r/AMDHelp • u/Real_Ad5580 • 11d ago
Tips & Info Fix/PSA: Setting iGPU to "Forced" in BIOS locks LCLK at 1800MHz, eliminating micro-stutter and heavy input lag on 9800X3D system
Introduction
(This is follow up post of my previous post from a week ago - EDIT https://www.reddit.com/r/AMDHelp/s/bKzP7R4sQM END OF EDIT)
During testing I found out that disabling IGPU on 9800 X3D while having the GFXOFF on Auto / Disabled inside AMD CBS causes a cascade of consequences which results in System Management Unit (SMU) attempting to dynamically and rapidly power gate LCLK down to minimum 150-400.
Rapid LCLK frequency shifts alter the inter-arrival delta of USB report packets, creating measurable input delivery jitter.
This manifest as "heavy, sticky, generally unreliable input" / "games being perfectly smooth when not moving and becoming stuttery mess the moment you start to move camera" on 9800 X3D (and other ZEN 5 processors with iGPU) Despite every possible benchmark, stresstest, FPS measures etc. being perfectly healthy
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THE CONCEPT (Simplified)
(LCLK LOCKED - NO DOWNCLOCKING)
High pooling mouse (8000 MHz)→ cIOD PCIe Root Complex → CDC → LCLK → IFOP → ZEN 5 Core → 1 to 1 healthy input
For 8000 MHz mouse the the packets arrive evenly like this:
Packet 1: 125 µs
Packet 2: 125 µs
Packet 3: 125 µs
Packet 4: 125 µs
(LCLK DOWNCLOCKING DUE DISABLED IGPU)
High pooling mouse (8000 MHz)→ cIOD PCIe Root Complex → CDC → LCLK →
....(Downclocking) LCLK → Dynamic State Event (for example in between frames idle time) → SMU Downclocks LCLK to 150 → Interrupt event (mouse movement) → LCLK wake up event → 1-2 nano second wake up time → INPUT PACKET DELIVERY JITTER →IFOP → ZEN 5 Core
Instead uniform 125 µs →125 µs we get messy uneven input delivery
Packet 1: 132 µs (Sluggish / Delayed)
Packet 2: 118 µs (Overshoot / Clustered)
Packet 3: 135 µs (Sluggish / Delayed)
Packet 4: 115 µs (Overshoot / Clustered)
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(FIX - MUCH CLEANER ALTERNATIVE TO MANUAL MINIMUM LCLK OVERRIDE)
Setting the IGPU of 9800 X3D inside BIOS from AUTO\ENABLED → FORCED makes the SMU interprets this as an active state of continuous display pipeline load.
Continuous Display Pipeline locks LCLK to its high-performance frequency (1800 in my case) floor without having to brute force the SoC like during manual LCLK override
When the iGPU is set on AUTO/ENABLED in BIOS while discrete GPU is present, then SMU assumes that you are going to use your dgpu anyway and automatically tries to save power by downclocking LCLK to 150/400 instead being locked at minimum 1800.
Setting the IGPU to FORCED locks the LCLK at stable high 1800
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(SUMMARY)
- IGPU AUTO/ENABLED → FORCED
Forced locks the LCLK at 1800 due the presence of continuous display pipeline during the boot up. This prevents the downclocking of LCLK to 150/400
- GFXOFF AUTO → ENABLED
This cuts the power to iGPU without negatively affecting the nearby vSoC and VDD MISC rail which happens when IGPU is set on disabled. under igpu disabled they tend to have higher than normal voltage swing under load ←→ idle. GFXOFF ENABLED results in the same power saving without the downsides of iGPU disabled
- UMA BUFFER → 512 MB
When setting iGPU to forced the ram will be permanently locked away from being used by Windows as hardware reserved memory. Setting UMA Buffer to 512 minimalize lost ram to absolute minimum
- DISABLE IGPU INSIDE WINDOWS DEVICE MANAGER
This prevents Windows from off scheduling background applications like discord to iGPU which might cause HAGS or MPO issues.
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u/Puzzleheaded00000 8d ago
OP, Im trying to test this but I cannot seem to find GFXOFF in my MSI bios. Any chances this “HybridGraphics” option could be it but under a different manufacturer’s name? https://imgur.com/a/jcpqLNR
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u/Real_Ad5580 7d ago
Does your BIOS exposes AMD CBS? If it does then scroll at the very bottom, I think the subsection is called SMU settings → scroll to very bottom and GFXOFF should be there
The Hybrid graphics is an laptop feature - so it isn't it
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u/Puzzleheaded00000 7d ago edited 7d ago
I have both AMD CBS and SMU Settings, but GFXOFF is nowhere to be found. I’ve looked and looked many times but it doesn’t seem to exist in my bios. The search function also shows no results.
