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What are the reasons the hardware the microcode is running on isn't directly exposed to the user? Why shouldn't we teach our compilers to generate code for the
by madez 9y ago
What are the reasons the hardware the microcode is running on isn't directly exposed to the user? Why shouldn't we teach our compilers to generate code for the lowest level possible?
- wmf 9y agoBackwards compatibility is a big reason. If the OS handles everything then you can only use an OS that has the latest drivers. Driver bugs could also brick your hardware in some cases.
- dfox 9y agoThere is actually an significant technical issue with user-supplied microcode on modern fast CPUs: the control store is not fully writable and only small parts of it can be patched in the field. Reason for that is that the control store is probably the fastest block of memory in modern PC as it has to have latency on the same order as CPU clock period and usually has very wide data bus. Implementing this as entirely writable RAM would be uneconomical.