On Sat, Jun 24, 2017 at 9:55 AM, Bluey bluey@smallfootprint.info wrote:
Please excuse my ignorance in such matters but would it be possible to use a RISC-V or FPGA chip as an interim eGPU until such time that a more specialised chip can be developed and released?
on its own (as-is), no. however with certain very very specific and in some cases specialised SIMD instructions a reasonable approximation can be had. these operations are:
* SIMD "and" for a bit-wise zero check (as large as possible) * inverse-squared function (for 1/x^2) - a very common operation in 3D * SIMD 12-14 bit accurate divide operation.
this latter turns out to be "good enough" for the majority of 3D operations, where the accuracy on screens which only *have* 1920 pixels (11 bits being sufficient) division calculations beyond 12-14 bits is completely and utterly redundant... *under certain circumstances*.
the point being that a divide operation which only requires 12-14 bits of accuracy may complete in half the time, thus dramatically saving on CPU cycles.
I appreciate that RISC-V/FPGA chips are not likely to be well-suited to the task of GPU processing but perhaps they would be better than no GPU at all.
not "and be power-efficient at the same time"
Once a specialised libre GPU has been developed, the RISC-V / FPGA chips could be repurposed as a CPU for other projects/computers/laptops/etc. and, hence, ensuring that they don't go to waste.
this was the reasoning behind ICubeCorp's "UPU" - Unified Processing Unit - which unfortunately they kept proprietary. i tried to help them to understand the need to release the full boot initialisation source code and to comply with the GPL but they did not follow up.
l.