UEFI CSM / legacy performance

Are there any known performance problems of "legacy" Operating Systems (Windows 7, for example) running on UEFI with CSM?

Lately, I've seen quite a few brand-new computers by different OEMs that have pretty decent specs but are running Windows 7 on UEFI and their performance is dreadful even when freshly installed.

It may be a coincidence or seeing patterns in the sand but, if I recall correctly, it started around the time that Windows 8 and, therefore, UEFI became mainstream.

mythofechelon

Posted 2015-10-19T09:31:42.970

Reputation: 653

UEFI was available long before Windows 8. – Daniel B – 2015-10-19T09:45:02.377

The performance of those machines have absolutely NOTHING to do with them being ran in non-legacy mode. – Ramhound – 2015-10-19T10:53:24.877

@Ramhound Hence, the question. Isn't downvoting me for asking a question (the purpose of this site) a bit harsh? Also, where is your source? – mythofechelon – 2015-10-19T10:55:24.067

Answers

None that I know of, like BIOS which it replaces, UEFI is really only for booting the machine and starting up all the hardware correctly before handing control to the Operating System, so shouldn't be impacting on performance while it's running.

CSM compatibility support module provides support for older operating systems but again it's for booting the machine and hardware.

Kilisi

Posted 2015-10-19T09:31:42.970

Reputation: 506

1This answer is correct, but I want to add that the boot mode can affect the speed of the boot process, or at least the part of that process before the OS takes control. In many (but not all) cases, EFI-mode booting shaves a few seconds off the boot time. IMHO, this is a very minor factor, since few people reboot frequently enough for it to make any difference in how they spend their time. – Rod Smith – 2015-10-19T18:28:40.363