ATI 4850/4870 voltmod thread

[dejanh]

Well, I just picked up a brand new Palid HD 4870 Sonic Dual Edition and I am trying to volt mod it. The voltage seems to be determined through a VID table and is controlled by NCP5388 (http://www.onsemi.com/pub_link/Collateral/NCP5388-D.PDF). The phase controller is located on the top side of the card, but it is connected to resistors on the back side arranged in two rows. The rows have 3+4 1k Ohm resistors soldered on in the top and bottom row respectively. These look to be pullup resistors however so I have no idea how VID is determined currently. Nothing seems to match the tables. Anyway, I took the DMM and measured the voltages to be 1.245V idle and 1.263V load. And that's about as far as I got. I managed to map connections on the bottom to the pins of the NCP5388 and they map as follows (I'm using the word bridge here to indicate the small section where two connected or unconnected solder points are where resistors could be added or are already present):

Pin 2 (VID0) maps to 1st set of bridges in both rows.
Pin 3 (VID1) maps to 2nd set of bridges in both rows.
Pin 4 (VID2) maps to 3rd set of bridges in both rows.
Pin 5 (VID3) maps to 4th set of bridges in both rows.
Pin 6 (VID4) maps to 5th set of bridges in both rows.
Pin 7 (VID5) maps to 6th set of bridges in both rows.
Pin 8 (VID6) maps to 7th bridge in the lower row.
Pin 9 (VID7) maps to the complete set of bridges in the lower row.

The pics of the card from the front and from the back are attached to this post (I took these from the web as my camera sucks for closeup shots)...

Help please