The basic eGPU hardware guide (for Macs)
(this guide will be continuously updated and improved to add and correct informations)
(Please feel free to comment and help gathering informations regarding the hardware topic)
Because of a lot of basic questions regarding possible eGPU hardware I will try to answer most of the questions in this thread.
The AKiTiO Thunder2 is currently the mostly used enclosure to run an eGPU on the Mac and because of that a lot of informations will be based and for the Thunder2.
This guide is a extension of Tech Inferno Fan general guides:
List of current builds and benchmark results:
GPU power basics:
The power consumption of current graphic cards can vary between 60-350W.
Because the PCIe slot can only offer max. 75W, the additional power can be gained from:
- 6-Pin PCIe plugs = max 75W
- 8-Pin PCIe plugs = max 150W
The 75W for the PCIe slot are only provided for PCIe slot, which are designed to host graphics cards. The normal standard for PCIe slots sets the limit to only 25W. That is also the reason why some enclosures only have low power power supplies, because they are designed to only host „non graphic cards“.
The possible enclosures:
- AKiTiO Thunder2
- Sonnet III-D
- OWC Mercury Helios (basically the same as the Thunder2, but with a better PSU. Unfortunately more expensive!
- Netstor NA211TB
Sonnet - Echo Express III-D Thunderbolt 2-to-PCIe Card Expansion System
2014 15" Macbook Pro Iris + GTX980@16Gbps-TB2 (Sonnet III-D) + Win8.1 [MrHaPPyPiLLs]
AKiTiO Thunder2 PCIe Box | PCI Express Expansion Box with Thunderbolt 2 Interface | AKiTiO
The AKiTiO Thunder2 is currently the cheapest way to make an eGPU setup (link zu 1.Seite Thread) and can be ordered directly from the manufacture for 189$+shipping. The AKiTiO offers a physical x16 PCIe slot, which can host any graphics card. The Thunder2 itself is shipped with a 60W power supply and not enough to power any current graphics card.
The Sonnet III-D is the easiest way to set up a eGPU, but also the most expensive one. It’s case can host long GPUs and with it’s 300W power supply it can also power the cards directly. In the original configuration the III-D has an additional 6-Pin PCIe connector to power mid range graphic cards. To get more PCIe connectors, the III-D has to be opened and additional cables have to be connected to the III-Ds PSU.
The choice of the graphics cards:
The Sonnet III-D can host long graphic cards, but is limited in the height and width of the cards. The graphic cards shouldn’t be higher than 2 slots and not wider than the reference cards of e.g. Nvidia.
The AKiTiO Thunder2 can host any graphic card, if the case is left open and modified by bending the front section.
But there is also a variety of small graphic cards that can fit into AKiTiO and enables to close the case. Still the selection of possible small GPUs is limited to max. a Nvidia GTX 970.
Possible cards are listed here: http://forum.techinferno.com/enclosures-adapters/7205-us%24189-akitio-thunder2-pcie-box-16gbps-tb2.html
Cards that enable to close the AKiTiO can’t be too wide and by that the choices are limited:
- EVGA GTX 960 (the one fan version)
- Galaxy / KFA2 GTX 970 Gamer OC
- Inno3D GeForce GTX 970 ot 960 Combat / HerculeZ X1 (the one fan version)
- Zotac GeForce GTX 970 without the fan shroud
The choice of the correct power supply:
In theory any power supply that can provide 12V can power the GPU. Currently there a two recommended kinds of power supplies:
- PC PSU (like for regular desktop computers)
- Dell DA-2 (an external power supply with 220W)
Most graphic cards don’t need more than 300W and by that any stronger power supply should work. That is wrong! Especially when it comes to desktop PC power supplies. The power supplies need to provide that specific amount of power on the 12V rail, that will power the GPU. It also needs to provide the correct plugs to power the GPU, which are 6-Pin and/or 8-Pin PCIe plugs. Because of that it is crucial to know which PCIe plugs the GPU you want to use needs.
E.g. GTX 970 cards need 2x6-Pin PCIe plugs which is only provided by PC PSUs with at least 450W.
Modern cards like the GTX 900 series can change the current state of power consumption multiple times per second and even exceed the normal consumption.
The Dell DA-2 is an exception, because it can provide 12V and 18A = 216W in total. This 216W can be totally used for the GPU and can even power an AKiTiO Thunder2.
It is important to keep in mind that you HAVE TO use only ONE PSU for the whole system. Please don’t mix two PSUs in this setup, because that can cause ground loops and damage hardware.
Using the Dell DA-2:
The Dell DA-2 provides a 8-Pin plug, which has the same size as a 8-Pin PCIe plug. It is important to know that the layout of the pins and the pinout is different, so adjustments have to be made.
An easy approach is to use 6-Pin PCIe y-cable, because they can easily be connected to the DA-2 with a bit of pressure. To make the DA-2 a connection or switch has to be installed between the remote Pin and any Ground pin.
