Windows: Line-Based vs. Message Signaled-Based Interrupts. MSI tool.

@maxdigital

Also you can investigate USB ports - https://forums.guru3d.com/threads/mouse-guide.335510/page-14#post-5918816 - and test whether mouse show better results on ports without companions. I am curious.

 

Hello!
Since there're 80 pages in this thread and I've read only 32 atm lol and haven't stumbled on a solution yet, I was wondering if there's any for SMBus not getting into MSI mode.
Mine is
Intel(R) 100 Series/C230 Series Chipset Family SMBus - A123
Tried updating it from MS catalog to the latest (I assume) ver 10.1.1.38 of 03.10.2016 so far, but it still in Line-based mode.
There was no Interrupt Management\MessageSignaledInterruptProperties sections in the registry entry in the first place, so I thought maybe those aren't enough for it to work, cuz in other entries there were also such sections as Affinity Policy, Routing Info and few others, but thing is I don't really know what to change\add there or if it'll even work in the end.
Say AP - Temporal I guess should be the same as others like Qword ff for example.
I haven't messed with it yet, just wanted to make sure if it's even doable or this particular SMBus thing doesn't support MSI mode?
As of MSI utillity v3 at the first page I see that it's just doesn't support that mode, so there's no need to mess around in reg entries, am I correct?
Thanks for the thread! It's very interesting!


Edit:
What will changing interrupt priority setting affect?
Mine says that only standart controller Sata Ahci has it at High. What will happen if all\some of them would also be high? Thanks!

 

If utility reports that device does not support MSI mode then there is no need to do anything.
Utility itself messes with registry (when user either checks/unchecks MSI mode or changes the limit value) freeing user from registry manipulation.

 

We do not know. It is considered that it is bad idea to switch interrupt priorities to high for all devices.

 

If everything is a high priority, nothing is a priority.

 

Look like it has something to do with geting priority for some devices/drivers to "grab" IRQ before the others. I'll try to explain my recent experience with this...

Few weeks ago decided to move one older gaming rig from Win8.1 Pro 64bit ti Win10 Pro 64bit 21H1. Installed OS, drivers, programs... Like I always do fired up mbk1969's MSI Utility V3 to swich some devices to MSI mode and one thing caught my eye:

Intel(R) 5 Series/3400 SATA AHCI Controller

and

Intel(R) s Series/3400 Chipset Family USB Enhanced Host Controller - 3B34

...both were sharing the same IRQ 23.

Not sure what were exact IRQ numbers for these were back on Win8.1 but I'm 100% sure they were not sharing the same IRQ. Intel(R) 5 Series/3400 SATA AHCI Controller "could be" switched to MSI mode (at least MSI Utility V3 reports it's possible) but due to modded motherboard BIOS and modded Intel IRST AHCI drivers for Intel(R) 5 Series/3400 SATA AHCI Controller to work in MSI mode is out of the question: BSOD while loading Windows, nothing can be done to prevent BSOD, honestly it doesn't bother me because using IRQ mentioned controller works perfectly fine.

Back on the Win10 and situation with shared IRQ... Hmmmm... what if I switch priority to High for Intel(R) 5 Series/3400 SATA AHCI Controller?

MSI Utility V3 -> Intel(R) 5 Series/3400 SATA AHCI Controller ...priority set to: High ...restart Windows... and guess what: Intel(R) 5 Series/3400 SATA AHCI Controller ...moved from IRQ 23 to 21, while Intel(R) s Series/3400 Chipset Family USB Enhanced Host Controller - 3B34 ...has stayed ar IRQ 23. I'm perfectly fine with that

I've been using MSI Utility for years, almost sure never had situation like this before, guess it's always nice to learn something new once in a while.

edit
While drinking my morning coffe those leftover healty brain cells are starting to wake up lol. Think I've did a screenshot of MSI Utility V3 earlier on same PC I was talking above, some few months ago, screenshot used just to remind me what was the IRQ & MSI "arrangement" on Win8.1. I'll try to find that screenshot later this day and post it here together with MSI Ulility V3 screenshot now on Win10.

 

Yes, seems like MSI mode is not related to this.
Tested it a few days with MSI mode disabled, but it still occurred.

