USB LEGACY SUPPORT / XHCI HAND-OFF

[Slender]

legacy usb support - 1.1 / 2.0 (on - mean bios control, off - os control)
xhci hand-off - 3.0 (on - mean bios control, off - os control)

[adrian_13371]

legacy usb support - 1.1 / 2.0 (on - mean bios control, off - os control)
xhci hand-off - 3.0 (on - mean bios control, off - os control)

Isn't it the other way around? Xhci on-os control, off-bios control?
Chat gpt says so

[kyube]

We are talking about 3 different settings, which are: Legacy USB Support, XHCI Hand-Off, EHCI Hand-Off

Their status heavily depends on the following variables:
1.) Operating system you're currently on (XP, W7, W8.1, W10, W11, Linux, MacOS/Hackintosh, Android, BSD-based...)
2.) Drivers you're using for USB (stock Microsoft USB drivers, Intel/AMD-specific from W7 era or later which can be found through Fernando's USB forum thread, 3rd party vendor such as ASMedia, Renesas, Fresco Logic etc.)
3.) BIOS version you're running
4.) How application SW you're interested in optimising your OS/BIOS for interacts with changing these settings
5.) How peripheral software (Razer, Steelseries, Logitech) & mouse react to such changes
6.) Whether your peripherals are wired or wireless (USB 3.0 & wireless mice don't play well)
Source: https://www.usb.org/sites/default/files/327216.pdf
USB 3.0* Radio Frequency Interference Impact on 2.4 GHz Wireless Devices
White Paper
April 2012
Document: 327216-001


There hasn't been any total peripheral latency and/or DPC & ISR testing by analysing .ETL logs using scripts such as xperf, xtw or tools such as MXA, so the general answer is: it depends

Here are a few inserts I've found in regards to this topic from Intel engineers:




from B250M-HDV (Kaby Lake motherboard) manual




During DDR3 era hardware, where W7 was main OS for Microsoft, Intel engineers seemingly suggested
XHCI hand-off: Enabled
I pressume they've done that due to lacking native support of USB 3.0 on W7. They've also stated that it depends on BIOS manifacturers.

NOTE: This above does not apply to W10 or later, which has built-in support for XHCI hand-off, pressumably due to stock MS drivers

It should very likely be XHCI hand-off: Disabled on W10 & later, but keep in mind actual testing data would be necessary to come to a proper conclusion, so take this recommendation with a huge grain of salt.
Always consult official sources and/or people with verifiable testing data.

A few sources in this regard:
https://superuser.com/questions/1363175 ... ontrollers
https://superuser.com/questions/770198/ ... -windows-7
https://winraid.level1techs.com/t/outda ... /30871/987
https://linustechtips.com/topic/1376063 ... r-enabled/
https://www.tenforums.com/performance-m ... ost1848118
https://answers.microsoft.com/en-us/win ... 20056ae65c
https://rog-forum.asus.com/t5/z170/xhci ... d-p/535397 [disabled by default on ROG Z170 board]
https://www.oreilly.com/library/view/pc ... 01s09.html [info in regards to Legacy USB support]
https://praxistipps.chip.de/legacy-usb- ... ung_162965 [legacy USB support talk]
https://github.com/morrownr/USB-WiFi/issues/508
https://forum-en.msi.com/index.php?thre ... rt.394039/ [MSI mobo anecdote]
https://forum.asrock.com/forum_posts.as ... ot-working [CPU lanes USB ports on AMD require a different approach on Asrock for downgrading them from 3.0 to 2.0]

Previous discussions in regards to this topic:
viewtopic.php?t=13434

I would personally opt for both “XHCI Hand-Off” & “EHCI Hand-Off” set to Auto or Disabled, while keeping Legacy USB Support to Auto or Enabled because I don't own a PS/2 keyboard & like to use my USB keyboard to navigate through the BIOS & use a USB flash drive for OS installations.
There's probably more nuance to this topic, especially on the format of the USB flash drive (FAT32, exFAT, NTFS, ext2–4...), type of boot sector (MBR, GPT), CSM status (enabled/disabled) etc.
Auto would probably be the wisest choice, so that the motherboard decides what's best for the given OS of choice.
I have no basis or data to back-up my personal choice.

[Hyote]

There is another setting called XHCI Legacy Support, keep that one enabled.
Edit: keep it enabled, otherwise you won't be able to access the BIOS. I keep it disabled.