ithildin

Yeah I can see why it's easy to confuse the mini DisplayPort and Thunderbolt cables - just keep an eye out for the Thunderbolt symbol on the plug. In terms of GTX 970 vs 980, it really depends on how much gaming you will be doing and at what resolution. Looking at your monitor/laptop, I'm guessing most of your gaming will be done at 1080p. The GTX 970 is more than enough to get max framerates at 1080p on most games and it's the option I would recommend unless you're planning to upgrade your monitor to 1440p or beyond. That being said, coil whine and the 3.5 + 0.5 GB issue make the GTX 970 less appealing in the long run so if you have the funds to spend on a GTX 980 and see yourself upgrading your monitor in the next year or so, go for it.

The mini yellow/black power cable connecting the two AKiTiO boards looks weird in your picture, almost like it's cut. Can you confirm that it's intact and connected? The blue LED on the AKiTiO is indicative of a Thunderbolt link being established and it should turn on as soon as you machine boots up while connected to the AKiTiO box, even without a GPU. Try connecting the AKiTiO with its original power brick and just the Thunderbolt cable (no ATX PSU, riser cable or GPU) and try turning on the laptop - the blue light should turn on. If it doesn't then it could be a problem with the Thunderbolt connection.

I also didn't expect there to be a problem enabling Optimus on the Macbook Air, except it simply didn't work on Windows 8.1 (EFI) with most of the GPUs I tested (GTX 460, GTX 670, GTX 970 SC). I can get Optimus in OS X just fine but Windows 8.1 disables the iGPU on boot, after briefly flashing the blue Windows logo. Once it loads, the Intel HD 5000 adapter is gone from Device Manager - only the eGPU is listed. I tried all the tricks listed here in the forums (e.g. powering the GPU after the MBA startup chime or at the bootloader screen when you press alt/option key, hotplugging the GPU into the AKiTiO, etc.). The only thing that worked was Evo*'s modded EFI but it also disables the keyboard and touchpad and locks the CPU SpeedStep multiplier to 13x (1300 MHz), which is a dealbreaker. There are substantial differences under the hood between the 13" MBA and the 13" Iris MBPro that affect how they handle eGPUs , which is why I'm ecstatic after finding out how well GTX 970 FTW+ works with the MBA under Windows 8.1.

On the Macbook Air under Windows 8.1 or Macbook Pro?

Another quick update - I've figured out that the GTX 970 FTW+ is the critical component to enable Optimus on my set up. I've tried using my GTX 460 and couldn't get Optimus to work, despite several attempts and using the latest drivers. I replaced the GTX 460 with the GTX 970 FTW+, reconnected everything and Optimus worked right away. Thus, Optimus was not enabled by an update or a new Nvidia driver version. I can only conclude that there is something specific about the GTX 970 FTW+ card (perhaps the VBIOS) that allows for Optimus to work with the Macbook Air, either because it's more flexible in terms of resource allocation or somehow tricks the MBA's EFI to keep the iGPU active. The fact that I could get Optimus to work with the EVGA GTX 970 FTW+ but not with an older GTX 970 model (GTX 970 SC, 04G-P4-2977-KR) is curious. The GTX 970 FTW+ is a second generation GTX 970 from EVGA with a number of improvements, including extra power phases (higher max TDP) and a physical VBIOS toggle switch (like the silent/Uber switch found in the AMD R9 290X). Either VBIOS setting (dBi or FTW performance) works with Optimus - perhaps it's this custom EFI VBIOS design that makes Optimus on the Macbook Air possible.

OK I ran a few more experiments and it turns out that the PCIe power cable is not an issue. The boot state (Optimus vs. external monitor only) of the eGPU is what determines the numbers in Firestrike. When I tried to revert driver versions, I noticed that the system reverted back to the old behaviour (disabling the iGPU upon boot) and kept working like this until I powered the Macbook Air down AND disconnected the Thunderbolt cable. Once everything is disconnected and reconnected, the next system boot will have Optimus enabled. Here is a summary of what I have done: Switched drivers between 9.18.13.4752 and 9.18.13.4709 Alternated between using one or two separate PCIe cables to power the GTX 970 FTW+ Changed between Optimus to eGPU-only (iGPU disabled) boot modes I ran Firestrike on all combinations of driver version, power config and boot mode. The conclusion is that in Optimus Firestrike scores are >6000 whereas in iGPU disabled mode the scores drop to ~4000. Driver version or power configuration had no influence in these results. Despite my initial concerns, powering with a single PCIe power cable seems to be OK - the image flickering I had noticed before was simply Windows 8.1 silently updating the GPU drivers. I didn't test the two power configurations too extensively but I saw no difference in the Firestrike results. I currently don't have a good explanation for why the system takes such a performance hit when running with iGPU disabled since the FTW+'s predecessor, an EVGA GTX 970 SC ACX 2.0, got >6000 on Firestrike without Optimus. In both cases, PhysX was configured to used the GPU and nothing stood out from monitoring the card using GPU-Z during the benchmarks. It is possible that this behaviour is specific to this specific card but I'm not sure why/how. Optimus working on the Macbook Air cannot be attributed to the new Nvidia drivers (v9.18.13.4752) since it also works with older drivers (9.18.13.4709). Instead, Optimus may have been enabled by another Windows update (e.g. KB3000850) or due to a particular feature of the VBIOS on the GTX 970 FTW+. Reverting a cumulative Windows update can be tricky but I can easily test the latter hypothesis by trying to get Optimus to work with my GTX 460.

