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

Back with my conclusion, i didn't do any ISR/DPC measurements but i've concluded just to stick with the drivers mobo's provided instead of using microsoft's oem driver. Thanks MBK1969

 

You realise that OEM drivers shipped with Windows are the same OEM drivers shipped with motherboard?
(May be of different versions,but OEMs are the same.)

 

Actually did not know that. I assume because everyone says "always update your drivers" that would be a good reason why to rather than use oem drivers.

 

Windows includes both MS own drivers and drivers from OEMs.

 

What's the differences between the reported PCI device type?

If I leave SR-IOV disabled, all devices in the MSI mode utility show PciExpressTreatedAsPci as the device type.

If I enable SR-IOV, some devices get PciExpressEndpoint, and others get PciExpressLegacyEndpoint. And I also get new bridge devices shown in MSI mode utility, and their type is BridgeType_PciExpressRootPort.

Specifically, my GPU (RX 580), it's HD Audio bus, AMD SATA controller, and AMD USB 3.10 controller are PciExpressLegacyEndpoint. However, my Ethernet, NVMe controller, ASMedia USB 3.1 controller, AMD USB 3.0 controller, and motherboard HD Audio controller are PciExpressEndpoint.

 

@Espionage724

https://www.mindshare.com/files/resources/MindShare_Intro_to_PCIe.pdf :
(page 11 - PCI Express Topology)

• A Root Complex connects the CPU and memory subsystem to the PCI Express fabric.
• A Hierarchy is the network or fabric of all the devices and Links associated with a root complex that are either directly connected to the root complex via its port(s) or indirectly connected via switches and bridges.
• A Hierarchy Domain is a fabric of devices and Links that are associated with one port of the root complex.
• Endpoints are devices other than root complex and switches that are requesters or completers of PCI Express transactions. They are peripheral devices such as Ethernet, USB or graphics devices. Endpoints initiate transactions as a requester or respond to transactions as a completer. Two types of endpoints exist, PCI Express endpoints and legacy endpoints.
  • Legacy Endpoints may support IO transactions, and may support locked transaction semantics as a completer but not as a requester. Interrupt-capable legacy devices may support legacy style interrupt generation using message requests but must also support MSI generation using memory write transactions. Legacy devices are not required to support 64-bit memory addressing capability.
  • PCI Express (native) Endpoints must not support IO or locked transaction semantics and must support MSI style interrupt generation.
• Multi-Function Endpoints. Like PCI devices, PCI Express devices may support up to 8 functions per endpoint with at least one function being number 0.
• PCI Express-to-PCI(-X) Bridge is a bridge between PCI Express fabric and a PCI or PCI-X hierarchy.
• A Requester is a device that originates a transaction in the PCI Express fabric. The Root complex and endpoints are examples of requester devices.
• A Completer is a device addressed or targeted by a requester. A requester reads data from a completer or writes data to a completer. The Root complex and endpoints are examples of completer devices.
• A Port is the interface between a PCI Express component and the Link, and consists of differential transmitters and receivers. An Upstream Port is a port that points in the direction of the root complex. A Downstream Port is a port that points away from the root complex. An endpoint port is therefore, by definition, always an upstream port. A root complex port(s) is a downstream port.
  
• A Switch can be thought of as consisting of two or more logical PCI-to-PCI bridges, each bridge associated with a switch port.

PS And SR-IOV is:
Single Root I/O Virtualization (SR-IOV) interface is an extension to the PCI Express (PCIe) specification. SR-IOV allows a device, such as a network adapter, to separate access to its resources among various PCIe hardware functions.
https://docs.microsoft.com/en-us/wi...ew-of-single-root-i-o-virtualization--sr-iov-

According to that linked page primary usage for SR-IOV is in Hyper-V virtualization stack.

PPS
I would enable SR-IOV in your place but you have to test whether it gains any performance or quality.

 

It came to my attention just now that Latencymon 7.00 has a flaw with the user process latencies resulting in misreporting by several factors (too high)

On a (arguably busy) system with 60-2000 interrupt to process latency under 7.20, it was 6000-20000 under 7.00

 

Great tool, use it to kick in MSI mode for my audio drivers every time I reformat.

 

I'm confused, somehow two devices appeared in my MSI Mode Utility and both don't show any information regarding IRQ etc.:
https://i.imgur.com/QEg9SYT.png

I'm using the utility for a long time now to test stuff but I've never seen this before.

The last things I did (probably not relevant):
- bcdedit /deletevalue tscsyncpolicy
- BIOS BCLK > Auto
- Installed this Audio Driver: https://www.intel.com/content/www/u...0-64-bit-for-nuc8i7be-nuc8i5be-nuc8i3be.html?

Any idea why these showed up?

I am using Windows 10 LTSC 1809 with automatic Windows Updates disabled.

 

@xShino

Because utility works with registry, and those two devices have proper registry entries (related to MSI mode), but they just do not use IRQs.
These two devices belong to PCI Express complex itself. You can ignore them.

 

root ports do use MSIX.

 

Maybe, but on rigs with different HW and OS they are reported differently.

 

So regarding the IRQPriorityUndefined is actually the same as IRQPriorityNormal... right? Or are they little different from each other?

 

It means that no interrupt priority is forced for device, hence device uses its default priority (negotiates it with OS). Different devices can have different default interrupt priorities.

 

Fully understood thank you!

Just a very small request if you don't mind me asking if it isn't time wasting for you ... any possibility that your tool get some dark mode feature ... that would save me from eye strain from white screen when opening MSI_util_v3 I just use it alot and hence this request.

Thank you again for your knowledgeable info. and sharing it!

 

Do you mean dark mode for the utility window only, not dark mode along with Windows itself?
(https://forums.guru3d.com/threads/w...terrupts-msi-tool.378044/page-21#post-5409095)

 

Yes exactly but without using custom theme in able to make it dark so yes dark mode for the utility window only would be tremendously amazing for me

 

@THEBOSS619

What is your usage pattern of this app? Several hours per each day???

Is it enough for you to change the colors (background and text) in the grid with devices?

 

Hello,

I found a very interesting tool and I see that it is widely publicized in several videos on youtube to reduce latency. I downloaded the program, but I didn't make any changes because I didn't know if it could be a problem. I ended up finding this forum and decided to ask if you could help me configure it?

My setup is sabertooth x79 with i7 4960x. Video card gtx 980 4GB and a sound blaster z sound card.

 

you're in a thread made by the person who made said tool.

the first two devices will operate in msi
the third device might no longer output audio.