NVRAM is not popular to PC users but it is very familiar to Mac users. NVRAM is a type of RAM that retains data after the host device's power is turned off. ( in contrast to RAM ). NVRAM is used to store values like: brightness, volume, computer name, Find My Mac’s ID, etc… In Windows and Linux these values aren’t stored in NVRAM but on the HDD, as most PCs don’t have NVRAM. OS X utilizes NVRAM to run many services like iMessage, FaceTime, boot device, etc…
关于开机前的几秒花屏，专业说法应该是 Second Stage Boot graphics glitch ，相应的clover patch
<dict>
<key>Comment</key>
<string>Boot graphics glitch, 10.10.0/10.10.1 (1 of 2)</string>
<key>Name</key>
<string>#IOGraphicsFamily</string>
<key>Find</key>
<data>hcB0XUg=</data>
<key>Replace</key>
<data>McB0W0g=</data>
</dict>
<dict>
<key>Comment</key>
<string>Boot graphics glitch, 10.10.0/10.10.1 (2 of 2)</string>
<key>Name</key>
<string>#IOGraphicsFamily</string>
<key>Find</key>
<data>QYjE6wM=</data>
<key>Replace</key>
<data>QYjE6yM=</data>
</dict>
<dict>
<key>Comment</key>
<string>Boot graphics glitch, 10.10.2 (1 of 2)</string>
<key>Name</key>
<string>IOGraphicsFamily</string>
<key>Find</key>
<data>QYjE6xE=</data>
<key>Replace</key>
<data>QYjE6zE=</data>
</dict>
<dict>
<key>Comment</key>
<string>Boot graphics glitch, 10.10.2 (2 of 2) (seems to have no effect)</string>
<key>Name</key>
<string>IOGraphicsFamily</string>
<key>Find</key>
<data>hcB0a0g=</data>
<key>Replace</key>
<data>McB0W0g=</data>
</dict>
复制代码
针对的系统版本，代码里有 ，找到自己现在用的系统版本 ，删除IOGraphicsFamily的#号就会使该patch生效了。
note：Keep in mind the glitch never completely goes away... that patch only reduces the severity.（花屏不会彻底消失，只是减轻而已。so....）
沙发 最后的一个帖子 