It's hard to say - Windows was clearly recognizing that a second GPU was connected because the iGPU was disabled right at the Windows logo stage. It's just that I never got image back, either on the Macbook display or on the external monitor hooked up to the R9 290X, so I'm guessing it failed to initialize. I tried blindly typing in my password to see if it would log in but I didn't hear any sound from the speakers or see the keyboard backlight coming on so I assumed it crashed. On OS X, there was no issue booting it up so I think the issue is specific to Windows & Intel GPU drivers and how they behave by default on the Macbook Air. In fact, when I tried to use an Intel NUC, the R9 290X was initialized on boot but I still had picture from the iGPU and thus could log in and install Catalyst drivers as per usual. I tried hooking the R9 290X directly to the AKiTiO while powering the PCIe slot with a DC barrel adapter but it didn't seem to make a difference.

I've realized that there are two variables at play here, the power configuration and the new driver (9.18.13.4752 vs. 9.18.13.4709). I'll try changing back to the old power config (just using the blue PCIe cable for 6+8 pin PCIe power) without touching the driver and see if the loss of performance is still present. The reason I am still convinced it's a power issue is because I ran a EVGA GTX 970 SC (6+6 pin PCIe power) with the old drivers + single PCIe power cable and the Firestrike results were very similar to what I'm seeing now (6083). I shipped the GTX 970 SC back to EVGA in order to Step Up to a 970 FTW+. Once the new card arrived, I connected it with a single power cable as before (8+6 pin PCie power) , ran Firestrike and immediately noticed the low scores. After closing 3DMark and using the desktop, the display flickered on/off a few times - it was odd and seemed like the there was something up with the GPU. When I opened the case, the PCIe power cable was warm to the touch so I guessed that was the issue. I changed the power config to split the load across two different cables, re-tested and all the numbers improved. I've sold the GTX 670 FTW but still have the R9 290X. Yes, the R9 290X fails to boot with my Macbook Air but only with Windows 8.1. I've tried pre-installing AMD's boot camp driver - made no difference. I've also tried Evo*'s mod some time ago but it screwed up with the MBA's keyboard/touchpad and Intel Speedstep so I reverted back to vanilla EFI. The R9 290X boots well with either Macbook Air + OS X Yosemite or with Intel NUC + Windows 8.1. In both of these cases, the GPU is not stable though - it crashes with high demand apps. I haven't yet tried the taping trick - maybe this will help.

Quick update on this project: I replaced the GTX 670 FTW with a GTX 970 FTW+ and stability has improved by leaps and bounds. The system is now completely stable and performance is great! With the latest Windows updates (Feb 2015) the Intel GPU on the Macbook Air is no longer disabled at boot so Optimus is now possible without compromising any functionality. Here is a snapshot of Optimus in action: External monitor Internal (Optimus) Performance ratio (int/ext) 3DMark Firestrike (graphics score) 6206 (10440) 5787 (9051) 93.2% (86.7%) Unigine Valley (Extreme 1440x900) Score:2350 FPS: 56.2 Score:2322 FPS:55.5 98.8% The performance hit seems minimal, at least on these synthetic benchmarks, and arguably negligible considering the benefit of not requiring an external monitor. I will add some gaming benchmark results but these first set of numbers are very promising. I've rebooted the machine several times just to confirm Optimus was robust. I will try to revert the drivers back to their previous state to confirm that these were indeed what enabled Optimus. A small side note for users trying the GTX 970 FTW+ with an ST45SF-G power supply - even though the provided PCIe power cable comes 6 and 8 pin plugs, it's not capable of powering this GPU on its own. I left the PCIe cable hooked up to the 8 pin socket and used a separate power cable + molex-to-6-pin converter. As a result, 3DMark Firestrike went up from 4014 to 6206. See post below for updated info on FTW+ performance loss.

