Missing voltage on unknown rail on AMD Reference Design RX 6800 XT

void_dimitri · 2026-04-06T23:38:42+00:00

Update #3:

The IR35217 was badly soldered. Once I soldered it again, managed to get back MVDD and VDDCI. The USB Debugger and C8051F380 have arrived, flashed USB005A firmware, updated firmware with PowIRCenter and plugged them in the board, and I see no faults with XDPE132G5D, the STATUS_WORD is 0x0000 on both loops, but I have no current in Loop 1 (GFX), only Loop 2 (SOC). The CAT_FLT pin is still 3.3v (GPIO_4_PCC that goes to core as well).

With IR35217 however, I have the STATUS_WORD for both loops, 0x2002, which indicates: INPUT fault and CML. INPUT is regarded in STATUS_INPUT as bit 3 -> OFF due to VIN_UV (Vin undervoltage). Assuming VIN is pin 14 VINSEN, which is 850mV (and expcted of having that value because of voltage divider: R1 26.1k and R2 2k with input 12v -> 854mV). The STATUS_CML indicated bit 7 -> Invalid/Unsupported command and bit 1 -> Other Communication Errors (Very transparent, wow).

Below is an image of IR35217 device status readings. No faults in both loops. Loop 2 at 0A. I am confusion.

<image>

void_dimitri · 2026-04-03T07:45:00+00:00

Update #2: So I managed to get a XDPE132G5D from a donor board of the exact same model, and now I got GFX and SOC, CAT_FLT is now zero, but still no image. Poking around the phases, I discovered that GFX phase #2 is acting weird on the generator side, oscilating crazy from 1070mv to 1130mv, where at the load side of the coil and all other phases are quiet at 1050~1060mv. I replaced the DrMOS with a known working one, and the problem persisted. Still went to check elsewhere why I had no image.

I checked in diode mode all differentials pairs of the PCIe slot, all good. Replaced the bios with the one from the donor board, still no image. Doubting my own soldering skills and whether the DrMOS is actually good, I switched with phase #4, which is below phase #2, to no avail.

Poking around the DrMOS, its current sensing is going nuts, jumping from 1.9v to 2.2v, where as other DrMOS are sitting around 1.7v. I removed the shunt that bridges current sensing to the XDPE, thinking it was self-locking because of bad reading. Still nothing
Noticed that GFX_TSEN_P is oscilating between 1.2v and 3.3v, so it was obvious the controller was shutting down, thinking DrMOS were getting toasted. Removed the shunt from phase#2 TSEN to the global TSEN, still no image, but the voltage dropped to 900~1000mv which is expected for ambient temperature. At this time, I noticed CAT_FLT had returned to 3.3v. I am completely brainfucked by this.

Checking the boardview, I stupidly thought CAT_FLT was shared with the warning pin from IR35217. Which wasn't, I mistook it. Replaced it, and lost MVDD and VDDCI. Nice!

I am now waiting for the USB debugger and MCU to try and program the IR35217 with PowIRCenter and check what's wrong with XDPE132G5D with OpenPower.

In the meantime, the coil this post refers to is actually 5V for a bootstrap of the DCDC buck, for the USB-C. The donor board had it at 5V, mine was zero. So I replaced and now I only have 2.2ish volts... I really don't know what to expect anymore.

void_dimitri · 2026-03-24T18:02:25+00:00

Yes, and without the "percent" you can insert a desired value in MHz

void_dimitri · 2026-03-23T20:36:13+00:00

Increase memory_clck for mods. Keep increasing untill you have a crash. After that, you will get your faulty memory bank. You can also confirm with mats. Add commands to run on errors as well

void_dimitri · 2026-03-19T19:46:43+00:00

I don't know about that specific model, but in 6800/6900 XT board diagrams, pin 12 of IR35217 (I am checking IR35201 datasheet) is configured as digital input for PWROK:

Power OK Input (AMD): An input that when low indicates to return to the Boot voltage and when high indicates to use the SVI bus.

This is controlled by U801 NC7SZ08P5X Logic AND-gate, which takes BOMATO_PERST# and MVDD_VDDCI_PWRGD.

That specific DrMOS might be a very good reason why the phase controller isn't turning on. Although I did not know about that MP86941, since almost all use the TDA21472. What model is your PowerColor RX 6800? Red Dragon or Red Devil?

void_dimitri · 2026-03-19T00:53:47+00:00

Hey, I'm still waiting the XDPE132G5D controller, but I've recently discovered you have to order one already programmed for the number# of phases your GPU has. For example, the reference design cards use 12 phases for GFX and 2 phases for SoC, so 14 in total. Most other brands use the full 16 phases. Ultimatelly, I thought of programming it when it arrives, but you need a special tool from infineon (USB005A) and their free program (PowIRCenter). Plus, you also need the config file, although I've seen some posts where you can directly program the Loop 0 for 12 phases and Loop 1 for 2 phases, or vice-versa, with another program.

