I'm having issues with my rig so I decided I probably should do a full hardware sanity check. I always start with Memtest86+, the very latest version.

I discovered that my computer resets while running Memtest if I move my mouse at all. A little googling shows that this is probably because I have USB legacy support enabled.

When I disable USB legacy support, I am no longer able to boot from USB flash though. A little googling shows that this is by design.

So I have three questions.

  1. Why is booting from USB considered a legacy feature?
  2. Legacy USB support also affects the mouse and keyboard (hence the reset issue during memtest). Why is this tied to the ability to boot from flash? Why aren't they two separate options in the BIOS?
  3. How does this not mean that USB flash booting support in Memtest86+ is completely broken? Is it only some machines having this rebooting issue, or is this a common issue?

Thanks! -Kelsie


I eventually gave up and burnt a cd with memtest86+ on it. When I booted it, I discovered that Legacy USB Support has to be enabled for my keyboard to work too. In the end, the final solution I settled on was to reenable Legacy USB Support and simply unplug my mouse during the test. It seems like a pretty crappy solution, but it did the job. I'm still curious about the design behind this if anyone has any insight at all.

  • Booting from USB not not yet a legacy feature. But the method used to boot from USB is something different. – Hennes Oct 6 '12 at 20:12
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    This seeems very localized. Memtest86+ should NOT be causing the computer to reset. This indicate a serious problem with your rig. – Ramhound Oct 10 '12 at 13:45

USB legacy support was created for OS that needed additional Rom code service USB devices. NT would be an example. So would many of the power on bois tools that are available.

There could be conflicts between the bios tools and the bioses themselves regarding USB support. They are not all written by the same people but may all assume they are working without a net (pre os boot ) so the both do some low level bios control and end up conflicting.

I read the somewhere but cannot find the reference. I will look for it.


Yes, that feature behaves differently on different BIOS mfrs. I am currently looking at an older PC that, when enabled, both the keyboard and mouse do not work. This rig will only work with PS/2 HIDs (unless maybe a wireless rig which I have not tried....this belongs to a customer.)

There are however, boot settings that allow for several USB-boot options and the USB HDD boot option did work....so it may be that the BIOS needs an update... If you dare.

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