Bear MSI Z790 Motherboard

Published 2022-12-29.

MSI MAG Z790 Tomahawk WIFI

MSI MAG Z790 TOMAHAWK WIFI LGA 1700 Intel Z790 SATA 6Gb/s ATX Motherboard

The black covers over the NVMe slots (shown as M2_1, M2_2, M2_3 & M2_4) are much larger than shown above

M.2 Connectors

The NVMe slot covers are labeled D1, D2, D3 & D4, as shown in the following image.

Top view of motherboard, showing labeled NVMe slot covers

This motherboard provides four PCIe 4.0 x4 M.2 slots for NVMe SSDs. The first of them, M.2_1, hidden under a black cover with D1 written on it, is between the video card slot and the CPU. M.2_1 gets 4 dedicated lanes from the CPU, which means it doesn't take lanes away from the PCIe slots. This slot supports large to extra large NVMe SSDs with 22110/2280/2260 formats. Once the Noctua NH-D15S air cooler is installed, access to this NVMe slot is impossible, so this NVMe device must be installed before the air cooler. I installed the system drive in this slot.

The other M.2 slots are powered by the Intel Z790 chipset. The D2 slot only supports the larger 2280/2260 formats, while D3 and D4 support 2280/2260/2242 formats. SATA_1 is unavailable when the M2_3 slot (labeled as D3) is used.

D3 & D4 M.2 Connectors

The location of the D3 & D4 M.2 covers is shown in the following photograph of the fully assembled computer.

The hold-down screws for the D3 & D4 cover are retained, fortunately, so it is relatively easy to work with.

D3 & D4 cover after removal, obverse, showing heat transfer pads with plastic coverings still on

The D3 & D4 cover acts as a large heatsink. Be sure to remove the plastic sheet over the thermal putty before inserting an NVMe chip under it.

Closeup view of D3 & D4 without the cover, showing the M.2 connector and retaining post

Before a NMVe chip can be inserted, the screw for the corresponding retaining post might have to be loosened slightly.

BIOS Update for Intel Core i7-13700K

The MSI MAG Z790 won’t work with an Intel Core i7-13700K until the BIOS is updated. Happily, MSI provides a way to update the BIOS using just the motherboard with nothing connected except a flash drive. That is, without a CPU, memory, keyboard, or video card installed. There is no need for cooling fans for this procedure if no CPU or memory is installed.

The procedure is described on page 57 of the User Manual, and in How to Flash the BIOS.

I have added my experience to the following summary of steps to flash the BIOS:

Download the latest version, AMI BIOS 7D91vH1 2022-11-21 9.35 MB. The default name of the download file was 7D91vH1.zip.
Extract the BIOS file, which for me was called E7D91IMS.H10 and was reported as 32,768 KB, even though it was only 10.9 MB. So, a 1 GB USB drive would easily accommodate this file.
Rename the BIOS file to MSI.ROM
Obtain an empty USB drive, 32 GB or smaller, formatted as FAT32. Best if you actually format the drive, to ensure no hidden files exist on it. Do not use the flash drive provided in the box because there should be no other files or folders on the USB drive. Copy MSI.ROM to the root of the USB drive.
Insert the flash drive into the USB port on the motherboard back panel labeled Flash BIOS.
Connect the power supply to CPU_PWR1 and ATX_PWR1. No need to connect CPU_PWR2.
Power on the motherboard.
Press the CMOS Reset button.
Press the Flash BIOS button once. About 5 seconds later, the LED next to the USB port will start to flash. After 15 seconds or so, the speed of the flashing light will double, while the BIOS is updated. The LED next to it should flash for 6-7 minutes. The LED will stop flashing when the process completes and the power will turn off.

On my system, the LED next to the Flash BIOS button lit up when the button was pushed, but it did not flash. I tried several USB drives, with capacities ranging from 2 GB to 32 GB, with the same result. Then I tried pushing Flash, Clear, Flash and the LED started to blink. The fans stopped, then restarted, and the LED continued to blink. After several minutes the LED stopped blinking.

