Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site sdccs5.UUCP Path: utzoo!watmath!clyde!floyd!harpo!decvax!ittvax!dcdwest!sdcsvax!sdccs5!ee161agt From: ee161agt@sdccs5.UUCP Newsgroups: net.micro Subject: 4 -> 8 -> 8/16 -> 16 -> 16/32 -> 32 What next, 64 bit micros ? Message-ID: <1161@sdccs5.UUCP> Date: Mon, 12-Mar-84 21:02:27 EST Article-I.D.: sdccs5.1161 Posted: Mon Mar 12 21:02:27 1984 Date-Received: Wed, 14-Mar-84 19:07:39 EST Organization: U.C. San Diego, Computer Center Lines: 45 [] I have a crystal-ball study on my desk chock-full of predictions for the semiconductor industry in the next decade. Some of it I agree with. ( they predict 4M-bit Drams by 1992 ) Some of it I don't. In particular I wonder about this: "64 bits will be the common word-size of mP's by 1992." I'm not saying it's not technologically feasable to build a 64 bit Microprocessor; I'm wondering who would want or need one. Perhaps I'm short- sighted, but I can't see much performance or utility gain from a jump from 32 to 64 bits. 32 Data : 32 bits = 2 = 4,294,967,296 64 64 bits = 2 = 18,446,744,073,709,551,616 How many times do you use a number > 4 billion ? Is it reasonable to make data paths 8 bytes wide to allow for such rare cases ? I think you'd be better off doing this kind of math in double-precision. Floating point ? I don't do too much crunching, but I would expect 64 bits of double precision on a 32 bit machine would give you plenty of precision. Bus bandwidth: I'm all for decreasing the memory bottle-neck with a over-large memory bus, just don't increase the word size of the mP to do it. 64 data & 64 address pins ? That's 128 pins to start with without any multiplexing. I'd sure like to see those chips, they'd have pins sprouting from everywhere. Address : same as above. A 32 bit, 4 giga-byte virtual address space might get a bit small in the next decade, but is that any reason to go to 18,446,744 tera-bytes. ( don't even know prefixes above tera- ) How about 40 bit words or 48 bit words, anything but 64. I expect systems-on-a-chip long before 64 bit mP's. I'd prefer a cache, memory-management, I/O, even memory on the CPU chip before they start expanding the data & address paths. Any other views on micros beyond 32 bits ? Paul van de Graaf sdcsvax!sdccs5!ee161agt U. C. San Diego