Need help with an odd design construct

Having picked up one of these little TI Compact Computer-40 (cc40) units over the Summer, I thought I'd work on reverse engineering a RAM cartridge for the unit. As shown on this forum: http://atariage.com/forums/topic/255728-the-compact-computer-40-cc40/?p=389… The design *appears* to havea? "floating" ground when powered off battery alone.? The cartrridge edge connector has 2 grounds.? I didn't think anything about them at first, assuming they were connected to each other. Hwoever, someone with a RAM cart is helping me reverse engineer, and it appears pin 1 ground is connected to the RAM GND pin, but is connected via a 6K8 resistor to the 3V battery ground, which is connected to pin 27 ground line. I *assume* this means that, once the cart is pulled, the battery voltage sits somewhere in the middle of the 5V swing the RAM needs to see, but I can;t figure out how one calculates the voltage divider value for the inherent resistance of an SRAM, as the 3V is sent through a germanium diode (bringing the effective Vcc of the SRAM to 2.7V), and then SRAM ground is sent through the 6K8 to battery ground. Obviously, reverse engineering being fraught with errors, we could be wrong, but assuming not, what is going on in this circuit, and how does one calculate the effective potential of the GND pin of the SRAM? Pics: http://www.go4retro.com/downloads/CC40RAM/ Jim -- Jim Brain brain at jbrain.com www.jbrain.com