Exactly. The AKiTiO Thunder2 is clearly not meant to deliver 75W to the PCIe slot - it may work on some scenarios but it's clear that some modifications (ATX->DC barrel mod or alternative power brick, soldering extra capacitors to improve power filtering, etc.) are required to provide reliable power to the PCIe slot through the DC jack . Besides, if we are thinking about the average user not wanting to make his own DC barrel plug mod or solder power wires to the AKiTiO board, then a powered riser cable is a much simpler solution that is far from "silly".

I'm curious about your 670 FTW. Is it a 02G-P4-2678-KR like mine or one of the updated models that were released later (FTW SIG2 or FTW+)?

That's good news but perhaps not surprising since you're using a GTX 980 - there have been no reports of stability issues with any of the 900 series GPUs. Like @GTX 760), to frequent crashes (GTX 770, juniordiscart hasn't had experienced issues to the same extent with his GTX 760 which is essentially a rebranded GTX 670. I agree, since these issues we've been seeing are likely GPU make/model specific, we should keep track of all GPUs reported to give problems with the AKiTiO Thunder2. Time permitting, I'll try to compile the different reports we've seen here, chase up with the OPs and post the summary.

In principle, yes. You could wire them up in a couple different ways: you could either make two separate boxes, each of them with its own AKiTiO + PSU and connect them using two TB cables in a daisy chain or instead go for a large box with a single PSU + two GPUs + single AKiTiO with PCIe cluster or two AKiTiOs. Either way could work. One key question is whether it's possible to set up SLI/Crossfire between GPUs hooked up to different TB-to-PCIe adapters - AFAIK all SLI/Crossfire eGPUs reported here used a single TB device (Sonnet or Netstor) connected to 2 or more GPUs but that doesn't necessarily mean it isn't possible.

Dual GPUs with either AKiTiO+PCIe cluster or daisy-chained AKiTiOs would be pretty cool but keep in mind that a ST45F-G (450W at 87% efficiency = 397W) doesn't have enough juice to power both a 7950 and a 7970 simultaneously in a stable manner (240W + 300W TDP respectively). You'll need a >600W ATX PSU - I don't think the SilverStone SX600-G will cut it either.

I agree that SFX-L PSU models are currently the best option for a small form factor case PSU. The benefits of having a 120mm fan over a 80 mm one are unquestionable. That being said, what SilverStone is not saying in that statement is that cost saving concerns play a significant role in engineering decisions, something that was clearly obvious from the V1.0 of this same PSU, where they chose to fit it with a higher RPM lower torque fan that was cheaper at the expense of being noisier. All things considered, the Noiseblocker fan is probably too costly for a PSU with a $99.99 price point. Instead, this is a good mod option for someone wanting to adapt an existing PSU to use in a HTPC or other scenario where 33db/A of fan noise is not acceptable. The number of successful mods reported on HardForums and elsewhere argue that it's a stable mod and works especially well for reducing fan noise under 350W load which is where most eGPU implementations would fit.The real risk here is electrocution if one is not careful to discharge the PSU properly before opening it up, but it can be done safely like shown in @Phantron's recent implementation.

I also have a V2.0 ST45SF-G. Supposedly the fan speed profile has been updated on v2.0 to be quieter but I still find it a bit too loud. There is a mod that replaces the stock fan with a quieter Noiseblocker one (see discussion here). PSU warranty will be void and one has to make sure the capacitors are fully discharged (>24h unplugged) before opening the PSU but the mod itself seems pretty straightforward. V1.0 with stock fan V1.0 with Noiseblocker fan Parts needed for mod: 3-Pin Standard Fan Connector (Male) to Mini 2-Pin GPU Fan Connector (Female) Noiseblocker NB-BlackSilentPro PC-P 80mm x 15mm Ultra Silent PWM Fan - 2500 RPM

It looks like an 107C SMD Tantalum capacitor. You can get a replacement part from here. It's a polarized capacitor so make sure it's soldered in the same orientation as the original part (see pictures here). Like I mentioned before, it's likely that this is not the only damaged component on your AKiTiO boards. It's worth taking a closer look at both boards and checking for burned tracks or other damaged components. Some you can check with a multimeter, others (such as the ICs) won't be easy to check without more sophisticated equipment.

