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Re: [SOLVED] System broken after yesterday's upgrade

On Thursday, 13 April 2017 12:44:06 CEST solitone wrote:
>  I tried and reset NVRAM, a nonvolatile random-access memory that
> Macs use to store certain settings like sound volume, display resolution,
> and (I realise only now) startup disk selection.. and GRUB doesn't start
> any longer, it boots up directly into MacOS.
> After that, I also reset the System Management Controller (SMC) and at least
> now the initial bootup phase into MacOS is much quicker.
> Now I managed to restore GRUB, using the rescue mode option of my
> installation USB stick. Everything is as before: very slow keystrokes
> response in grub, integrated keyboard and mouse working after some time in
> login screen only when external usb mouse and keyboard plugged in (both of
> them!)
> I've noticed that also Apple Startup Manager suffers from the same issue
> that GRUB has: I press keys and it responds after tens of seconds! Trackpad
> is also very slow or doesn't work at all. I need to check my updates on
> Apple side..

The thing I didn't explain there is that after I reset the SMC, MacOS boot 
seemed to be quicker, however it still tooked 30 seconds or more to start the 
Startup Manager when pressing the alt button at startup. Besides, Startup 
Manager responded very slowly to keypresses, and the trackpad didn't work, or 
was really slow. This clarifies the issue wasn't a consequence of reinstalling 
GRUB, and I suspected it depended either on Apple's hardware or in some low 
level Apple software component.

I found a few posts around that described exactly the same problem I had, like 
this one:

Some people said that MacOS Siera 10.12.4 would solve that issue. So I tried 
and upgraded (I was on 10.12.3), and I can confirm it is indeed true. That 
system update must contain also a firmware update that addresses that I/O 
issue. Now everything works very well again.