Resistances of V-Core and V-RAM for AMD Radeon RX 6900 XT

[AllElectronicsRepairs]

Hi Guys, what should be the resistances to Ground of V-Core channels and V-RAM for AMD Radeon RX 6900 XT? Is 67.9 mOhm for V-Core OK? I am trying to diagnose this Graphics Card and check for any shorts first. Like none of the power rails seem to be shorted, but I want to make sure before injecting any (low) voltage to see if any component raises its hand... Kind regards, Jerry..

[FriedFred]

It's quite difficult to diagnose a short at a CPU or GPU. There are thousands of transistors in parallel, this keeps the "ON"-Resistance very, very low. So, usually, with a standard-multimeter, it's not possible to make a correct diagnose on a CPU or GPU. I have had "dead" GPUs and they worked just fine after removing of the real short maker...
You can diagnose a short with a controlled electrons injection also at CPU and GPU core level. Those cores use a voltage up from 0,65V. So if you use a voltage not higher than 0,5V, all is nice in this delicate areas. If you have a short or at least a higher current consumption with this low voltage, then really something is wrong.

[DynaxSC]

To measure VCORE resistance on a GPU u need a milliohm meter. It has a slightly different design compared to a standard DMM and uses 4 wires from meter to probes (2+2). So it is able to compensate the wire resistance when measuring very low resistances. I'm not sure what should be the resistance for a RX6900XT, but for a healthy GTX1070 it is in the range of 150-200 mohm. You can buy some milliohm meters on AE, and they are affordable and do the job. Anybody dealing with GPU repair I'd recommend to have one, as it helps to check GPU very easy and fast.

If you have a high quality DMM with a very high resolution (4 or 5 digits), u might also do two measurements, first the GPU resistance, second the probe short resistance, and then substract from the GPU resistance the probes short resistance to get the real GPU resistance. However normal DMM's have a too low resolution as they can measure usually not better than in 100 mohms steps, so not enough to have a qualitative result.

[AllElectronicsRepairs]

To measure VCORE resistance on a GPU u need a milliohm meter. It has a slightly different design compared to a standard DMM and uses 4 wires from meter to probes (2+2). So it is able to compensate the wire resistance when measuring very low resistances. I'm not sure what should be the resistance for a RX6900XT, but for a healthy GTX1070 it is in the range of 150-200 mohm. You can buy some milliohm meters on AE, and they are affordable and do the job. Anybody dealing with GPU repair I'd recommend to have one, as it helps to check GPU very easy and fast.

If you have a high quality DMM with a very high resolution (4 or 5 digits), u might also do two measurements, first the GPU resistance, second the probe short resistance, and then substract from the GPU resistance the probes short resistance to get the real GPU resistance. However normal DMM's have a too low resolution as they can measure usually not better than in 100 mohms steps, so not enough to have a qualitative result.

Thank you for your reply. Yes, I do have a milliohm meter and Kelvin probes (4 wire probes) that eliminate the need to measure wires resistance. I am pretty experienced electronics repairer (8 years) but modern graphics cards are NOT my usual repair devices. That is why I asked a SPECIFIC question, hoping for a SPECIFIC answer from somebody, who knows.

A tak poza tym, gdybyś przeczytał uważnie mój post, dowiedziałbyś się, że byłem w stania zmierzyć 67,9 miliohms, więc muszę mieć możliwość dokładnego pomiaru tak małych oporności. Ale dzięki za odpowiedź - i tak jestem wdzięczny. Pozdro, Jarek.

[DynaxSC]

Hejka, miło poczytać coś po polsku, i to z tak daleka. Pozdrawiam. Czarek.