If soldering is an option you can connect all 12V pins to one bigger cable and all ground pins to one cable. If you are doing that, please use proper wires that are thick enough to carry such high loads!
The Dell DA-2 discussion can be found here: http://forum.techinferno.com/enclosures-adapters/9426-220w-dell-da-2-ac-adapter-discussion.html
A ready to go cable can be found on eBay: http://www.ebay.com/itm/Akitio-eGPU-8-PIN-TO-2-x-PCI-E-6-PIN-super-low-profile-no-latch-1-x-BARREL-/261932428549?pt=LH_DefaultDomain_0&hash=item3cfc63ad05
Using a desktop PC PSU:
To use a desktop PC PSU you need to apply the „paper clip trick“ to make the PSU start. Simply connecting all plugs and switching it on doesn’t work!
PC PSUs are designed to start, when the User is pressing the start button on it’s computer. Because we are not going to use the PSU inside a computer, there is no switch and motherboard connected to it, to signal it to start.
The paperclip trick is creating a short circuit between the remote pin and a ground pin on the 20/24-Pin ATX plug that would normally be connected directly to the mainboard.
Alternative ways to power on the PSU are the use of:
- a SWEX (ATX Power Supply Power-On Switch)
- a Bitspower 20 PIN ATX
Keep in mind that with the paper clip trick, the PSU will always be turned „on“ and needs to be switched on/off by using the switch on the back of the PSU or using a power socket with a switch.
Powering the AKiTiO Thunder2 with an alternative power supply:
The Thunder2 only needs 12V to make it work. So a desktop PS PSU or even the Dell DA-2 can be used to power the Thunder2. To provide power to the Thunder2 12V and ground can be directly soldered to the Thunder2s PCB.
Another option is the use of a barrel plug to connect to the original socket on the back of the Thunder2. The barrel plug has to be connected to 12V and Ground of the used power supply.
The barrel has to have this dimensions:
inside 2.5mm (12V)
outside 5.5mm (ground)
A plug that doesn’t need to be soldered is a barrel plug with screw terminals. Here you just need to stick in the wires (without isolation) to make an electric connection.
The barrel plug discussion can be found here: http://forum.techinferno.com/enclosures-adapters/8317-%5Bguide%5D-making-molex-barrel-adapter.html
Using an enclosure/case to host big cards and desktop PC PSUs:
There is a way to store all your used hardware in common PC cases. I created a thread with ITX cases that will allow you to store all the devices inside a case: http://forum.techinferno.com/diy-e-gpu-projects/8675-egpu-cases.html
Please keep in mind that you will have to make modifications to the case in order to place in the AKiTiO Thunder2 PCB and the GPU together inside the case.
There is a way to relocate the PCB away from the GPU: a flexible riser.
Riser can be used to extend the PCIe port and connect the GPU in more ways.
Riser may cause problems:
- degeneration of the signal
- stability issues
- no working setup
This is because there are a lot of very cheap riser cables on the market with very poor quality.
Powered riser have been a recommended in the beginning of the eGPU discussion, but are currently focused on causing stability problems.
This is because of poor quality and cheap material used to moddify risers. These riser are able to power the AKiTiO through the slot and also the GPU.
We strongly advice you to not use a riser, unless you really have to!
We strongly advice you to power the AKiTiO Thunder2 with the barrel plug mod, earlier discussed!
- which GPU are you using?
- has the GPU the correct size to be placed inside the AKiTiO or do adjustments to the case have to be made?
- how many PCIe power plugs does the GPU have (6-pin or 8-pin PCIe plugs)
- does your PSU of choice have all the required PCIe power plugs?
- are you using just ONE PSU to power the enclosure and the GPU?
- is the paper clip trick used to "power on" the PSU?
- is the AKiTiO Thunder2 powered?
Q: What is a barrel plug?
A: A barrel plug is a barrel shaped plug to power low voltage electronics. There are different plugs in size and the used voltage (12V or 19,5V).
The AKiTiO needs a 5.5 and 2.5mm barrel plug.
Q: What is a PCIe power plug?
A: Because graphic cards need a lot of power, the additional power is provided by PCIe power plugs. The common plugs are 6-Pin (75W) PCIe and 8-Pin (150W) PCIe plugs and are mostly found on desktop PC PSUs.
Q: What is a Molex plug?
A: The most common Molex plug is the 4-Pin Molex, that was used in the past for HDD and optical drives. That plug can be found on Desktop PSUs.
The Pinout of the 4-Pin Molex is 1x yellow = 12V ; 2x black = ground ; 1x red = 5V.
Q: What is the paper clip trick?
A: The paper clip trick a way to trick a PC PSU to start without using a computer or motherboard. Please keep in mind that using the paper clip trick requires a power consuming device to be connected to the PSU if it is turned on. DO NOT start the PSU without any device attached after applying the paper clip trick.
Q: What is PCIe?
A: PCIe is PCI Express („Peripheral Component Interconnect Express“) connection slot to electronically connect computer cards.