21–30 of 130 posts
Aren't FPGA's used mostly to test/design a circuit that you would then go on to actually fabricate/build? I could be wrong but I thought FPGA's were stateless (meaning if they powered off/reboot you loose everything and have to set it up from scratch again).
Aren't FPGA's used mostly to test/design a circuit that you would then go on to actually fabricate/build? I could be wrong but I thought FPGA's were stateless (meaning if they powered off/reboot you loose everything and have to set it up from scratch again).
Aren't FPGA's used mostly to test/design a circuit that you would then go on to actually fabricate/build? I could be wrong but I thought FPGA's were stateless (meaning if they powered off/reboot you loose everything and have to set it up from scratch again).
No, they retain state. We used an Altera DE1 in school and it retained our burnt in program until erased or reprogrammed
Aren't FPGA's used mostly to test/design a circuit that you would then go on to actually fabricate/build? I could be wrong but I thought FPGA's were stateless (meaning if they powered off/reboot you loose everything and have to set it up from scratch again).
FPGAs are often used to test/design not a "circuit" but an ASIC (application-specific-integrated-circuit) that you will then go on to actually build. Or, if your application doesn't have volume to suppprt the ASIC engineering costs but can support the FPGA unit cost, you just leave it as an FPGA. There are millions of devices (industrial machines, research, testing, etc) where this makes sense.
And not all FPGAs loose state when powered down. For those that do, there's typically an easy way to hook up a little Flash chip and bootloader to reload the state automatically on reset. For those that don't have that option (EG, currently working with an ABB robot, Mecco laser, and Rockwell PLC which all contain FPGAs, only the Mecco can boot itself), you store state in battery-backed SRAM and just leave the RAM on at all times.
Aren't FPGA's used mostly to test/design a circuit that you would then go on to actually fabricate/build? I could be wrong but I thought FPGA's were stateless (meaning if they powered off/reboot you loose everything and have to set it up from scratch again).
Yes and yes but new uses are emerging, it's like 3D printing: there's a crossover where the extra cost you pay for flexibility becomes too much to compete with hard wired logic despite the high initial cost.
"Intel does offer an emulator, so testing for correctness does not require this long step, but determining and optimizing performance does require these overnight compile phases." After some experience with FPGAs, the emulation step is not enough to test for correctness. Most of the problems happen while synchronizing signals with inputs/outputs and with other weird timing problems, glitches and unintuitive behavior…
"Intel does offer an emulator, so testing for correctness does not require this long step, but determining and optimizing performance does require these overnight compile phases." After some experience with FPGAs, the emulation step is not enough to test for correctness. Most of the problems happen while synchronizing signals with inputs/outputs and with other weird timing problems, glitches and unintuitive behavior…
There are a number of real issues with the emulation approach even now. Firstly, emulation isn't accurate - if you do floating point math in your application it will give you different results (within the tolerances of the OpenCL spec) on FPGA vs. CPU. So you can't test for correctness in the emulator. A second more serious issue is that getting performance that justifies using an FPGA requires tuning very carefully…
That seems like a gross weakness in the emulator; floating point isn't actually nondeterministic!
Earlier quoted context omitted.
No, they retain state. We used an Altera DE1 in school and it retained our burnt in program until erased or reprogrammed
Probably burned into an external EEPROM or flash, the FPGA fabric itself still has to be configured by some external means. It's pretty fast but on-the-fly reprogramming of the FPGA logic is still an issue where you want to very quickly switch the logic on the FPGA.