Is it possible to downgrade from 4mb to 1mb the Action replay 4m PLUS

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Hello
I just would like to know if it possible to turn this Action replay 4m plus to
a 1mb cartridge by single switch or removal of ram chip
Because it dosn t work , maybe one of the chips is corrupted that s why 1mb
would do it for me.
I can t find any DIY PCB layout on a saturn extension ram and how the
palcee22v10h communicante with the saturn .
 
you would have to change the code it sends to the saturn to stop saying 5C and start saying 5A. You would also have to cut the higher pin address lines so that it mirrors after 1MB. Hardly worth the trouble for the select few games that support it. Would be cheaper (both money and time wise) to replace the cart or replace the RAM on the cart.
 
thanks fo the reply knightofdragon
Changing the code sent to the saturn would require knowing the micro code on the pal plcc which i didnt knew until today that it is undocumented
and remain a mystery,if people knew they would have made their own ram extension cartrige and would t rely on the chinese action replay .
 
you would have to change the code it sends to the saturn to stop saying 5C and start saying 5A.
That's a single byte at the end of cart memory right? If the cart is flashable that seems easy...

The mirrored lines will affect games that use mirrored address. So maybe some games might work with just this. I don't know enough about mirrored lines.
 
That's a single byte at the end of cart memory right? If the cart is flashable that seems easy...

The mirrored lines will affect games that use mirrored address. So maybe some games might work with just this. I don't know enough about mirrored lines.
yes, need to find out how the cart sends the code at 0x24FFFFFF.

The official 1MB mirrors after the 1MB mark. Cutting the address lines to the anything 1MB and above will get you mirrored lines.
 
IIRC, the diodes D1-D4 are used to set either the ones or the zeroes of the cartridge ID (probably the zeroes, since the pins all have pullup resistors). The anodes are connected to the data lines, and the cathode is connected to a pin on the PAL.

But this modification won't help with anything. If the memory chips are fried in the regions not used by 1MB games, the 1MB games will run fine as-is. If the problem is in the area used by 1MB games, changing the cartridge ID won't magically fix that.

By rewiring the address MSBs you could change which physical addresses are mapped into the 1MB region, but the first task is to accurately diagnose the actual problem.
 
IIRC, the diodes D1-D4 are used to set either the ones or the zeroes of the cartridge ID (probably the zeroes, since the pins all have pullup resistors). The anodes are connected to the data lines, and the cathode is connected to a pin on the PAL.

But this modification won't help with anything. If the memory chips are fried in the regions not used by 1MB games, the 1MB games will run fine as-is. If the problem is in the area used by 1MB games, changing the cartridge ID won't magically fix that.

By rewiring the address MSBs you could change which physical addresses are mapped into the 1MB region, but the first task is to accurately diagnose the actual problem.
correct, the only thing changing ID is going to do is prevent any 4MB games that do not check for 1MB.

Forgot also that you would need to change the addressing even further, since on the 1MB cart the banks are not contiguous.
 
Thanx for your help guys
In the beginning i though that the scene did already figure the logic behind the pal plcc mirroring and a diy Ram extension cartridge had already been made .
So best thing to do in my case is to locate the fried one and find a spare one those damn old ram are notorious for breaking down and also the fact that manifacturer in china are reusing old unreliable chips
 
It happened to a friend of mine, he had a version 2 chip ali express.

He had to save his cartridge with some Epprom.. I'm trying to remember..
This caused the failed chip to start again.
 
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