Alarming0

Just going to keep speculating: Looks like the dGPU is being used to display the output from the eGPU because it shows a constant ~30% load. I'm guessing that using the eGPU being in use throttles the dGPU, perhaps allowing it to use more load is the solution here.

Update: Overclocking the iMac monitor shows that the framerate is being capped at 50% of the refresh rate most of the time. If only I could OC to 120hz lol

Hey everyone, so I've been trying to get my eGPU working on my girlfriend's iMac. An external monitor is working thus far, but of course I have run into the standard issues that people have while trying to run on the internal LCD on Macs with dGPUs (in my case a GT 750m). I used to run this eGPU on an Asus laptop (with Windows 7) via mPCIe and really wanted to use the internal screen in that case as well. One thing that DID NOT work for my previous laptop/eGPU was starting a game on the external monitor, setting it to windowed mode, and then moving the window onto the internal screen. On my laptop, doing this with e.g. afterburner open would let you watch the dGPU (GTX 560m) switch the load back and forth with the eGPU (GTX 950) (or split the load when you dragged the window onto both monitors). On the iMac in Win 10 Bootcamp this is not how it works, *switching the window between internal and external LCD continues to use the eGPU to render the game*, presumably engaging Optimus on some level and ultimately *just working*. I have confirmed the load on the eGPU to properly correspond to the expected load in the game as well as the GPU indicator task bar icon indicating that the eGPU is rendering the game. The issue however is that when you do this the GPU takes a massive performance hit. I cannot tell if this is just the effect of Optimus (because I can't run Optimus benchmarks like firestrike because that would require me to switch the monitor which I don't think is possible) or if there is more to this performance hit. We're talking basically a straight 50% of the framerate in multiple games despite the same load. Is this expected Optimus performance? I only have a GTX 950 so I don't know if perhaps people with stronger GPUs might see better performance in this case. Alternatively, I was thinking that because I am unable to install Intel Graphics Drivers there may be some functionality that is lost. Sorry if this has been discussed, I looked everywhere for other threads like this one without luck. EDIT: Ok after much testing I can safely say the following: The eGPU definitely continues to render the game and then transfers that to the iMac's internal screen. Doing this causes both the dGPU and CPU to throttle resulting in mostly unplayable experiences. If I can somehow stop this throttling I think this will result in functional eGPU on internal screen.

@Slovedon @3RYL Was wondering if either of you have plans to try a thunderbolt capture card as a solution to this problem?

Alright, well I will figure it out and post a full build once things get working. Thanks for your time!

@Dschijn Yeah, looks like I got insanely lucky. Only paid $50 USD for it and it has the exact same functionality as the Thunder2! Can you confirm that Optimus is disabled in Windows 10 on computers with dGPUs? Went to bed last night under the impression that the best course of action for running this eGPU via the internal LCD of the iMac is going to be via installing windows 8.1 instead of 10.

@Dschijn Here are the pictures: http://imgur.com/a/s4ju7 Still haven't gotten the eGPU going on the internal display but I've benchmarked it on an external and it is running exactly as fast as the same GPU on a laptop via hwtools PE4C (mPCIe). Had to use the PSU the PCB came with to power it and the akitio mod for a Dell DA-2 to power the 6-pin PCIe slot.

Having trouble emailing myself pictures from my phone so I will have to post pictures later when it ends up working, guess my mail is down. I disabled the 750m and it is clearly now running on internal graphics because everything is terribly choppy. What should I do now? Are there any guides out there or am I just missing something obvious here?

Sure, but be prepared to laugh at my setup. I will be putting this into a mini pc case once everything is properly working. But yeah, I've been looking around and haven't found a solution to my problem yet: how do I go about using the eGPU to power my iMac's (late 2013, GT 750m dGPU) internal screen. Is this even possible?

Well I just got the PCB in the mail 30 minutes ago and it works! One thing I am unsure of is how to get the eGPU to run using the internal LCD of the iMac though so any help with that is appreciated before I go calling this a complete success.

I should also mention that the article is 2 years and 1 month old now...

Well like I said, the article doesn't discuss the PCB specifically, just references it with a picture. It is not the same pcb that is in the Lacie box pictured at the top of the page (naturally): http://www.tweaktown.com/articles/6249/thunderbolt-2-ready-for-windows-with-the-asus-thunderboltex-ii/index4.html (It's on page 4 if it auto-redirects back to page 1)

Hey everyone, so I made the maybe unfortunate mistake of waiting until I had more free time to put together an Akitio Thunder2 build only to find out that 3rd party sellers are now selling it for $269. I was able to contact Akitio and they will sell one for $219 so if you are still in the market, that is the way to go. But while I was trying to decide what to do and waiting to hear back from Akitio I put a post up on reddit looking for a used one or just the PCB and found a guy who had something fairly interesting that I had never seen before. The person in question writes or wrote for tweaktown.com and had received an Asus Thunderbolt 2 PCB to write an article about. According to him, he went on to use the PCB for an eGPU via thunderbolt 2 on his macbook. I have been searching for this PCB online and the only place I can find it mentioned or pictured is in his article so I am starting to think he may be one of very few if not the only person with this pcb. Given that he said it was working for him as for an eGPU and that he was selling it super cheap, I went ahead and bought it off him. I've attached the picture from his article though I have other pictures that he sent me before I purchased it. Anyway, it will be arriving today so I'll post more info or pictures if/when I get it working. http://imagescdn.tweaktown.com/content/6/2/6249_20_thunderbolt_2_ready_for_windows_with_the_asus_thunderboltex_ii.jpg Note that the article isn't really about the PCB, but thunderbolt 2 and other chassis's so don't get confused by the url there, this is NOT the thunderboltex ii.

Ordering ready-to-use cables for Dell DA-2 and Akitio Thunder2 from AntronST: Send an email to [email protected] with the following information: Paypal email address Physical Address Phone number Part # / quantity The part numbers for the two different types of cables are as follows: 2x6-pin version ($20): Part #: AeGPU8P2PCIE6SLPBARREL 2x6+2-pin version ($24): Part #: AeGPU8P2PCIE6+2BARREL They will then invoice you for the cable. Antron have less than 10 of the 6-pins as far as I have gathered and a similar amount of the others so this will not necessarily last long. Good luck!

Alright, they invoiced me and I paid it so it looks like this is going through. Works out for me because I only needed the 2x6pin as opposed to the 6+2pins. I explained to them in the course of our communications that they are the only people making a ready-to-use cable like this one so they should consider selling them and that if they did I would help others get in touch with them. The process for ordering is simple and I will detail it in its own post below.