Advice from Mike Giles: updated April 2015
I am sometimes asked which NVIDIA GPUs to buy for scientific computing using CUDA. My current advice is:
a) For initial development, start with a PC with a GTX 750Ti card. This has the latest Maxwell GPU, uses only 60W, will fit into most PCs, and costs around £100 from suppliers such as dabs.com or scan.co.uk. For the best performance, put it in a PC with a 16x PCIe gen 3 slot.
b) For production computing requiring good double precision floating point performance, move to the Tesla K80 card which has 2 GPUs, each with 12GB of memory. The Tesla units are produced by NVIDIA with tighter quality control which is why they cost significantly more (currently around £4k, but contact me for prices and Oxford discounts) than the GTX cards. Supermicro has a range of GPU servers which can hold 2-4 Tesla modules within a 1U or 2U server.
c) For single precision production computing, the best choice is probably the new GTX Titan X card. This has 12GB memory, very good memory bandwidth and great performance, and costs around £1000, which is about half the price (per GPU) of the K80.
Power connectors for NVIDIA cards
All of NVIDIA's high-end cards require one or more PCI Express power connectors. These come in two flavours, 6-pin and 8-pin. Some low-end cards require just one 6-pin connection, while the most powerful card requires two 8-pin connections. It used to be difficult to find out what each card used, but now you can find out by going to this GeForce family page, selecting the card of interest, and then the Specifications tab, and then scrolling to the bottom.
|Card||PCIe power connectors|
|GTX 750 Ti||none?|
|GTX 980||2 x 6-pin|
|GTX Titan X||6-pin + 8-pin|
|Tesla K80||2 x 8-pin|
Most new power supplies offer at least one 6-pin connection, and quite a few provide an 8-pin connection.
A lot of graphics cards come with adapters to convert the connections offered by an existing power supply to what you need. In particular, the GTX980 may come with an adapter like this to convert two 4-pin molex supplies (for disk drives) into one 6-pin PCI Express connector. This enables you to install the GTX980 in a system which has a power supply with only one 6-pin connector.
Note also that you will need a large power supply for high-end GPUs, at least 600W and even more if you have multiple cards.