Vmod your Radeon X800 for core, memory and overcurrent.

The general locations of mods:

Core voltage:

Connect a 10K ohms variable resistor to R1597 as shown, one wire to each end.

Set VR at 10K ohms, and it will give about 0.1v above default of around 1.33v.
Tune down VR to get higher volts.Measure VGPU from here:

For overcurrent protection mod when too much power is drawn and the card will
reset, Connect a 500K ohms VR to R1596 as shown and the other end to ground.
Original resistance of R1596 is 41k ohms so tune down the VR till the R1596
measures about 20K ohms.

Vmemory mod:

Measure default voltage from SMD capacitor point marked below.

Default is around 2v. Connect a 20K ohms VR to pin 5 of the chip marked above
and when set at 20K ohms, it will give around 0.08v above default. Tune down
VR for more voltage. I’ve used 2.09v so far and will be trying 2.25v soon.

Here’s pic of modded card.