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What will I lose or gain?

timlab
Level 9

I have a Intel Core I9-11900K chip with a Z-590-e motherboard.  This board has 4 M.2 slots.  Currently, I have one M.2 in M.2-1 slot (just under the GPU).  I would like to add another M.2 to the board.  Any suggestions on what I can expect, and what will I lose/gain from this?

Thanks

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timlab
Level 9

Ty for your help in this matter.

Dan

View solution in original post

14 REPLIES 14

Silent_Scone
Super Moderator

Hello,

If not wanting to drop to 8X on the GPU you should use M.2_3 or M.2_4 both of which use Chipset lanes.

13900KS / 8000 CAS36 / ROG APEX Z790 / ROG TUF RTX 4090

Thank you for answering me so quickly.  Question:  What SATA ports will I lose if any?

Thechin
Level 8

I have the same board and cpu. The M.2_2 slot is the only other PCIe 4.0 slot M.2_3 and M.2_4 are both PCIe 3.0.

You also have to change this setting in the BIOS to turn it on though otherwise the SSD won’t be recognized.
Go to Advanced. Then to Onboard Devices Configuration.
Then change  CPU PIE Configuration Mode to:

[PCIEX16_ 1 ÷ PCIEX16 2 + M.2 2]

Turning it on shares resources though and will drop to x8 for the GPU.

When I was building my PC and installing the M.2 in the M.2-1 slot (under the GPU), I noticed there was a wire connected from the top of the cover of the M.2 to the motherboard.  The rest of the M.2 slots don't have this.  Do you have any clue what makes this one so special?

Dan

The wires will be for the LEDs under the Strix logo on the cover/heatsink.

timlab
Level 9

If I put my M.2 (1TB) into M.2(2) the speed of the GPU will go down from x16 to x8.  Am I correct on this?  Then if I put my M.2 (1TB) into M.2(3 or 4) I will lose a SATA port.  Am I correct on this?  I am using this M.2 drive for a catch-all (when I need some storage).  So if this was your system, where would you put the M.2 drive?

Thanks

Dan

Murph_9000
Level 14

M.2_1 should normally be your OS/system drive, and uses the dedicated x4 storage lanes on the CPU (11th gen only, not available on 10th gen).

M.2_2 steals GPU lanes, limiting you to x8 for the top GPU slot and x4 for the second GPU slot.

M.2_3 is via the chipset and shouldn't impact SATA ports (or anything else)

M.2_4 is via the chipset and shouldn't impact SATA ports for PCIe/NVMe drives, but does disable SATA6G_2 if you use it for a M.2 SATA drive.  M.2 SATA drives are relatively unusual these days, essentially legacy status.  The other M.2 slots do not support SATA drives, only PCIe/NVMe.

M.2_3 and M.2_4 share the chipset bandwidth with all other chipset devices.

With a single M.2 NVMe drive, it should always go in M.2_1.  This is your highest performance storage slot, and will vastly outperform any SATA drives with a good PCIe 4.0 x4 NVMe drive installed in it.

timlab
Level 9

Thank you Murph_9000 for that info.  I have one SAMSUNG 980 SSD 2TB PCIe NVMe Gen 4 Gaming M.2 which is in my M.2_1 slot.  I'm getting another drive (same type of drive only 1TB) and wondering where I should put this without losing anything esp. SATA port.  So by your above post, I should put this in the M.2_3 slot, so I don't lose anything.  But from above you state that "M.2_3 and M.2_4 share the chipset bandwidth with all other chipset devices.  Therefore, I would lose my SATA6_2 correct?

Thanks

Murph_9000
Level 14

No, the shared chipset bandwidth just means that M.2_3 and M.2_4 do not have dedicated PCIe lanes back to the CPU.  They share a single x8 connection between the chipset and CPU.  All devices connected through the chipset share that link.  You only lose SATA6G_2 if you install a legacy M.2 SATA drive in M.2_4; if you install a modern M.2 NVMe drive in the slot, you do not lose any SATA ports.  What it means is that if you have a lot of other IO going on, i.e. SATA, USB, network, etc; that competes for bandwidth with the M.2 drives in the chipset slots.  I.e. you can't run two x4 NVMe drives at full speed via the chipset while other IO is active.  It's not the same as stealing lanes for a different purpose, just a lot of different IO sharing a single pipe back to the CPU.

With two M.2 NVMe drives, your primary/boot/system drive should normally be in M.2_1.  Your secondary drive can go in either M.2_3 or M.2_4, but M.2_3 makes logical sense as the next port in the sequence (after skipping M.2_2).

Here is the Z590 block diagram from the Intel® Z590 Chipset Brief.  The x8 3.0 link between the CPU and chipset is essentially a bottleneck that limits the total IO available through the chipset.

Intel® Z590 Chipset Block DiagramIntel® Z590 Chipset Block Diagram