

Surplus Vic-20 carts can be bought for a couple of bucks. So, it is less costly in long run just to use one that has /W line on it.
Image Mega-Cart: the ultimate cartridge for your Commodore Vic-20

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hawk
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Postby hawk » Fri Aug 01, 2008 6:16 pm

That's good advice Brian...when you put the cost in perspective with the rest of the system.

The carts are not so frequent over here, but I believe that's the best option.

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hawk
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Postby hawk » Sun Aug 10, 2008 5:49 am

Sorry to bug you about this again Brian, but I have another question...hopefully the last. :wink:

I've now got a 1900020 Rev A board, so that I can access the R/W line on the edge connector. Now I just need to work out where it goes.

Does it go to Write Enable, or Chip Enable on the nvSRAM?

Could you help please?

Thanks.

BTW, I have a switch flipping between BLK3 and BLK5 to allow me to reload the nvSRAM.


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