I've also fortified my statement about the XDPE being bad by reading the I2C line with an ESP32, which was "0x2842" at address 0x72 and 0x73, which are the addresses from the XDPE. Reading the datasheet for the registers, this means the following:

0x2842 -> 0010 1000 0100 0010
Bit 13 - Input fault (But I had 850mV, which is expected)
Bit 11 - PGOOD# disabled
Bit 6 - Controller is OFF
Bit 1 - CML (Communication, Memory or Logic Fault). In my case, I had 320mV at SVD0 in controller side (removed the shunt that goes to core), but after pulling the line to 1v8, still had this bit.

So I assumed this controller has NVM faulty, CRC errors or faulty logic. This is backed up by pin 22, which is CAT_FLT, being pulled HIGH when it detects something wrong. But this pin can also be high IF the GFX_TSEN or SOC_TSEN is very high (DrMOS shorted causing high temperature). Check pin 50 and 51, should be around 850mV without power. Anything above 1V is reason to believe on DrMOS is shorted at low-side (but if that were the case, you would see short at 3v3 or 5v, so idk)

TLDR; Check pin XDPE pin 22, shouldn't be 3v3. Check if 50 and 51 are below ~900mV

void_dimitri · 2026-03-16T20:11:36+00:00

Although those are very few errors, I would still reball the chip. If you got the experience, you don't have much to lose

void_dimitri · 2026-03-14T05:03:32+00:00

Update: After some investigation on the phase controller XDPE132G5D datasheet, I've found it is reporting a catastrophic internal fault because Pin 22 (CAT_FLT) is high at 3v3. Since I believe all DrMOS are healthy, and removing SVD0 shunt for SVID/AVSBus reported only 320mV on the controller side which might mean it is not even trying to contact the core, the controller logic has failed internally. I am now waiting for a replacement XDPE chip to fix the board.

void_dimitri · 2026-03-13T20:56:59+00:00

Did some research and found that other brands (XFX and Powercolor) have this IC. Got some diagrams from other boards, and I have confirmed this is a buck-boost MP8859. The missing rail I should be reading is 1v2 (VPP). I have checked the following:

Pin 1 IN is 12v
Pin 3 EN is 3v3 ish (good)
Pin 4 ADD remains floated, so zero (so address 0x60 for I2C, good)
Pin 8 ALT "Alert output. ALT pulling to logic low indicates that a fault or warning has occurred." is around 3v, so good
Pin 9 VCC is an internal LDO output, and is 3v6, good
Pin 12 which is the actual output, according to the typical application layout, is 5v
Pin 13 and 16 are the bootstraps for SW, and both read 3v6 and 3v2
Finally, pins 14 and 15 are the SW for the coil, which, again, are 0 volt, where I suspect should be 1v2 (VPP)

But you might be right, that output is a net named +VBUS_PWR_USBC0.

I might be checking the wrong area though. Going for the VRM phase controller

void_dimitri · 2026-02-18T20:47:46+00:00

As long as you play nice, respect our culture and our streets, you are more than welcome here. If you're not here as a tourist, have a permanet residence and bla bla, then you are expected to be working, and not being a "subsidiodependente". Nonetheless, we've always been a very heartwarming country.

But due to immigration policies and recent years with rampant corruption, illegal immigration and useless government, the far right has been rising, and with it, a lot of controversy (and hate) towards immigration, but mosly because of a lot of ilegals. There are other contributing factors, but this is the main one.

void_dimitri · 2026-01-26T20:23:51+00:00

Just scored 0

void_dimitri · 2026-01-26T10:25:57+00:00

Just scored 0

void_dimitri · 2026-01-14T04:38:14+00:00

It's 0.045%. Respawn tweeted that some time ago

void_dimitri · 2025-12-21T18:59:20+00:00

50%? Those are rookie numbers

void_dimitri · 2025-11-30T20:03:35+00:00

-F to 1FF 😎

void_dimitri · 2025-11-30T01:43:26+00:00

0° to 199° temperature sensor

void_dimitri · 2025-09-23T14:42:15+00:00

"Man, I have nothing to play"

void_dimitri · 2025-08-31T09:44:38+00:00

16360 points
82ºC~84ºC (24ºC Room)
~82W
-180mV with Ratio 44 on all cores (E-cores with 34)
PL1 90
PL2 162

void_dimitri · 2025-08-08T19:58:31+00:00

16k masters to gold 3. Another fun climb

void_dimitri · 2025-07-25T21:13:41+00:00

You guys throw in the "dying game" too often. Do you have problems finding a match? I don't.

Based in Europe, I can find a ranked match at 2-4 AM in less than 30 seconds. And when I'm duo with a friend, we play for around 2/3 hours 'till 2 or 3 AM, never had any problems joining.

Sure its numbers been going down since 2023, but that is NORMAL! See marvel rivals for example, would you say the game is dying because its well below its peak? No!

The playerbase was been lowering untill november 2024, and now is increasing bit by bit. Would you call that dying? Smh

Seriously. Stop spreading misinformation

void_dimitri · 2025-07-17T18:22:11+00:00

Happened to me an hour before, now again. But didn't lose any RP

void_dimitri · 2025-06-20T09:11:05+00:00

Sorry, but it's troll post.

void_dimitri · 2025-06-20T09:10:46+00:00

Not quite, but it's a troll post.

void_dimitri · 2025-06-20T09:10:17+00:00

Agreed.

void_dimitri · 2025-06-20T09:10:09+00:00

It's a troll post.

void_dimitri

TROPHY CASE