AMD Motherboards - B450m steel legend BIOS v3.20

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B450m steel legend BIOS v3.20 - PCIe lanes issue

Printed From: ASRock.com
Category: Technical Support
Forum Name: AMD Motherboards
Forum Description: Question about ASRock AMD motherboards
URL: https://forum.asrock.com/forum_posts.asp?TID=14912
Printed Date: 25 Apr 2026 at 1:12am
Software Version: Web Wiz Forums 12.04 - http://www.webwizforums.com

Topic: B450m steel legend BIOS v3.20 - PCIe lanes issue

Posted By: Tiro82
Subject: B450m steel legend BIOS v3.20 - PCIe lanes issue
Date Posted: 11 Jul 2020 at 6:43am

Hi - apparently the latest v3.20 BIOS breaks M.2 NVME PCIe lane allocation.
Smasung Magician and HWinfo both show PCIe gen 3 x2

Tried manually forcing M.2 to gen 3 in BIOS, no effect

Downgrading to BIOS v2.90 fixes the issue. Drive returns to gen 3 x4 and improves drive performance.

B450m Steel Legend
Ryzen 5 3600
Samsung 970 EVO plus

Replies:

Posted By: sebastianer
Date Posted: 25 Jul 2020 at 10:53pm

I'm having the same issue in my B450 ITX (+3700X)

Sequential benchmarks write speed went down from 1600-1800MB/s to 700-900MB/s. Sometimes 20MB/s and PC gets stuck when running the sequential benchmark

This started happening after upgrading to AGESA 1.0.0.6 BIOS

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MB: ASRock B450 ITX (P3.70)
CPU: Ryzen 7 3700X
RAM: Ballistix BLS2K8G4D32AESTK
SSD: Crucial P1 500 NVME
GPU: Gigabyte G1 GTX1080
PSU: Enermax ERX530AWT --> Corsair RM650x (CP-9020178)

Posted By: Tiro82
Date Posted: 25 Jul 2020 at 11:07pm

opened a support ticket and got an updated bios that fixed the issue

Posted By: sebastianer
Date Posted: 27 Jul 2020 at 10:23pm

Really? I'll do the same. Thanks!

-------------
MB: ASRock B450 ITX (P3.70)
CPU: Ryzen 7 3700X
RAM: Ballistix BLS2K8G4D32AESTK
SSD: Crucial P1 500 NVME
GPU: Gigabyte G1 GTX1080
PSU: Enermax ERX530AWT --> Corsair RM650x (CP-9020178)