Xref: utzoo comp.arch:6875 comp.sys.next:340 Path: utzoo!yunexus!geac!syntron!jtsv16!uunet!seismo!sundc!pitstop!sun!decwrl!pyramid!oracle!hqpyr1!csimmons From: csimmons@hqpyr1.oracle.UUCP (Charles Simmons) Newsgroups: comp.arch,comp.sys.next Subject: Re: RISC v. CISC (really comments on many postings: LONG) Message-ID: <468@oracle.UUCP> Date: 26 Oct 88 08:18:47 GMT Article-I.D.: oracle.468 References: <156@gloom.UUCP> <6865@winchester.mips.COM> Sender: news@oracle.uucp Reply-To: csimmons@oracle.UUCP (Charles Simmons) Organization: Oracle Corporation, Belmont CA Lines: 75 In article <6865@winchester.mips.COM> mash@winchester.UUCP (John Mashey) writes: >As you note, not-yet-announced. On the other hand, MIPS R3000s >do 42K Dhrystones, and they're already in real machines, and vendors >are quoting the CPUs at $10/mip, i.e., $200 for 25MHz parts. >Starting from scratch in 1984, and getting the first systems in mid-1986, >the high-performance VLSI RISC [i.e., MIPS as example] is: > 1986 5 MIPS > 1987 10 MIPS > 1988 20 MIPS The above two paragraphs aren't here for any good reason. I just liked them. (Remember that an Amdahl 5890 [the second fastest scaler processor in the world...:-] does on the order of 42 or 43K dhrystones.) >>From: doug@edge.UUCP (Doug Pardee) >>The incorrect assumption here is that you would want to build a mainframe >>using RISC technology -- that RISC technology has anything to offer at >>that price/cost level. >Well, M/2000s act like 5860s, and we think next year's M/xxxx will >make 5990s sweat some. Why wouldn't we want to build RISC-based mainframes? >Lots of people do. A couple things. At Amdahl, people do think about things like building a RISC based mainframe processor. The big problem that arises is in guaranteeing object-code compatibility for old COBOL binaries that do ugly things like use self-modifying code. But mainframe people are definitely interested in RISC technology, and are working on thinking up ways to take advantage of the technology. John Mashey brings up a point that I've never had a satisfactory answer to. If we assume that RISC-based manufacturers can build machines that outperform mainframes, where will companies like Amdahl make their money? When I asked this question around Amdahl, the answer was "I/O bandwidth. I/O bandwidth!" To what extent would next year's M/xxxx (40 Mips?) processor really make a 5990 sweat? I'll concede that on some programs, this processor- to-come will be as fast as a 5990. But let's look at the kinds of processing that are common on mainframes: database processing. A 5990 can be equipped with 256 Megabytes of 55nanosecond static ram. (That's its main memory, not its cache.) That kind of memory costs a whole lot, and if you need that kind of memory (for your huge database and 3000 users), it's going to cost, even on a RISC based mainframe. The 5990 also has lots of I/O bandwidth. (Anyone want to help me with the numbers here?) I believe that you can hook up something like 32 4.5Megabyte (byte, not bit) per second channels to one of these beasties. That kind of I/O bandwidth costs. (For comparison, a diskless Sun has about 1.25 Megabytes of bandwidth [10 Megabit Ethernet].) A diskful Sun probably doesn't have much more than 4 Megabytes. So, a mainframe can do something like 30 times as much I/O as a workstation...) (People at Amdahl would also mention that when you build a mainframe, is has to be highly reliable and extremely serviceable. Apparently, there's a fair amount of hardware and money that go into increasing the reliability and serviceability of a mainframe.) So, the basic claim that I want to make, and that I'd like to hear counter-arguments to, is that if you build a RISC-based mainframe, it's still going to cost $10,000,000. (Random thoughts... People at Amdahl are starting to worry that the next generation of Amdahl mainframes might be able to support 64K concurrent processes, or at least enough processes to make pid's wrap way to frequently. Has MIPS started worrying about the problem of 16-bit pid's yet? Seems like MIPS might run into trouble in 1990 or 1991...) (16-bit major/minor device numbers are already too small for a 5890 [have you ever tried to configure 3000 terminal devices in an 8-bit field?] How much trouble is MIPS having with this 16-bit limit?) -- Chuck