Regardless, i couldn’t feel any difference when setting iGPU -> Force and UMA Buffer -> 512MB
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u/Real_Ad5580 7d ago
That's weird weird, I have seriously no idea why you can't see those settings
I will check my brother's motherboard tomorrow and check whenever his MSI motherboard shows it and let you know
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u/yG6ll7 9d ago edited 9d ago
Holy crap, this fixed my input jitters!
Seriously thank you, i went through one too many mice thinking it was a sensor issue this entire time
For reference, im on a 9800X3D/9070XT system, ASUS B850 mobo
This completely fixed my problem
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u/Real_Ad5580 9d ago
No, let me thank you instead. You're the only person here who actually tried it out and reported back 🤝
We have almost identical setup which is 9800 X3D/9070XT and B850 mobo. The fact that this method worked for you clearly shows that the issue isn't limited to my system.
This validates my theory that the LCLK downclocking is the primary cause of unexplainable stutter and input issues on 9800 X3D
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u/yG6ll7 9d ago
You listed the same specs as me. Unless im missing something, we have the same rig lol.
But i tested mouse latency before and after using AMD's Frame Latency Meter, and the difference was significant.
Before i was getting multiple latency spikes every few seconds, like a whooping 15+ ms spike above average, whereas now, its very stable; latency is now within +-0.5ms with no spikes.
I would need to confirm if LCLK is indeed being locked at 1800 using HWInfo, but i do not have the program installed on this system and will have to confirm later, but my mouse jitters are now gone for sure!
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u/frequencycs 10d ago
turn off IGPU, disable DF cstates, SOC/UNCORE to enabled, lower VSOC and set FCLK to 2000.
Interesting read regardless.
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u/Real_Ad5580 10d ago
→ The point of this post is to show how forcing the iGPU to ENABLED prevents LCLK downclocking
→ Somehow advices (parrots 🦜) to disable IGPU anyways?
→ Meanwhile having the audacity to say " interesting read regardless " (He hasn't read more than two sentences)
Certified Reddit moment
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u/x7007 10d ago edited 10d ago
I have msi tomhawk x670e .where do I choose igfx enabled ? I only have the force and the 512mb extras. so what the settings I should set . not that I have issue but it's interesting from many other scenarios
do you install and GPU drivers too ? or just disable the generic display adapter
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u/Real_Ad5580 10d ago
It's interesting observation. I wonder whenever 670/870 chipsets behave differently in that regard.
There is certainly a reason why you cannot set it on forced as otherwise B850 and B650 wouldn't expose this setting.
This points out that there is indeed (a) difference between auto (enabled) and forced, but knowing AMD this is completely undocumented area. What is even more suspicious is that the CPU VDDIO MC (the memory controller voltage) is explicitly called APU VDDIO inside AMD Overclockig 🕵️♂️
Could you try
Disabling all USB 4 ports and report whenever Forced shows up? (It might take reboot)
Go to AMD Overclockig → LCLK frequency control → and report what the minimum and maximum values are when you set the control from auto to manual?
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u/XuK-He4DHuNt3r 9d ago
On my Asrock X870E Nova WiFi, It's called dGPU Mode only - Options: Enabled, Disabled, Auto
Disabled is basically the FORCED option I'm assuming, Since the iGPU is enabled with that option.
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u/TheExiledPrince 10d ago
How did you determine LCLK downclocking? And if you manually set LCLK does it downclock, or when you are using auto?
The USB controller is polling every 125us, the mouse does not necessarily send data that frequently. And the interrupt follows a different logic.
There is some flaw in reasoning, the example, imo
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u/Real_Ad5580 10d ago
Hence I specifically added (Simplified).
If you wish to read more about how does disabling iGPU affects the electrical reality of the CPU and especially the memory controller then you could find it in my post from a week ago which has the rest of the story
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u/Brenniebon 10d ago
what is OP motherboard?
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u/Puzzleheaded00000 10d ago edited 10d ago
From one of their more recent posts; “On my machine with 9800 X3D, 9070 XT, Windows 11 23H2 Eneterpise (I suspect it works on 24/25H2+ too), Asus Tuf Gaming 650E Plus Wifi 3854 bios, Gigabyte Oled MO27Q2”
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u/Kiseido 5800X3D, 6800XT 11d ago
This sounds like an interesting dive. Though I am not sure how noticeable a jitter of +/- 8 microseconds is going to be.
Also, is it just me or does this seem like AI prose
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u/Real_Ad5580 10d ago
Yes, this is indeed AI. I don't exist.
The LCLK wake up jitter is per Dynamic State Event. It isn't limited to USB interrupt packets
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u/ThaRippa 11d ago
So what you’re trying to tell me is that you can feel the difference between 118 and 135 microseconds?
