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Odd observation of Genesis Game Cart


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I was changing out the battery on a Genesis/MD cartridge when I discovered something that has me baffled. I cannot readily explain it, so I figured I'd post the information here and see if anyone else may be able to shed some light on the reasoning for the design.


So the cartridge in question is a EA Madden 95 board, version P10002 Rev M. On the SRAM's VCC line (ie, From the battery backup circuit) there is a decoupling capacitor in parallel with a 2meg resistor to ground. The particular SRAM is the Goldstar GM76C88ALK, and the capacitor seems to be a radial 100nF.


Now per my reading of the datasheet, the Goldstar SRAM has a standby current of about 2uA. Obviously there would be some small bleed from the capacitor. However, the Resistor would also have a current bleed to ground of around 2uA. Obviously the current leakage through the capacitor would be nothing of major concern, I question the reasoning of the resistor.


Is there something I'm not catching here, or is it as if EA wanted the batteries on these boards to eventually die? Maybe this was in an attempt to be able to sell the upcoming games, since the old game may prematurely loose power from the battery? The only logic I can see with this particular resistor is for the purpose of slowly bleeding the battery. Or is there something about the 1026B battery backup circuit that is clunky without this particular resistor?


I opened up a traditional Genesis cart, ESPN Speed World - PCB is 171-6278A, and notice that there is absolutely no resistor to ground. Considering that it is using the same GM76C88ALK and has a very similar battery backup circuit (BA6162), I see no real purpose for the 2meg resistor other than those of malicious intent.


Any thoughts?

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