Supermicro C9Z490-PGW Motherboard Review: Comet Lake with 32 CPU PCIe Lanes

System Performance

Not all motherboards are created equal. On the face of it, they should all perform the same and differ only in the functionality they provide - however, this is not the case. The obvious pointers are power consumption, POST time and latency. This can come down to the manufacturing process and prowess, so these are tested.

For Z490 we are running using Windows 10 64-bit with the 1909 update.

Power Consumption

Power consumption was tested on the system while in a single MSI GTX 1080 Gaming configuration with a wall meter connected to the power supply. This power supply has ~75% efficiency > 50W, and 90%+ efficiency at 250W, suitable for both idle and multi-GPU loading. This method of power reading allows us to compare the power management of the UEFI and the board to supply components with power under load, and includes typical PSU losses due to efficiency. These are the real-world values that consumers may expect from a typical system (minus the monitor) using this motherboard.

While this method for power measurement may not be ideal, and you feel these numbers are not representative due to the high wattage power supply being used (we use the same PSU to remain consistent over a series of reviews, and the fact that some boards on our testbed get tested with three or four high powered GPUs), the important point to take away is the relationship between the numbers. These boards are all under the same conditions, and thus the differences between them should be easy to spot.

Long Idle and OS Idle power seem a lot higher than other Z490 boards. This will be down primarily to the PLX chip, but also the 10 gigabit Ethernet on board.

Non-UEFI POST Time

Different motherboards have different POST sequences before an operating system is initialized. A lot of this is dependent on the board itself, and POST boot time is determined by the controllers on board (and the sequence of how those extras are organized). As part of our testing, we look at the POST Boot Time using a stopwatch. This is the time from pressing the ON button on the computer to when Windows starts loading. (We discount Windows loading as it is highly variable given Windows specific features.)

Despite not being a server board for Xeons, or having an IPMI, the Supermicro system has a similar POST time to those server boards. Part of this will be down to the PLX chip, but there is also consideration on CPU detection and training - a system can POST faster if it auto-assumes that the CPU and DRAM are the same as the last time it was turned on, whereas other motherboards will do a proper check every time.

DPC Latency

Deferred Procedure Call latency is a way in which Windows handles interrupt servicing. In order to wait for a processor to acknowledge the request, the system will queue all interrupt requests by priority. Critical interrupts will be handled as soon as possible, whereas lesser priority requests such as audio will be further down the line. If the audio device requires data, it will have to wait until the request is processed before the buffer is filled.

If the device drivers of higher priority components in a system are poorly implemented, this can cause delays in request scheduling and process time. This can lead to an empty audio buffer and characteristic audible pauses, pops and clicks. The DPC latency checker measures how much time is taken processing DPCs from driver invocation. The lower the value will result in better audio transfer at smaller buffer sizes. Results are measured in microseconds.

Normally anything under 250 microseconds is good, however it is clear that the other vendors are doing something that Supermicro is not.