Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!van-bc!ubc-cs!alberta!cpsc.ucalgary.ca!ctycal!ingoldsb From: ingoldsb@ctycal.UUCP (Terry Ingoldsby) Newsgroups: comp.arch Subject: Re: Will NeXT survive? Grow with the times? Summary: Overlooked feature of RISC Keywords: More questions on RISC vs. CISC Message-ID: <658@ctycal.UUCP> Date: 24 May 91 23:16:28 GMT References: <11399@uwm.edu> <2050@kuling.UUCP> Organization: The City of Calgary, Ab Lines: 31 In article <2050@kuling.UUCP>, rolande@kuling.UUCP (Roland Eriksson) writes: ... > IMHO the main advantage that RISC arcitechtures has over CISC > is that register operations are faster than memory operations > and that the compiler writer do not know good ways to use the > more complex ones of the instructions of a CISC processor. This > is NOW. Whe have "only" about 1 miljon transistors in the most > complex processors today (RISC or CISC). But we will soon have > fabrication techniques to produce chips with 10 miljon transistors. Debating RISC vs CISC on this basis misses one of the most important factors governing RISC/CISC performance. One of the original features of RISC technology was the speed with which a design could be created and implemented. Since the implementation technology has to be frozen at some point in the design cycle (I presume fairly early on) this means that performance of the implementation is inversely proportional to the time it took to produce it. CISC machines take longer than RISC machines, so currently available CISC chips necessarily use older technology. At present, hardware improves at a dizzying pace. This means that RISC chips have an inherent advantage. Unfortunately exponential growth never continues indefinitely. Eventually RISC will lose the implementation advantage over CISC. At that point, my guess is that architectures will end up sort of in the middle; i.e. more features than RISC, less than current CISC. -- Terry Ingoldsby ingoldsb%ctycal@cpsc.ucalgary.ca Land Information Services or The City of Calgary ...{alberta,ubc-cs,utai}!calgary!ctycal!ingoldsb