jt has the right of it.Do the Q605/LC 475 boot w/o the DRAM on the MoBo?
From what trag has said about the limitations of the second SIMM in the 605 and the 630, it makes me wonder if the Mobo RAM is excised these machines might be able to address the full theoretical loadout using the four full capabilities of double banked SIMMs. It appears to me that the MoBo RAM is set up as a hobbled replacement for the first(second?) bank of the extra SIMM and that doing away with the MoBo DRAM ICs might free up those control lines for use on the unaddressable bank of the additional SIMM?
It's still and "under the board" PCB Hack, but what the heck!?! [}] ]'>
If you absolutely want to stick to chips which will fit in the 20 pin spots already on the logic boards, then yes, you are limited to 4MB total.
However, if you are willing to rig up additional connections, then you should be able to go up to 64 MB or possibly more. But this will be messy with wires and/or additional boards involved.