USB Headers

Nomenclature for USB 3 has changed over the years, which initially caused me a lot of confusion. Christopher Harper’s article on CG Director entitled What Are USB Headers & How Do You Get More? set me straight. To summarize:

USB 3.2 Gen 1 is also known as USB 3.0
USB 3.2 Gen 2 (usually exposed with a USB-C connector) is also known as USB 3.1

USB 3.2 Gen 1 and Gen 2 Headers.<br>From “What Are USB Headers & How Do You Get More”

USB 3.2 Gen 1 and Gen 2 Headers.
From “What Are USB Headers & How Do You Get More”

MSI MAG Z790 Headers

3 of the 4 USB headers on the MSI MAG Z790 Tomahawk WIFI need cable assemblies with connectors on PCI slot covers. My old Antec case, provides the wiring assembly for 1 USB 2.0 header, which breaks out to 2 USB 2.0 connectors; this assembly routes to the front of the case.

Page 17 of the MSI MAG Z790 Tomahawk User Guide shows the following internal USB headers:

JUSB1 & JUSB2: 2 USB 2.0 Type-A connectors (From hub GL850G) — supports a total of 4 USB 2.0 ports. I already have one cable assembly for the front of the case as previously mentioned, and I will attach it to JUSB2. 1 additional cable assembly is therefore required for the JUSB1 USB 2.0 header, and it will be routed to a PCI slot cover.
JUSB3: 1 USB 3.2 Gen 1 5Gbps connector (From hub GL3523) — supports 2 USB 3.2 Gen 1 5Gbps ports. All the cable assemblies that I found were labeled as USB 3.0 compatible, not USB 3.2 Gen 1.
JUSB4: 1 USB 3.2 Gen 2 10Gbps Type-C front panel connector (From Intel Z790 chipset). Compatible cable assemblies might be labeled as USB 3.1 compatible, or USB 3.2 Gen 2, or USB-C.

JUSB1 and JUSB2 (USB 2.0 connectors).

Left: JUSB4 (USB 3.2 Gen 2 connector), right: JUSB3 (USB 3.2 Gen 1 connector).

Another view of JUSB4 and JUSB3.

PCI Slot Covers

The case has cutouts for 7 PCI slot covers. The video card uses 2 slots. 5 PCI slot cover cutouts are therefore available.

The cable for JUSB1 needs to be at least 6 cm long;<br>some extra length would be best.

The cable for JUSB1 needs to be at least 6 cm long;
some extra length would be best.

The cables for JUSB3 and JUSB4 need to be at least 33 cm long;<br>some extra length would be best.

The cables for JUSB3 and JUSB4 need to be at least 33 cm long;
some extra length would be best.

It is important that as few PCI slot covers are required as possible; thus, each PCI slot cover should have as many connectors on it as possible.

Example of a fully populated PCI slot cover.

I do not need 4 USB 2.0 connectors on a PCI slot cover. Below is a mock-up of the desired cable assembly.

It would be best if both USB 2.0 connectors were attached to the same PCI slot cover as the USB 3.2 Gen 1 connectors, as shown below.

Desired cable assembly, using only 1 PCI slot cover.

However, if the USB 3.2 Gen 1 connectors are only available together on a separate PCI slot cover, that would also work. As previously mentioned, the USB 3.2 Gen 1 cable in the above assembly should be at least 33 cm long.

USB 3.0 / 3.2 Gen 1 cable assembly.

The USB-C connector might look like this (again, the cable should be least 33 cm long):

USB-C / USB 3.2 Gen 2 cable assembly.

MSI Software

The new system came right up and I logged into Windows without any issues. I was amazed! The drivers had to be installed before the network could be accessed, so I inserted the USB drive that came with the motherboard, and double-clicked the ISO image to mount it. The MSI software and drivers installed without issue, and everything worked, even WSL 2 with systemd and graphics support. Unbelievable!