CPU Firmware
So, I've never really been one to understand things at the hardware level and generally don't understand how assembly works behind the scenes (which is probably a bad thing given some of my projects but I digress). I get by by just understanding that a certain op code does a specific action, it has X side effects I need to be careful about, and I need to remember any state it changes before calling the next op-code.
But CPU firmware has me confused. Opcodes, to my knowledge, are driven by hardware (AFAIK the CPU). Firmware can change support for certain opcodes and I don't understand how that works. Can anyone explain to me the place where firmware sits for the CPU relative to the opcodes I call from something like x86 or AMD64 assembly?
But CPU firmware has me confused. Opcodes, to my knowledge, are driven by hardware (AFAIK the CPU). Firmware can change support for certain opcodes and I don't understand how that works. Can anyone explain to me the place where firmware sits for the CPU relative to the opcodes I call from something like x86 or AMD64 assembly?
Maybe this is something your interested in learning about.
My old instructor claimed that CPU vendors are highly secretive about their microcode, so you can't really know much at all about it for a specific CPU. Basically, you can say that machine instructions aren't really machine instructions, they're actually a high level language interpreted by Microcode, which translates it into actual processor specific instructions. This makes it easier to use the same standard machine code for a whole family of processors, yet still integrate new high performance features and tricks in newer devices, etc.
| Microcode typically resides in special high-speed memory and translates machine instructions, state machine data or other input into sequences of detailed circuit-level operations. It separates the machine instructions from the underlying electronics so that instructions can be designed and altered more freely. It also facilitates the building of complex multi-step instructions, while reducing the complexity of computer circuits... http://en.wikipedia.org/wiki/Microcode |
My old instructor claimed that CPU vendors are highly secretive about their microcode, so you can't really know much at all about it for a specific CPU. Basically, you can say that machine instructions aren't really machine instructions, they're actually a high level language interpreted by Microcode, which translates it into actual processor specific instructions. This makes it easier to use the same standard machine code for a whole family of processors, yet still integrate new high performance features and tricks in newer devices, etc.
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