CPU swap creates memory issues Gigabyte AM5 B650

[kirbyrj]

I've been using a Gigabyte B650 Aorus Elite AX for the past several months with a 7700x. I have a set of Corsair DDR5 6600 (2x16GB, SK Hynix). I don't have the box for it in front of me, but I'd bet it's regular XMP Intel stuff (non-EXPO). I historically would set XMP settings in BIOS. Downclock the speed from 6600 to 6200 and set the memory divider to 1:1 and leave the XMP timings in place. I have had zero issues doing this for as long as I've owned this setup.

Today, I swapped in a 7800X3D to try it out. It wouldn't boot at my old settings...no big deal. Reset the bios and re-enable XMP and change the speed from 6600 to 6000. Won't boot. I gave it at least 15 minutes to "memory train" but it never got off the CPU LED (when doesn't always indicate a CPU issue as strange as that sounds). If I enabled XMP, no dice... So I just went in and changed the speeds to 6200, 1:1, and all the timings to the same as would be in place if I had XMP enabled and it boots fine. Memory training was done in less than a minute.

Is this normal to have that much variation in ONLY the XMP setting when switching CPUs on AM5? I've only built two AM5 setups, but I've never had an issue like that. Is it a motherboard issue? I know the Gigabyte B650 boards have been known to be a little finicky with memory ( at least according to reddit...and reddit is about as useful as Newegg reviews back in the day).

 

[learners permit]

You could set XMP and change the mem speed and the boot order to a bootable flash drive with memtest to investigate whether the board reverts to the actual XMP settings on the spd chip. That would show if it's a bios bug at least so it could be reported to the vendor for correction. Crap never mind it won't post so forget this reply.

 

[Nobu]

CPU's in there good, mounting pressure even, no bent pins?

 

[kirbyrj]

CPU's in there good, mounting pressure even, no bent pins?

After the first few times it wouldn't boot, I unmounted everything and checked. Running it with an AIO. The paste was even and there were no bent pins. I almost swapped in the old CPU just to check it, but I'm in the process of selling it and I didn't want to unpack it.

 

[kirbyrj]

I don't get it. I'll just have to remember the timings off the top of my head when it comes time to update the bios.

If I get time to play around, I'm going to enable XMP and then set it to 4800 and see if it will boot. I just find it strange that simply enabling XMP causes it not to boot, especially since it worked fine with the last CPU.

 

[bitnick]

I'm certainly no expert on RAM timings, but aren't there settings for refresh (tREFI, maybe others?) that could need to be reduced if the frequency is reduced, to avoid too long period between refreshes? I.e. say the refresh period should be 7 µs (46200 cycles at 6600 MHz) then maybe that value should be changed to 42000 at 6000 MHz (46200×6000/6600) to avoid too infrequent refresh.

Just an idea, maybe it's inconsequential. But in general, if I were to run 6600 MHz mem at 6000 MHz, I would use a spreadsheet to recalculate the timings to fit, i.e. to keep the absolute timings constant.

 

[Azrak]

Did you flash the latest BIOS? Newer BIOS might have better support for 7800X3D.

 

[kirbyrj]

I'm certainly no expert on RAM timings, but aren't there settings for refresh (tREFI, maybe others?) that could need to be reduced if the frequency is reduced, to avoid too long period between refreshes? I.e. say the refresh period should be 7 µs (46200 cycles at 6600 MHz) then maybe that value should be changed to 42000 at 6000 MHz (46200×6000/6600) to avoid too infrequent refresh.

Just an idea, maybe it's inconsequential. But in general, if I were to run 6600 MHz mem at 6000 MHz, I would use a spreadsheet to recalculate the timings to fit, i.e. to keep the absolute timings constant.

I'll have to look into this more. Thanks for the insight.

Did you flash the latest BIOS? Newer BIOS might have better support for 7800X3D.

Yes, I'm on the newest beta. Something like F22b on this board.

 

[chameleoneel]

I've been using a Gigabyte B650 Aorus Elite AX for the past several months with a 7700x. I have a set of Corsair DDR5 6600 (2x16GB, SK Hynix). I don't have the box for it in front of me, but I'd bet it's regular XMP Intel stuff (non-EXPO). I historically would set XMP settings in BIOS. Downclock the speed from 6600 to 6200 and set the memory divider to 1:1 and leave the XMP timings in place. I have had zero issues doing this for as long as I've owned this setup.

Today, I swapped in a 7800X3D to try it out. It wouldn't boot at my old settings...no big deal. Reset the bios and re-enable XMP and change the speed from 6600 to 6000. Won't boot. I gave it at least 15 minutes to "memory train" but it never got off the CPU LED (when doesn't always indicate a CPU issue as strange as that sounds). If I enabled XMP, no dice... So I just went in and changed the speeds to 6200, 1:1, and all the timings to the same as would be in place if I had XMP enabled and it boots fine. Memory training was done in less than a minute.

Is this normal to have that much variation in ONLY the XMP setting when switching CPUs on AM5? I've only built two AM5 setups, but I've never had an issue like that. Is it a motherboard issue? I know the Gigabyte B650 boards have been known to be a little finicky with memory ( at least according to reddit...and reddit is about as useful as Newegg reviews back in the day).

Its likely there are some sub-timings from the XMP profile which the board and/or CPU doesn't like. And when you manually enter some timings, those sub-timings aren't being entered by you. And the CPU instead auto trains those timings.

This post has my complete timings for my 7800X3D, at 6200. These timings are based on Buildzoid.
https://hardforum.com/threads/anyon...x3d-to-7800x3d.2027175/page-5#post-1045832961

I was able to get away with some pretty low voltages, as my RAM is a DDR5 7200 kit. You may need higher voltage. I would start with 1.4 or 1.45. Get the timings stable. And then tune down the voltage, if you can.

 

[kirbyrj]

Its likely there are some sub-timings from the XMP profile which the board and/or CPU doesn't like. And when you manually enter some timings, those sub-timings aren't being entered by you. And the CPU instead auto trains those timings.

This post has my complete timings for my 7800X3D, at 6200. These timings are based on Buildzoid.
https://hardforum.com/threads/anyon...x3d-to-7800x3d.2027175/page-5#post-1045832961

I was able to get away with some pretty low voltages, as my RAM is a DDR5 7200 kit. You may need higher voltage. I would start with 1.4 or 1.45. Get the timings stable. And then tune down the voltage, if you can.

Thanks I'll give it a look.