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AM4 - M.2 Slot Question

Hi P
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Go to solution Solved by Jurrunio,
11 minutes ago, Hi P said:

1.- Most AM4 mobos only support NVMe 3.0 x4 on the M.2 slot that uses the CPU PCIe lanes, never available on the M.2 slot that uses the chipset, why is that?

 

because chipset M.2 slots share bandwidth to the CPU with other stuff on the chipset, say ethernet, USB etc. There's no spare bandwidth for a PCIe 3.0 x4.

 

11 minutes ago, Hi P said:

 

2.- What would be the difference between placing a SATA SSD on the M.2 slot from the chipset vs the M.2 slot from the CPU?

A little bit of improvement in latency (expressed in numbers) in theory since the connection is more 'direct', but the difference is too small to even measure.

 

11 minutes ago, Hi P said:

 

3.- Can you boot the OS from the chipset M.2 slot? or only from the CPU M.2 slot?

Both of your choice.

 

4 minutes ago, Electronics Wizardy said:

1. The chipset has pcie2 lanes where the cpu has pcie3 lanes

https://rog.asus.com/articles/technologies/your-guide-to-the-ryzen-am4-platform-and-its-x370-b350-and-a320-chipsets/

 

chipset also gets pcie3

I'm just taking this mobo as an example:

Asus ROG x470-F

 

Specifications --> Storage

 

1.- Most AM4 mobos only support NVMe 3.0 x4 on the M.2 slot that uses the CPU PCIe lanes, never available on the M.2 slot that uses the chipset, why is that?

 

2.- What would be the difference between placing a SATA SSD on the M.2 slot from the chipset vs the M.2 slot from the CPU?

 

3.- Can you boot the OS from the chipset M.2 slot? or only from the CPU M.2 slot?

 

Thank you

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11 minutes ago, Hi P said:

1.- Most AM4 mobos only support NVMe 3.0 x4 on the M.2 slot that uses the CPU PCIe lanes, never available on the M.2 slot that uses the chipset, why is that?

 

because chipset M.2 slots share bandwidth to the CPU with other stuff on the chipset, say ethernet, USB etc. There's no spare bandwidth for a PCIe 3.0 x4.

 

11 minutes ago, Hi P said:

 

2.- What would be the difference between placing a SATA SSD on the M.2 slot from the chipset vs the M.2 slot from the CPU?

A little bit of improvement in latency (expressed in numbers) in theory since the connection is more 'direct', but the difference is too small to even measure.

 

11 minutes ago, Hi P said:

 

3.- Can you boot the OS from the chipset M.2 slot? or only from the CPU M.2 slot?

Both of your choice.

 

4 minutes ago, Electronics Wizardy said:

1. The chipset has pcie2 lanes where the cpu has pcie3 lanes

https://rog.asus.com/articles/technologies/your-guide-to-the-ryzen-am4-platform-and-its-x370-b350-and-a320-chipsets/

 

chipset also gets pcie3

CPU: i7-2600K 4751MHz 1.44V (software) --> 1.47V at the back of the socket Motherboard: Asrock Z77 Extreme4 (BCLK: 103.3MHz) CPU Cooler: Noctua NH-D15 RAM: Adata XPG 2x8GB DDR3 (XMP: 2133MHz 10-11-11-30 CR2, custom: 2203MHz 10-11-10-26 CR1 tRFC:230 tREFI:14000) GPU: Asus GTX 1070 Dual (Super Jetstream vbios, +70(2025-2088MHz)/+400(8.8Gbps)) SSD: Samsung 840 Pro 256GB (main boot drive), Transcend SSD370 128GB PSU: Seasonic X-660 80+ Gold Case: Antec P110 Silent, 5 intakes 1 exhaust Monitor: AOC G2460PF 1080p 144Hz (150Hz max w/ DP, 121Hz max w/ HDMI) TN panel Keyboard: Logitech G610 Orion (Cherry MX Blue) with SteelSeries Apex M260 keycaps Mouse: BenQ Zowie FK1

 

Model: HP Omen 17 17-an110ca CPU: i7-8750H (0.125V core & cache, 50mV SA undervolt) GPU: GTX 1060 6GB Mobile (+80/+450, 1650MHz~1750MHz 0.78V~0.85V) RAM: 8+8GB DDR4-2400 18-17-17-39 2T Storage: 1TB HP EX920 PCIe x4 M.2 SSD + 1TB Seagate 7200RPM 2.5" HDD (ST1000LM049-2GH172), 128GB Toshiba PCIe x2 M.2 SSD (KBG30ZMV128G) gone cooking externally Monitor: 1080p 126Hz IPS G-sync

 

Desktop benching:

Cinebench R15 Single thread:168 Multi-thread: 833 

SuperPi (v1.5 from Techpowerup, PI value output) 16K: 0.100s 1M: 8.255s 32M: 7m 45.93s

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Just now, Jurrunio said:

because chipset M.2 slots share bandwidth to the CPU with other stuff on the chipset, say ethernet, USB etc. There's no spare bandwidth for a PCIe 3.0 x4.

 

Intel does that and it works fine. Most of the time most devices don't need anywhere close to the full bandwidth of the chipset to cpu link, so letting a single device fill it when needed is good.

 

1 minute ago, Jurrunio said:

Huh?

 

pcie 3 from cpu, pcie2 from chipset

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