I've been puzzling a bit on the mod that @ha1o2surfer mentioned. I can only surmise that he hooked up the TB controller card to his PSU in addition to the powered molex. Even though I haven't modded the small TB controller power cable, I've tried connecting my PSU to the DC jack + PCIe riser + GPU simultaneously and the GTX 670 still crashed as per usual. Looking carefully at the PCB traces surrounding the DC jack and the mini power cable connector, it doesn't look like there's much there besides some condensers to provide some current filtering: It looks like the mini cable is just feeding 12V to the TB controller card, which means hooking up power to the cable or to the DC jack should give similar results. Bottomline, I think my modded molex-to-DC barrel adapter should be equivalent to ha1o2surfer's modded TB card power cable. It didn't improve matters for my setup but maybe it will help people with Macbook Pros. If you want to test it out and need your own molex-to-DC barrel adapter, @jacobsson has a nice mod guide here. Be extra careful with polarity when wiring it up! The center contact on the DC barrel plug must be connected to positive (yellow cable)!

Ouch! Looks like one of the condensers on the TB card is fried but there's probably more damage elsewhere. I hope your GPU is still OK.

By the way, it was @ha1o2surfer that modded his Akitio daughterboard mini power cable, not me. Like you, I would love to find out exactly what he did and how it stabilized his Akitio eGPU.

I'm not sure what you mean by me having found a solution. My Macbook Air + AKiTiO + EVGA GTX 670 2GB is definitely not stable (no Optimus either). Like for @juniordiscart , my GTX 460 is more stable but I've noticed that Windows 8.1 is occasionally unresponsive. I've been busy at work and I haven't gotten around to testing the setup again to look for MEIx64 entries in the logs. I should have some time for this tomorrow. EDIT: I think you got me and @ha1o2surfer mixed up:

I haven't had time to test my setup with unstable vs. stable GPU but I looked at over 1000 entries on my Windows logs concerning MEIx64 and none of them were "Warnings", even though I' consistently having problems with instability when using a GTX 670 card. Since my laptop is a Macbook Air and that I haven't found a way to enable Optimus, I think the MEIx64 warning is a particular symptom of Macbook Pros somehow struggling with dual GPU mode. By the way, MEIx64 is part of Intel's Management Engine Interface drivers, which interacts with the ME firmware in the BIOS. Have you tried updating your Intel drivers? @ha1o2surfer , I'm also interested in your daugther card power cable mod. Could you give us more details?

Sounds like a good idea, especially since I've also been struggling with a GPU-specific instability with the AKiTiO Thunder2. I'll check my setup tonight and will report here.

I've just done another round of tests with the GTX 670 directly connected to the Thunder2's PCIe slot. Additional PCIe bus power was provided through a modded DC barrel plug hooked up to the PSU. This time, I tried to mechanically stabilize all PCIe connections: between the GPU and the Thunder2 PCIe slot as well as between AKiTiO's TB controller + daughtercard. I secured both AKiTiO's cards firmly to a custom acrylic tray, mounted the GPU horizontally above the Thunder2 and braced it as well as I could. The system boots fine with the GTX 670 but the stability problem remains unresolved - I got a massive slowdown spike halfway through the first run of FireStrike and Windows crashed and rebooted soon after. Thinking that my GTX 670 picked up a problem during my eGPU experiments, I plugged it back into my desktop rig and tested it by running Firestrike continuously - no issues after about 1h so the GTX 670 is fine. I've been also trying to hook up my AMD R9 290X to the Thunder2. For some reason, Windows won't turn on the external monitor when the 290X is hooked up, with powered riser cable or when I connect the GPU directly to the Thunder2. On the other hand, OS X Yosemite boots just fine with the 290X so it must be a Windows issue. I've tried running Unigine Valley on Extreme HD on OS X. I can leave it running on a loop for over 30 mins without a problem but, when I start benchmarking, the system grinds to a halt as soon as it completes and the results on the screen...bizarre. I'll try to see if it's a specific problem with Valley or a broader stability issue. Next, I'll run some tests with the Thunder2 + GPUs hooked up to an Intel Thunderbolt NUC.

It's a great design! I'm really looking forward to your crowdfunding campaign. I understand that you are going for a high quality part with the 3M PCIe adapter but I'm guessing it's not powered unlike the ones most people here use for their eGPUs. Do you think you could sell the A4 case without the 3M PCie extender? I'm thinking of trying to fit a powered PCIe ribbon cable in the A4 and seeing if it's stable enough for a x4 PCIe 2.0 link. I guess modding the the 3M extender cable is also an option but the idea of trying to solder some power leads to a $80+ extender makes me a bit nervous.