3 ms·
Indeed, but the manufacturer doesn't promise anything-- for all you know the next processor generation or even microcode revision could change that. It would b
by nullc 2y ago
Indeed, but the manufacturer doesn't promise anything-- for all you know the next processor generation or even microcode revision could change that.
It would be nice for processor makers to explicitly specify that the common arithmetic instructions will take time which is constant in terms of their argument data.
- pclmulqdq 2y agoThey are explicitly specified by all major CPU vendors. https://www.intel.com/content/www/us/en/developer/articles/technical/software-security-guidance/best-practices/data-operand-independent-timing-isa-guidance.html https://www.intel.com/content/www/us/en/developer/articles/t...
- nullc 2y agoTIL -- wasn't the case a number of years ago.
- adrian_b 2y agoNowadays the manufacturer must promise that at least a well-defined subset of the instructions have an execution time independent of the operands. See the comment above by "cokernel_hacker", which provides links to the Intel and Arm documentation of this feature.