Can you reprogram the part of an FPGA that is actively being used?
An FPGA isn't really a "gate array," but a huge ensemble of small lookup tables that are made with what amounts to very fast static RAM. If major FPGA manufacturers didn't guard their bitfile formats with their lives, it's possible that entirely new fields of research would have emerged to find new ways to take advantage of the existing hardware in these chips, much like what GPGPU researchers have done with graphics cards.
I wonder how expensive it would be to make a really really tiny FPGA with a few tens of cells in it.
As in, I realize chip design is expensive and crazy complicated, but small runs are only around $5k or so. I'm wondering if FPGAs manufacturing has similar costs - or at least similar-ish enough to be potentially interesting.
If you could go from zero to tiny prototype FPGA with 5 or 6 figures, you might just be able to pull some VC money out of thin air to kickstart with. Or you might not even need to go in the VC direction, there's bound to be a group of people out there with collectively enough between them to kickstart something like this. I'm uncertain if Kickstarter would be a horrible disaster.
With prototypes made, you'd just need to send a few of the prototypes out to some smart PhDs and hardware hackers, get them to show what's possible, and that could be a viable way to get further investment and complete the bootstrap cycle.
Obviously the point of all of this is to make a chip that's as open as reasonably possible. Physical chip manufacturing is likely to be NDA'd (for example the SRAM would probably be supplied as a reference design from the foundry) but the "how to poke this with software" could be super open. Would be fun.
Why do they?
Especially at the high end, the manufacturers commonly introduce new hardware constructs -- high-speed transceivers, clock generators, memory controllers, that kind of thing -- and they don't really want to document and disclose the inner workings of these components at a level that would allow third parties to write tools for them. It could potentially take a non-trivial amount of documentation and customer support work. Meanwhile they want to preserve their trade secrets, and they also don't want to attract infringement suits from either patent trolls or legitimate competitors. Disclosure of bitfile formats would open those particular kimonos a bit too wide for comfort. This is largely why Linux users can only get GPU support via binary blobs.
At the low end, some good reverse-engineering progress has been made by people like Clifford Wolf on the Lattice parts. This work is certainly important, but as long as there's reasonably rapid technological progress on the hardware side, reverse engineering is never going to be enough to sustain a healthy third-party tools industry.
It's a real shame. Imagine how far we'd (not) have come if Intel and Motorola had walled off their instruction sets...