On Saturday, August 5, 2023 at 1:48:38 AM UTC+9, Amine Moulay Ramdane wrote:
> Hello,
> More of my philosophy about CISC and RISC instructions..
> So we can generally consider CISC (Complex Instruction Set Computer)
> instructions of x86 architecture to be higher-level programming instructions compared to RISC (Reduced Instruction Set Computer) instructions due to their complexity.
>
> CISC instructions are designed to perform more complex operations in a single instruction. This complexity allows higher-level programming languages and compilers to generate fewer instructions to accomplish certain tasks. CISC architectures often have a broader range of instructions, some of which might even directly correspond to operations in high-level programming languages.
> In contrast, RISC instructions are designed to be simpler and more streamlined, typically performing basic operations that can be executed in a single clock cycle. It might require more instructions to accomplish the same high-level task that a CISC instruction could handle in a single operation.

CISC vs. RISC was disucussion in 80s, you can find discussion between RISC-I designer (now Esperanto Tech’s CEO) and Vax designer through IEEE transactions.

I think that it is no longer better point of view, becase;
1)Hardware design tools are advanced,
-it supports design of complex architecture and logic circuit with reasonable performance,
-it supports analysis of complex design.

2)Semiconductor process node are advanced,
-it supports enough transistor counts and realizes complex design,
-it supports lesser fabrication cost for old processes (28nm or less have best cost/performance),

3)Needs is changed,
-Application/domain-specifc architectures are rised,
-Every domain requires different specifications.

4)Logic circuit design philosophy is separated from architecture design philosophy now,
-Logic circuit should be simpler (mainly for verification cost and integration density), this is same from ancient (not only computers).
-But architecture(or mechanisms for processing) can be complex(first two reasons).

-
S. Takano

ps.
tired of social network services, so back to here :)

> Thank you,
> Amine Moulay Ramdane.