Built myself high end system in March for video/audio recording/editing/rendering. Also came in useful for MSFS that I started using this year.

It ran great, I updated to latest BIOS 2 months back and still ran pretty well but not great. Not poorly enough to mess around with it as very stable but enough to annoy me now and then that SOMETHING wasn't optimized.

Then I read article randomly stating BIOS/UEFI upgrade will RESET/DISABLE XMP profile.

Cue face palm....I tested my system with Performance Test (free from MS Store) and noted all tests were in 97-99% percentile EXCEPT memory at 75%. Hmmmm

Went to UEFI and yup XMP was NOT enabled! So I enabled it , rebooted, ran tests again and Memory test went from 75th to 97th percentile. The world rating is irrelevant of course but the actual clock rate went up from 2417 to 3118 in CPU-Z.

A 29% free boost!

Learn from my mistake and enable XMP profile if you paid the extra for faster memory that supports it!

Please note my system is otherwise default I do NOT overclock ever for stability reasons. XMP is a manufacturer supported settings table on the chips themselves so tested to be stable.

DISCLAIMER:If you are unfamiliar with how to enter or edit your BIOS/UEFI I'd recommend not changing anything. 

Screenshots below:

Without XMP and WITH XMP Enabled In UEFI

Great thread! Enabling XMP (or the AMD equivalent EXPO) in the BIOS is easy and should be safe. I’ll do a performance comparison in the sim with XMP on/off (and probably also hyperthreading on/off), should be interesting.

While everyone's busy discussing the 777, I'll share my results after a few hours of in-sim testing. Just note that I've got an AMD system, so: 

EXPO

• memory overclock profile (similar to Intel's XMP)
• without EXPO, my DDR-5 runs at 4800MHz, with EXPO 6000MHz (timings are also better)

SMT (simultaneous multithreading) doubles the threads per core. With SMT on, my 16-core CPU will have 32 threads. The Intel equivalent is HT (hyperthreading).

Test conditions:

• Fenix A320

• Aerosoft ENGM Oslo Gardermoen

• AIG traffic 100% with Traffic Controller

• Weather preset: //42 SimFX - Cinematic

• Time: 1900z

• Holding pattern GRM inbound 315, R, 2nm, 3000ft, 220kts

• External camera with smartcam locked to ENGM

• 5 min test runs

Results:

• Average FPS 11% higher with EXPO on (68.5 => 76.6)
• Frame time variance (correlates with smoothness) significantly better with EXPO on
• Average FPS 9% lower with SMT on
• FTV slightly worse with SMT on

I found this very interesting! My thoughts: 

1. I didn't think the performance increase would be that big with EXPO on
2. I didn't expect that performance would be that much worse with SMT on

My theory for worse performance with SMT: The total CPU temperature will probably be considerably higher with SMT on, so that there will be less thermal headroom for AMD's turbo boost clock. Also, it's doubtful that MSFS will be able to utilize 32 threads efficiently. 

TL;DR:

XMP/EXPO on and HT/SMT off in the BIOS might give a significant performance boost.

...

I've made a video of my findings which can be found in my YT channel. It's not done yet though as I have to edit it first 😉

Edited June 26, 20241 yr by Cpt_Piett

Thanks for confirming what I was thinking, @Cpt_Piett! I saw the same effects of XMP in Passmark, but I never bothered to test in any sims.

BTW, EXPO may be an AM5 thing. In AM4 motherboards, it was still called XMP... or at least in my mobo.

35 minutes ago, Cpt_Piett said:

My theory for worse performance with SMT: The total CPU temperature will probably be considerably higher with SMT on

I remember the late NickN was against using HT. This was his reasoning:

Quote

The reason you SEE logical core activity in the Windows CPU monitor window is because the physical cache is used for each logical (hyper thread) core. "logical" core means there is no 'physical' hardware core but the hardware cache in use is there, and, FSX is DUMB so a thread is spawned due to the physical cache in use, but the data is never processed and used by FSX!

That was during the Haswell days, when 6 cores were only for i7 Extreme CPUs. I'm sure LM did nothing about this for P3D, and based on your results, I guess Asobo also did nothing for MSFS.

Edited June 26, 20241 yr by Luis Hernandez

1 hour ago, Luis Hernandez said:

BTW, EXPO may be an AM5 thing. In AM4 motherboards, it was still called XMP... or at least in my mobo.

And luckily both XMP and EXPO profiles can be used on the AM5 platform.

5 hours ago, Cpt_Piett said:

My theory for worse performance with SMT: The total CPU temperature will probably be considerably higher with SMT on, so that there will be less thermal headroom for AMD's turbo boost clock. Also, it's doubtful that MSFS will be able to utilize 32 threads efficiently. 

IIRC, the game running efficiency of the 7950X3D's 3D cache collapses when all cores are enabled and running.  That is why the 7800X3D can hold its own so well with MSFS, it's 3D cache always runs at peak efficiency with its 8 cores.

It'd be interesting to run your SMT test with your 7950X3D in game mode, i.e. with only 8 cores enabled.

Edited June 27, 20241 yr by TheFamilyMan

12 hours ago, TheFamilyMan said:

IIRC, the game running efficiency of the 7950X3D's 3D cache collapses when all cores are enabled and running.  That is why the 7800X3D can hold its own so well with MSFS, it's 3D cache always runs at peak efficiency with its 8 cores.

It'd be interesting to run your SMT test with your 7950X3D in game mode, i.e. with only 8 cores enabled.

That’s an interesting thought. I might give that a try. Got a modest overclock going, focusing on the “cache cores” 1-8, so very happy with how the sim runs. Basically in sim sessions, core 9-16 are barely getting used at all. 

Not that related to this thread, but also not completely unrelated. As mentioned earlier, I got a performance (fps) boost of 11% by enabling EXPO. With EXPO + a modest CPU overclock, the overall performance boost was 17%. I'll make a video on this.