That brings me back to my first assumption that this is somewhat voltage related.
I noticed that the ASrock boards come with a default load line calibration of 3. (Ranging from 1-5)
My ASUS board has the same level range, but the levels are inverted.
Level 2-3 comes close to the ASrock level 3 one. (by looked at the screenshots/videos from reviewers.)

After changing the load line to level 3, the issue didn't appeared again.

 

I'm an idiot. Somehow I misread the device manager IRQ list. It's the Realtek NIC that's in MSI mode. Both "HD Audio" entries in there (one is the Realtek one, the other is the DisplayPort audio of my monitor) are in legacy IRQ mode.

Oops.

 

Today I was reading DDK pages related to interrupts, and I think I fully understand the interrupt priority setting introduced here - https://forums.guru3d.com/threads/w...terrupts-msi-tool.378044/page-40#post-5623597

Spoiler

We read in https://docs.microsoft.com/en-us/windows-hardware/drivers/kernel/writing-an-isr :

and https://docs.microsoft.com/en-us/windows-hardware/drivers/kernel/synchronizing-access-to-device-data :

So when we set interrupt priority of device to high we set two effects on ISR stage of interrupt handling:
- ISR of higher interrupt priority is not interrupted by ISRs of interrupts with lower priorities;
- ISR of higher interrupt priority interrupts all ISRs of interrupts with lower priorities.

But according to DDK pages device driver can fail to work at higher IRQL level because many kernel device drivers routines are not accessible from higher IRQL levels.

Initially I was confused because DPC stage of interrupt handling has its own priority in effect:
https://docs.microsoft.com/en-us/windows-hardware/drivers/kernel/organization-of-dpc-queues

and https://docs.microsoft.com/en-us/windows-hardware/drivers/ddi/ntddk/nf-ntddk-kesetimportancedpc :

 

Hi there,

i have a quick question, how can i reset the settings i made?
is there a way to see what was selected before i did change the settings with MSI tool?

Thank you

 

Of course, you can find active drivers for any device and see default values in corresponding inf-files.

 

ohh, thats good i did not know that...

Thank you mbk1969 !!!!!

 

I have 2070 Super and I disabled HAGS because I see no difference and there were reports of unstability.

 

SMBUS is legacy 2 Wire bus, it doesn't support MSI.
It's also a Interrupt Blocker, so motherboards with excessive SMBUS connected RGB crap and poor implementations of digital vrm controllers on the smbus are prime offenders for system stutter.

https://en.wikipedia.org/wiki/System_Management_Bus

 

How many games have you tested?

Use both since both can have various impact.

PS And they do not relate to each other.

 

What registry key does max limit correlate to and what does it mean? Just performed several searches and didnt find anything, no i didnt read the whole thread im doing that with several tweaks right now studying bios modules............. This procreating forum

 

Values in this column do not relate to registry keys. They are requested with Win API function SetupDiGetDevicePropertyW with PropertyKey = DEVPKEY_PciDevice_InterruptMessageMaximum.
Where DEVPKEY_PciDevice_InterruptMessageMaximum is : This property describes the number of message interrupts a device supports in hardware. This property is only valid if the device supports message interrupts.

 

Is there anyway to change it or do you think its limited in drivers or is it truly hardware limited? also how come the gpus dont list msix isnt it superior? you would think the gpus would have much higher limits than other devices but your program only lists 1 is that 1 per second? Finally figured out storage drivers and put 2048 on my ssd and yeah wow its a lot faster now latency wise. Potentially significant performance editing these values but hard to tell what its really doing.................

I just started putting 2048 on all the limits of everything where i think it might matter the gpus the root ports. Im thinking this is a significant tweak I got no bench proof but in division 2 its really cleaning the engine up its just flawless like its opening up the pcie lane latency and everything is just ultra temporal granularity............

 

I think this max limit value comes from hardware/firmware itself.

MSI-X is beneficial for server grade/side hardware - network cards, storage controllers. Consumer GPUs are not in that category.

 

Yeah but I would think that gpus would be able to do more than 1 interrupt per whatever if an ssd can do 2048. Also maybe there are inf mods to change that limit which also might give lower latency or better performance...... is there a way to test how many interrupts actually hit the device or measure or bench or test these things? We can set these values but how do we test the results? Trying to see if i can notice a difference overriding or putting higher limits in registry hard to tell tho my system is so fast and tweaked now..............