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Author Topic: Nvidia GTX 770M - iMac on Sierra OS - Issue to reset kextcache prelinked kernel  (Read 1972 times)
DrChau
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« on: February 28, 2018, 02:15:26 PM »

Hello people of the internets and Netkas forums,

I've been going through some issues on my iMac recently where I can't really get past the initial boot for my iMac since recent OS updates. I haven't really updated to HighSierra yet because of skepticism and understanding of security changes done on the OS that would not allow me to enter my hardware ID for my non-EFI not-Apple-approved MXM card.

It kind of sucks because I can't restart my machine in the hopes it would boot back up again as each time it has failed me. Every time I would need to restart I would need to get the help of an Nvidia based Mac product (like some of the MacBooks) and do a external drive boot with my SSD to reset my kext cache. I would try it with my other iMac with an AMD 6970M, but it doesn't seem to work on that machine.

I don't have brightness control or the EFI boot screen, I don't mind this, but not being able to restart sucks. Can anyone help me with this?

I've been a long time lurker and would have to say that this site has some really great resources so far!

I believe I'm on Sierra 10.12.1 for my A1312 with an i7 2600S.
« Last Edit: February 28, 2018, 02:59:02 PM by DrChau » Logged
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« Reply #1 on: May 30, 2018, 02:55:39 AM »

Double good news on this.

We are FINALLY developing some iMac MXM Nvidia cards. It hasn't been easy, Apple doesn't offer any help, of course, and nobody else has succeeded at this.

Also, for folks in your spot, an eGPU would solve your boot issue. Even if it was typically for another machine, if your iMac has Bolt, yopu can use one.
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DrChau
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« Reply #2 on: June 23, 2018, 07:22:11 PM »

Sorry for the late reply as I was beginning to accept that there is basically no easy way around it.

eGPU would be nice, if the housing were easy to find at a reasonable price.

I will start looking for one! Thanks!
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« Reply #3 on: June 23, 2018, 10:19:25 PM »

Hi, m maybe you can take a moment and type up so more details?

I don't understand exactly what you are describing in first post

I will have a 770M here soon to test in 12,1
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DrChau
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« Reply #4 on: July 18, 2018, 11:21:17 PM »

Sure I can give a bit of context.

So I purchased a Dell Alienware branded GTX 770M (MXM) card for my A1312 i7 2600s iMac since I had a 6970M ATi video card. The card at first was not working on El Capitan until some updates to the plist KEXT to add the MAC ID to the KEXT. It worked like a charm up until more recent updates of Sierra OS (within 10.12.1). I had the mini DP/Thunderbolt output working for my iMac (haven't tested recently) as I'd tested a thunderbolt to HDMI out to a  BenQ Gaming monitor I had at the time.

So the issue is now since updating to the latest security patches with Sierra OS, is that if I restart my computer I can't boot it up as it will not go to the Apple loading logo UNLESS I take my SSD out of my computer, plug it into a MacBook Air also with Sierra OS 10.12.1, boot into my OS externally, and run the following commands making sure SIP is off;

sudo kextcache -system-prelinked-kernel
and then run this after it is done
sudo kextcache -system-caches

Now if I run the above commands while running my current hardware in my iMac, I get an error that says "Untrusted kexts are not allowed", but if I run it on the MacBook Air as mentioned, it works perfectly fine.

It's been months since I've actually updated or restarted my iMac. Hell I even put it on a UPS just in case there is a power outtage while I'm gone, just to make sure it will not shut down or restart unexpectedly.
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highvoltage12v
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« Reply #5 on: July 19, 2018, 04:24:04 AM »

Hello,
First let me start out that.I have been running high Sierra on my iMac with a 780m installed. What you need to do is have your first partition on your drive one that you never modify. You always need this partition to work in order to boot into other OS's/installers. For solving the modified kext issue, you need to burn high Sierra to a flash drive. In the OS you are booted into now, go to system prefreneces choose a startup disk and select the high Sierra installer drive. Your system will reboot into the high Sierra installer. Open terminal and type csrutil disable. While booted change your startup disk from the Apple menu back to your previous OS. I never used Sierra with the 780m installed because I was aware of having to modify applegraphicsdevicepolicy every OS update. If you were to install High Sierra I believe you will run into issues because your iMac can't update the EFI for APFS support. Id try to find a version below 10.13.4 .

Rominator, I pulled my EFI flashed gtx 970 from my Mac Pro and it installed into my akito node thunder 2. It doesn't display my iMacs EFI startup screen. It doesn't display video either when patched with the egpu.io purge Wrangler. The card will show up in system profiler /graphics, same goes for my rx480. I believe with the 780m installed ePGU's aren't functioning properly since this setup was working before my 780m swap. This was with "sudo nvram enable-legacy-orom-behavior=1" added.
« Last Edit: July 19, 2018, 05:51:34 AM by highvoltage12v » Logged
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« Reply #6 on: July 21, 2018, 10:30:15 PM »

EFI for Classic Mac Pro isn't same thing as EFI for eGPU.

It's like French, Spanish, and English. The EFI has a few similarities, but for most part is invisible to non-similar system.

All I have managed with 780m iMac rom is the boot screen. Certainly makes life easier vs. black screen at boot, but many things to still finish. Not sure when I will have time to finish.
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