PRIME X370-PRO: effectively lost 2 memory slots after BIOS update

[X370-Bro]

I recently updated the BIOS on my PRIME X370-PRO board with a Ryzen 7 1700X installed from version 5603 to 5606. During the process I experienced an inability to POST issue which I eventually diagnosed as an unexpected reduction of support from four DIMMS down to two. Following is an account of the process up to this point.

I normally update BIOS through ASUS' online updater, but the update to 5606 did not appear. Instead, I used a USB drive with the relevant payload. The update itself went as expected until the auto-reboot portion, which produced a black screen. I waited approximately 15 minutes in case the issue was an unexpectedly long retrain period or something similar before manually resetting. Restarting produced the same result: black screen, no POST. It seemed to otherwise behave normally up until the point of POSTing: fans spun on powerup, and the system responded to CMOS clear.

This kind of issue initially suggested CPU incompatibility. I've never heard of a 300-series board dropping support for first generation Ryzen after a BIOS update, but I investigated anyway and found no information. The original note of Windows 11 support was all I found.

The board does not include Dr. Debug but I do have a PC speaker installed. I started pulling various things to see if I could get at least some audio feedback: the USB drive with the BIOS file, the boot SSD, and all the DIMMs. The last one finally produced audio feedback. I re-installed one DIMM into the second slot, and the system finally booted. I shut down and installed a second DIMM into the fourth slot, and again the system booted. Upon adding a third DIMM, the system reverts to the initial problem state: black screen, no POST. Same with four.

I figure at this point I should revert to the previous BIOS version. However, upon doing that, the issue remained. No matter what I try, I can no longer boot with more than two DIMMs. It doesn't matter which slots are occupied. The system boots with just two DIMMs whether they're in, say, slots 2+4 or 1+2. Add a third DIMM anywhere, and it stops booting. Same with all four. I've shuffled the sticks around enough times where I'm confident the issue isn't that one or two of them are bad. Furthermore, they've been tested recently.

I had the thought that perhaps the IMC had suddenly degraded (even though it was previously running at just 0.93750V), so I set SoC to 1.1V and set RAM to 1.35V while two DIMMs were installed and then attempted to add more. At this point the system was otherwise running with CMOS defaults, so RAM would be running at its JEDEC specifications. No luck.

Here is the SPD data of one of the modules reported by Thaiphoon Burner; all four DIMMs are the same:

-------------------------------------------------------------
                         MEMORY MODULE
-------------------------------------------------------------
Manufacturer             : Crucial Technology
Series                   : Ballistix Sport LT Gray
Part Number              : BLS8G4D30BESBK.8FD
Serial Number            : E1A46F4Fh
JEDEC DIMM Label         : 8GB 1Rx8 PC4-2400R-UA1-11
Architecture             : DDR4 SDRAM UDIMM
Speed Grade              : DDR4-2400R
Capacity                 : 8 GB (8 components)
Organization             : 1024M x64 (1 rank)
Register Manufacturer    : N/A
Register Model           : N/A
Manufacturing Date       : October 1-5 / Week 40, 2018
Manufacturing Location   : Boise, USA (SIG)
Revision / Raw Card      : 0000h / A1 (10 layers)
-------------------------------------------------------------
                        DRAM COMPONENTS
-------------------------------------------------------------
Manufacturer             : Micron Technology
Part Number              : D9TZV (MT40A1G8WE-075E:D)
Package                  : Standard Monolithic 78-ball FBGA
Die Density / Count      : 8 Gb D-die (Z01B / 20 nm) / 1 die
Composition              : 1024Mb x8 (64Mb x8 x 16 banks)
Input Clock Frequency    : 1200 MHz (0.833 ns)
Minimum Timing Delays    : 16-16-16-39-55
Read Latencies Supported : 24T, 23T, 22T, 21T, 20T, 19T, 18T...
Supply Voltage           : 1.20 V
XMP Certified            : 1502 MHz / 16-18-18-38-69 / 1.35 V
XMP Extreme              : Not programmed
SPD Revision             : 1.1 / September 2015
XMP Revision             : 2.0 / December 2013

Click here for Micron's product page.

Unfortunately I do not have access to an alternative set of 288-pin DIMMs at the moment, nor do I have access to another motherboard that accepts four full size DDR4 modules. Therefore testing alternative configurations will be challenging at the moment. If I have to make a choice between Windows 11 support and access to all four DIMMs, I want the DIMMs, at least for now. If at some future point I want to move to Windows 11 and need to deal with access to only two slots, I'll make that decision then. Thanks for any assistance rendered.

[STARRAIN_ROG]

Hi X370-Bro,

Do you mean you have revert to BIOS 5603, but it didn't boot with four DIMMS as well?
Have you also tried one stick in slot3, and it boot successfully?
Thank you.

[X370-Bro]

Thanks for the reply. Yes, I did mean that when I downgraded from 5306 to 5303 that it also wasn't booting with four DIMMs. I've gotten it working while gathering test data. I'll detail my subsequent findings in case this issue comes up again with someone else.

Since my original posting I re-flashed from 5303 to 5306 for more testing against the newest version. I tested all 15 possible combinations of 1 to 4 sticks installed and verified that all 10 combinations of 1 and 2 sticks POSTed. Meanwhile all 5 combinations of 3 and 4 sticks failed to POST. During this testing BIOS settings were at their defaults with the exception of the clock being set to current time and disabling the throbbing RGB feature of the board.

My next step was to run the same testing process against 5603, but, surprisingly, upon downgrading a second time, four sticks now works. I am currently verifying proper operation, but it appears to be working normally. At this point I'm inclined to remain with 5303 and consider 5606 incompatible with my setup. Thanks again for the reply.

[STARRAIN_ROG]

Hi X370-Bro,

Since I haven't received the same feedback from other user, if there is a chance to update to 5306, could you please check it again?
Thank you.

[X370-Bro]

As suggested, I again flashed from 5303 to 5306, with all four DIMMs installed and with a difference being that I reset to BIOS defaults before flashing. This time the process did not hang on a black screen upon the reboot attempt at the end of the flash and instead POSTed without issue. Full RAM capacity was represented, and the system seems to work normally.

[STARRAIN_ROG]

Hi X370-Bro,

Thank you for your update.
If there is any questions, please let me know.