Reply 40 of 64, by PC@LIVE
snufkin wrote on 2021-05-16, 21:37:PC@LIVE wrote on 2021-05-16, 21:06:
Ok I checked. From a quick check the PIN A21 of the PCI and the PIN6 of the RAM are not connected. But the PINs are not very acc […]weedeewee wrote on 2021-05-16, 20:31:
maybe check between pin 6 of sdram and pin A21 of pci to see if connected .
Ok I checked.
From a quick check the PIN A21 of the PCI and the PIN6 of the RAM are not connected.
But the PINs are not very accessible, I'll do another check from the back of the motherboard as soon as possible.
For the moment I have not done the PIN checks of the RAM, and I have to finish those of the PCI.
I don't know if it applies to this motherboard, but I know at least one (Abit KA7) where the RAM voltage supply is switched between the board's common 3.3V regulator (comes via the ATX 12V) and a separate 3.3V supply from the ATX 5VSB (for standby mode support). So for that board the RAM Vdd isn't directly connected to other 3.3V pins.
Still, all these 3.3V pins have to go somewhere.
Ok thanks for the info.
I had time today to do some checking. regarding the RAM I have identified where the + 3.3V PINs go, I didn't have time to check them all, those of the final part of the DIMM (PIN 73 84 157 168) go to PIN3 of Q4.
At this point I think it is useless to check the rest of the PINs, also because the RAM will be powered by the Q4 PIN3 (+ 3.47V measured).
Another check I did is the one on the other mosfets, in practice four are powered directly from the power supply, the current comes directly from the + 5V (red wire), and these are Q8 PIN2, Q22 PIN2, Q4 PIN2, Q7 PIN3.
The Q6 PIN2 is directly connected to the Q8 PIN3, the current measured between these PINs is about 1.85V.
At this point I miss to check the BXX side of the PCI slot, currently I have not yet identified where the + 3.3V current can come from, and I think it is essential for the functioning of the PC, but I'm not sure about this.
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