Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83 SMI; site sun.uucp Path: utzoo!linus!vaxine!wjh12!genrad!decvax!decwrl!sun!gnu From: gnu@sun.uucp (John Gilmore) Newsgroups: net.micro,net.micro.68k,net.arch Subject: Re: 68020 vs. 32032, pros and cons Message-ID: <1254@sun.uucp> Date: Tue, 12-Jun-84 04:00:28 EDT Article-I.D.: sun.1254 Posted: Tue Jun 12 04:00:28 1984 Date-Received: Thu, 14-Jun-84 06:37:07 EDT References: <452@trwspp.UUCP> <1048@vax2.fluke.UUCP> Organization: Sun Microsystems, Inc. Lines: 43 > National seems to have decided to do simpler components optimized to what they > consider to be the average use, rather than fancy parts that can be adjusted > to optimize your particular use. In exchange, national was able to produce > their parts, while motorola is still dreaming. Motorola's first parts were simple too, but they've been improving them over the years. (Over half of the 68000 microcode was rewritten for the 68010. Probably all of it is being done again for the 68020.) Nobody can dispute that the 16032's instruction set is seriously orthogonal, while the 68000 series only makes a half-hearted attempt. Nick Tredennick, who wrote the 68000 microcode, claims it's mostly his fault, because he couldn't make it all fit on the chip. The big Motorola win for me is performance. Motorola has shown that they can produce full-speed chips; we had a 16MHz 68000 sample close to two years ago, and many people run 12.5MHz production. People from National keep telling me that the 10MHz part is real, but somehow their customers keep mentioning 6MHz. Does a 6MHz 32032 outrun a 12.5MHz 68000? Also, I got the impression that the 32032 is not even close to twice as fast as the 16032 -- my correspondent seemed to think it ran roughly the same speed, since they didn't increase the internal processing speed even though they doubled the memory bandwidth. (68000-era processors and bus interfaces run at almost exactly the same speed, which means that just widening the bus would not speed them up much.) Motorola is speeding up the processor clock rate, the internal algorithms, the bus width, and the bus cycle time in clocks, while reducing the demand for bus accesses -- all by significant factors. I'll be glad to hear differently if National really did improve the guts of the 16032 to make the 32032 -- can anyone confirm or deny? > You will pay for that extra bit of performance through the nose though. OK, tell me the cost, don't just wave your hands. PS: If you want to build a co-processor of your own, don't try to hang it on a 32032; the CPU decodes the co-processor instructions, so you'll need a new CPU chip too, unless your co-processor instructions look a lot (well, OK, exactly) like their float box's. Motorola got it right. PPS: I'm pleased to see that unlike Intel, National is aggressively encouraging people to hook up their float chip to 68000 systems. Digital Acoustics is having great fun with them; they claim a 12.5MHz 68000 can keep two 16081's busy at once for serious numeric work.