I've heard from various people that programmable Ethernet cards exist and are easily available. However I have yet to be able to track down one of these mythical devices so I'm wondering if they're just that - a myth.
Such a programmable card has a gigabit Ethernet interface, has a programmable CPU and connects to the host system via PCI Express. The problem area these cards address are low latency network applications where the card itself does the work and "reports back" to the operating system. Basically the card acts as a co-processor and handles all the low latency requirements on the card, thus avoiding the issues of writing low latency code in user-land - think 0.4ms - 0.5ms response times.
So my question is, do these cards really exist and if so, where can I get my hands on one?
Bigfoot Networks makes a series of products (their Killer line) that are "smart" NICs: e.g. the Killer 2100.
It's not clear at a glance whether their current products are user-programmable. However, a review of a legacy product of theirs suggests that you were able to load specialized "apps" onto the cards, at least.