[RoG Ally] Fault in one of the onboard RAM chips. Any way to diagnose which?

[Prott]

Hello dear badcappers!

The title pretty much says it all - do you, please, know if there's any way to troubleshoot which of the integrated RAM chips (LPDDR5X in this case) is faulty?

Backstory:
After replacing the 4 onboard (soldered) memory chips on a RoG Ally (4x4 GB to 4x8 GB) it got stuck on the RoG logo. I assume one of the chips is either not soldered properly or faulty. However after reflowing and replacing bunch of them I am still stuck at the same place.

If there is a way to narrow down which memory module is faulty it would make my life much MUCH easier.

Thank you.

[the Benninger]

I assume that the BIOS does not map the new memory the addresses are not the same, so I should make an arrangement in the BIOS, if the memory was in flat it would not generate any images

[Prott]

Thank you! However that should not be the case - multiple guides state that there's no need to change the BIOS for the console to boot. You have to only change the bios if you want to use the whole 32 GB and not just 16.

As for the logo - it's stuck at the first logo that displays immediately upon turning on the device. That logo does not come from the actual iGPU. I am not sure how it is done in case of Ally, but for example on Microsoft Surface it is stored in the screen itself and activated by a signal from SAM. The CPU can be completely dead and the logo will still show up.

[the Benninger]

Understood some manufacturers of phones and tablets use this method, they put the logo on a preboot, you are sufficiently informed apparently I will help you to investigate a little

[Prott]

Thank you! Did you have any luck?

From my additional research it seems like Zen 4 requires all four LPDDR5 modules (4x32 bit bus) for it to function, so I can only assume there's no way to run any code without all four modules working. Is there any other way to narrow down the faulty module? Anything I can probe with a scope? Thank you so much for any help.

[the Benninger]

hello it is good to be here again i found a straw with a great tutorial where they explain how to make the modification you want with sandpaper and detail, it seems to me that the detail is in the number of part of the memory that you want to install, give a view or hope this can lead you to conclude your project

https://allymods.com/ram-upgrade/

[Prott]

Thank you. Yes, I was following this guide - I even contacted the person who created it, but his conclusion was that one of the modules is probably faulty. Now I have to somehow check which one.

[the Benninger]

The truth makes sense, it was a pleasure to be able to help, let me know if you successfully concluded your work, greetings

[Prott]

So I managed to make it work. It was, I assume, my mistake in my BGA soldering technique - I underestimated the need for the gentle nudge once the solder is liquified and a proper cooling of the board post-reflow. Once I cooled the board (and chips) down with maximum airflow and minimum temperature the console works. I think not cooling the chips properly made them contract in a different speed than the board and thus they "tore" away from the board after reflow. Fortunately no pads were harmed

PS: After I switched the new 32 GB APCB data in the bios all works correctly. Too bad there's no strap configuration for 8 GB modules.