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I downgraded from Yosemite Public Beta to Mavericks by:

  1. Created bootable Mavericks USB
  2. Booted Mac to the Mavericks USB
  3. Went into Disk Utility > Selected HD and Erased HD
  4. Restored to Mavericks Time Machine Backup which was successful

However, when I boot the Mac and hold option to go to the Startup Manager screen it is still the Yosemite startup manager. Is there any way to revert to the Mavericks Startup manager? The Yosemite Startup Manager is Black background with the disk selections, and the Mavericks is light gray background with the disk selections. Has anyone else seen this?

Does it even matter?

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  • A bit late, but I always swap out my Time Machine drive if I test a beta OS, then my original Time Machine is clean, to which I can add any later document backups. Your Time Machine is now a blend of 2 backups, only thing I could think would be to restore to before your Yosemite foray, if possible, & then pick out specific docs afterwards.
    – Tetsujin
    Sep 18 '14 at 19:53
  • I've got the same problem on my 13 inch rMBP, mid 2014. I was googling a little bit and it is said that the Yosemite automatically updates efi or smc on 2013+ models, which causes the black boot screen and also startup manager having the black background. Is your Mac running OK after the downgrade? Mine is freezing terribly, especially on youtube, ebay and App Store, and it is not just the web browsing, it's also freezing quite frequently when using the finder too. Before the downgrade from Yosemite back to Mavericks I never had any problems on Mavericks. So, I just reseted the SMC, so I am re
    – user97198
    Oct 23 '14 at 11:32
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The question does not mention a model, let's assume that the Mac is a model that gained a firmware update in connection with Yosemite.

If so, then – for use with Mavericks (without Yosemite) – it may be desirable to reinstall lesser firmware.

… Erased HD …

– that would have erased an operating system without affecting firmware.

A suggestion

  1. System Information will tell what firmware is installed
  2. compare what's installed with https://web.archive.org/web/20141010090340/http://support.apple.com/kb/HT1237 (the 2014-09-23, pre-Yosemite edition of an article)
  3. compare what's installed with the current, post-Yosemite edition of the same article: EFI and SMC firmware updates for Intel-based Macs – Apple Support.

Related

Amongst Macs that can be upgraded to support OS X Recovery, can any model not accept a firmware downgrade?

Kernel Programming Guide: The Early Boot Process

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