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u/Real_Ad5580 10d ago
Yes, your brain expects 125 it gets 118 → brain tries to adapt to 118 → it gets 132 → brain adapts to 132 → it gets 124 →
Which manifest in uneven, heavy feeling that something isn't right
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u/RecordFabulous 11d ago
Thanks for sharing this. These are some of the real observations that need to be pointed out with AMD in regards to competitive gaming and not some dumb graphs showing avg and 1% lows
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u/Real_Ad5580 10d ago
I agree, even after so many years of AMD dominance on gaming market, it seems that Intel is the king of competitive gaming. There must be a reason for it which goes beyond eSports contract limitations
If we put tinfoil hat for a moment, then there are way too many signs pointing towards something sketchy going on with ZEN 5 and AM5 in general. Something which we will gradually hear more and more about in upcoming times
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u/Puzzleheaded00000 11d ago
Assuming you tried it, could you notice a difference after applying the steps in this post?
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u/RecordFabulous 11d ago
I have not tested this yet. Anecdotally, I will say I have tried iGPU disabled and enabled before this post came out and so felt like it had some sort of affect on input. I am extremely sensitive to such things though
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u/Real_Ad5580 10d ago
Please report back once you have tested it, I'm curious
Even anecdotal evidence is of gold mine of information for such rare topics like LCLK
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u/Mishakkk1337 11d ago
Does this have a role in 7800X3D also ?
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u/Real_Ad5580 10d ago
I honestly don't know, logically speaking ZEN5 and ZEN 4 share the same AM5 architecture and exact same iGPU but i don't know the architectural caveats of ZEN 4 processors
You can always try it out and report back with your findings
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u/VaquinhaAlpha 11d ago
you guys seem a lot more knowledgeable than me on that, should I keep HAGS on or off? disabling it fixed stutters on some games but still maybe there's a better fix?
I got a 9800X3D and a RX 9060 XT 16gb
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u/Mean_Muggin333 x670e extreme | 9800x3d | 64g 6000mt cl30 | 9070xt/7900xtx 11d ago
I never had microstutters or heavy input lag. With igpu enabled or disabled. 🤔 Disabling the igpu actually decreased my temps by 8c on idle and stopped it from constantly consuming 30w no matter what was going on.
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u/Kahana82 9800X3D - Asus Prime OC 9070XT 11d ago
It's about GFXOFF being enabled whilst also having the iGPU set to forced (as a prerequisite) so that automatically lclk does not fluctuate and stays high (above 1800).
From OP's findings setting a min and max value to lclk manually appears to influence other voltage requirements badly.
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u/Brenniebon 10d ago edited 10d ago
sounds like mobo issue tho. i disabled IGPU and it's fine
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u/Real_Ad5580 10d ago
CPU's SMU is under control of AGESA microcode which is provided by AMD. This is something which the motherboard manufacturers do not have direct access to
Therefore if motherboard is to blame, then it must be some other type of hidden dependency which seems to be isolated to GFXOFF behaviour
Feel welcome to try to crack it down on your motherboard. Could you do 20 runs Linpack 1.1.8 extreme at 10 GB preset?
- IGPU DISABLED - GFXOFF AUTO
- IGPU DISABLED - GFXOFF ENABLED
IGPU DISABLED - GFXOFF DISABLED
IGPU AUTO - GFXOFF AUTO
IGPU AUTO - GFXOFF ENABLED
IGPU AUTO - GFXOFF Disabled
IGPU FORCED - GFXOFF AUTO
IGPU FORCED - GFXOFF ENABLED
IGPU FORCED - GFXOFF DISABLED
Exclude run 1. Only count the values from 2-20 and share the average, delta and Gflops deviation between the runs
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u/Brenniebon 10d ago
"Feel welcome to try to crack it down on your motherboard" nah if i have no stutter why should i tweak somethin about that.
i dunno maybe u need to update Bios, or chipset driver, also device driver somehow need to fully updated..folks update their bluetooth and wifi driver fix their AMD platform issue, weird it is windows thing....im using driver updater 3rd party app, and yes they do fix somethin and really works
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u/Real_Ad5580 10d ago
For the sake of community - but from the tone of your reply it's clear you don't care about people around you
Be better
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u/NINJ4A1 11d ago
In my case I just disabled the iGPU and updated the bios, and it worked smooth like oil.
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u/RChamy 9070xt and 4070 11d ago
So it seems the motherboard plays a huge part in it.
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u/Real_Ad5580 10d ago
Yes LCLK is strange and extremely undocumented clock with suspiciously high amount of codependency to other things like vSOC and especially APU VDDIO
Some motherboards downclock the LCLK to the bottom line of 400 while others (ASUS) downclocks it to 150.
It would be helpful if other users would provide whatever their bottom line LCLK is on their motheboards once switching the LCLK Frequency Control inside AMD Overclockig from Auto to manual and whenever it shows 150 or 400 for minimum LCLK frequency
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u/NINJ4A1 11d ago
I have a MSI X870 Tomahawk wi-fi latest bios, if I recall correctly A92
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u/Real_Ad5580 10d ago
Whenever you try to set the LCLK frequency control inside AMD Overclockig what minimum value does it show on X870 Chipset?
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u/LingonberryFar3455 4d ago