Posted By
Ken
on 2018-05-18
14:36:29
|  c16 64k cartridge problem solving
Well, I have not played with my carts for a while due to my C16 hating them, and today I started tearing into the C16 to find the issue and fix it. Well, I found a down and dirty fix, but hopefully that will point me to a clean fix.
https://www.dropbox.com/sh/el9um7oeoh8wifr/AAABWCTEdCy4V4CwhFBCD5lTa?dl=0
Well, back to poking at the C16! 
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Posted By
Luca
on 2018-05-19
07:46:10
 | Re: c16 64k cartridge problem solving
So, are we close to an official Coprolite memory expansion?
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Posted By
MIK
on 2018-05-19
11:28:03
 | Re: c16 64k cartridge problem solving
Shame you don't have a Rev.B C16 to try as I'm sure it would work without any fix/mod.
Nice to see it works though! 
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Posted By
Ken
on 2018-05-19
13:08:41
| Re: c16 64k cartridge problem solving
Oh yeah, the Coprolite memory is ready
Made a nice fresh batch, just don't like the idea of it working on some and not others.
I will need to keep my eyes out for a dead rev B to repair, then figure out why the B works with no mod and the A is like me (loves being a pain)... lol
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Posted By
Rex/Camelot
on 2018-06-09
10:30:36
| Re: c16 64k cartridge problem solving
I would like to get a 64K cartridge working on my C16 REV.A without destroying pin 9 on the onboard memory. I have a https://www.pcbway.com/project/shareproject/OpenC16RamExpansion_V2.html cartridge by SukkoPera - which seems to almost identical to the coprolite cartridge memory-wise.
Does anyone know what non-destructive modification can be made to a Rev.A board to make the cartridge work? I would like to be able to unplug the cartridge, and have my C16 still work with 16K afterwards.
Alternatively, does anyone have schematics of the Rev.B? It would be interesting to compare it to the schematics of Rev.A to reverse engineer the changes they made in the hope of turning them into a modification for Rev.A.
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Posted By
Ken
on 2018-06-20
23:01:49
| Re: c16 64k cartridge problem solving
Yes yes yes !!!!!!!!..... OK, enough of that.
Today I had a few min to look over the issue, and the answer hit me like a ton of bricks (or should I say the answer was to NOT follow the data sheet for the memory, and instead do what C= loved to do: just wing it...).
With a bit of hacking on the cartridge ... the memory now works without hacking the C16.
It's 10PM and past my bedtime, but I will be back with some actual helpful info and pictures.
But for now... My batch of cartridges work as they should!
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Posted By
MMS
on 2018-06-21
01:25:26
 | Re: c16 64k cartridge problem solving
 Congrats!
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Posted By
Mad
on 2018-06-21
12:57:47
| Re: c16 64k cartridge problem solving
Wow!! Congrats!!!
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Posted By
Rex/Camelot
on 2018-06-24
05:33:23
| Re: c16 64k cartridge problem solving
Great. That sounds very promising!
I can't wait to hear what the trick is that prevents the crosstalk between the cartridge memory and the onboard memory.
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Posted By
MIK
on 2018-06-25
11:30:29
| Re: c16 64k cartridge problem solving
Ken,
You WIN!
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Posted By
MCes
on 2019-06-22
08:00:24
 | Re: c16 64k cartridge problem solving
Somebody told that the original project of C16/PLUS4 had a pin on cartridge for deselecting the internal RAM memory, and only this make possible to add a 64k RAM expansion on cartridge without cuts/desolder anything....
I found a PLUS4 schematic that indicate "Z" pin as "NC/(RAMEN)"
but the final revision don't have it.......
"RAMEN" could be interesting because it can deselect the internal RAM only when a ram cartridge is plugged, this let the 16K internal RAM operative when no cartridge is plugged: cut traces o removing RAM chips imply that C16 can't work without the ram expansion on cartridge...
Why Commodore didn't connect "RAMEN" is a mystery....
I made a theoretical schematic that implement "RAMEN" on C16 without new chips, but only using a pair of unused gates....
If somebody is a owner of a 64k expansion ram cartridge could try this little mod on C16 (see PIC), on cartridge the pin "Z" has to be connected with GND: if C16 is without cartridge it will work as a common C16, but plugging the cartridge it will be see 64k (without bus conflict...)
https://i.postimg.cc/yNT9GDBc/schema.jpg
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Posted By
Ramtop
on 2019-06-23
15:08:48
| Re: c16 64k cartridge problem solving
I remember Bil Herd saying he was ordered by management to make sure memory could not easily be expanded on the 264 machines with less than 64K because Commodore wanted people to buy the Plus/4, not get a cheaper C116, C16 or 232 and expand it.
Typical greedy C= decision.
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