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Asus Maximus VIII Gene + i7-6700K Skylake


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This topic is to gather all information about "still waiting for root device" in one place.


Few days ago I wrote about running El Capitan on the Skylake rig




I passed all information to Pike R. Alpha, so hope he and others find the solution for everybody:

The most intresting thing is some bios option called "IOAPIC 24-119 Entries" which is enabled by default. 





You have to disable it to forget about "still waiting for root device" :-)


Why this option is intresting ? it and the other 3 options are not avaible in the newest bios version. I've allready checked all versions and it is avaible in: 0701, 0801, 0902. The newest version 0907 is missing it:



Dumping ACPI gives nothing - the tables look the same with and without that option enable. If someone want to look at it, here it is:
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Let me chime in with some background info.


iStigPL and I have been working together before, on pre-released hardware, and he contacted me with data and the vital parts like those screenshots.


The Gigabyte board that I used to setup my first Skylake system, with the Intel i5-6500 processor, before product launch, also had the same BIOS setting. It also vanished in later BIOS updated.


Then came a couple of new Gigabyte motherboards and I tried to setup a new Skylake system. This time with the i7-6700 and low and behold. It no longer worked. At first I had no idea what it was that I did. Then his (iStigPL) PM came in and I had a sort of a flash back. It hit me in the face. First we compared the ACPI tables but soon figured out that this was not part of a solution. They are basically the same.


Luckily, I immediately knew what the setting was referring to, since I had to look it up in the datasheet when I found it in my BIOS. Had no clue what it was. And if it wasn't for your (iStigPL) find, then I would still be searching for what I was missing.


Then came the e-mail from Tony offering help with testing, while you were asleep, so I e-mailed him a compiled copy of RevoBoot and told him what I was looking for. Basically the same kind of code that we were using, but this time these two lines were vital:

*(uint32_t*)(apic_base) = 0;
printf("APIC ID: 0x%x\n", *(uint32_t*)(apic_base + 0x10));

*(uint32_t*)(apic_base) = 1;
printf("Version: 0x%x\n", *(uint32_t*)(apic_base + 0x10));
The version info (second line) gave me 0x770020 on my Skylake setup but 0x170020 on my Haswell setup. What Tony did with my test version of RevoBoot was basically confirming what I PM'ed you already. In short. The new BIOS/older BIOS with the setting enabled use 0x77020 and 0x170020 when that setting is disabled.


Let me try to explain what it does. The 0x77 (hex for 119) here basically tells the OS that all Redirection Tables Entries (see the Advanced Programmable Interrupt (APIC) chapter in the Intel datasheet/page 1132 and up) are used, whereas 0x17 (hex for 23) only uses a subset of the RTE tables.


Before this iStigPL and I have been dumping other registers, but we concluded that it was garbage, and changing it did not fix the boot problems.

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Got it working on my MSI Z170A PCMate by using amibcp to edit the default value of the setting in my BIOS.


Note: earlier on, I was having trouble getting the program to save. This was fixed by updating to the newest version of the app: 5.1.something.


The OS X installer hasn't booted yet as of this post, but it got past "Still Waiting for Root Device" and is generally moving much, MUCH faster.


Edit: And the installer booted! :DDDD Thank you so much to everyone who worked on figuring this out.

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I just tried all the old BIOS versions for my Asus Z170M Plus. None of them have this setting, thus my first Hackintosh will not come to life tonight  :)

I suppose that a bootloader software fix is probably possible now the cause for the problem is known?


You can use amibcp like I did to change the setting's default value. It was pretty easy, and I'd be happy to help walk you through it if necessary. This is, of course, assuming that you're okay with the inherent (if pretty minor) risk of flashing a slightly modified BIOS.


Edit: Nevermind, there's a better solution now: http://www.insanelymac.com/forum/topic/308707-fresh-install-from-usb-installer-el-capitan-10111-beta-build-15b38b-on-skylake-i7-6700-gigabyte-z170-hd3/?p=2185480

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