Problem with identical twin rigs

[sns26]

Almost identical rigs - one boots, one won't!

I’m an experienced Hackintosher, and have built several functioning rigs over the last ~7 years thanks to this forum. I have a problem with inconsistent (and occasionally non-existent) booting on a H77N-wifi with a Sandy Bridge cpu.

I have two rigs with same mobo (H77N-wifi, F2 BIOS) but different CPU. Both have worked beautifully in Mtn Lion but I am having trouble in Yosemite.

One rig, "Ivy,” has aIvy Bridge core I3 CPU, 3.0ghz model 3225, CPU id 306a9.
The other rig, “Sandy,” has a Sandy Bridge core I3 CPU, model 2125, CPU id 206A7.

Optimized default settings, no PCI cards, no extra USB devices, and no graphics card. I installed using a Unibeast v5.2 USB stick and the most recent installer from the App Store (10.5.5).

“Ivy” is easy. I can boot easily from the USB I create, install quickly to the HDD, and run multibeast according to the settings below. I get a 98% functional boot drive in about 20 minutes.

“Sandy” is difficult. She will not boot from my Unibeast USB installer—she hangs up after the IO-Bluetooth-whatever message. Because I know that mixed Sandy-Ivy graphics (3000-level GPU with 7-series mobo) are an issue, I used “Ivy” to create a boot disk that would work on "Ivy," then ran Multibeast on it (while still installed in "Ivy") to install the mixed-graphics patch. But that disk only occasionally will boot "Sandy." I even went back to an earlier version of Multibeast to try the same things.

The last thing I see before kernel panic on "Sandy" is: "p state stepper error 18 at step 2 in context 2 on cpu." Crash screen below.

The bizarre thing is that the disk *sometimes* boots. Any ideas? Help!

 

[sns26]

Okay, this is very interesting.

If I create the boot drive on the Ivy machine, then run multibeast with the mixed graphics patch, I CAN use it to boot the Sandy machine into safe mode with a -x flag.

What is weird is that once I boot once WITH the -x flag, I can then boot once or twice WITHOUT it. In other words, it boots just fine, no flags, 100% normal. I see four of those P-state errors flash by, but it just keeps going past them.

But after one or two normal boots, it will then hang again at the first p-state error. And then I can reset it again with a -x boot. [Update--scratch that, now I can't boot even with -x. I haven't changed anything!]

One of you knows the answer to this riddle.