amanda@mermaid.intercon.com (Amanda Walker) (02/17/90)
In article <10277@hoptoad.uucp>, tim@hoptoad.uucp (Tim Maroney) writes: > Do I get a choice of the boxed set or the Nintendo play-at-home version? Hey, you're a techno-dude; I figure you get the Nintendo version at least :-). > Thanks for the correction. Now, I just hope someone tells Steven Levy, > who wrote in the March 1990 MacWorld that "the mighty 68030 chip isn't > available in a CMOS version" (page 54). Well, I went back and checked. Motorola ads and so on say that the 68030 is implemented in HCMOS, which I interpreted as high-density CMOS. However, just to be sure, I just pulled my 68030 data book off the shelf and looked it up. Quoting from p. 1-3 (the capital letters were their idea, not mine :-)): "Implemented in Motorola's HCMOS Technology that allows CMOS and HMOS (High Density NMOS) Gates to be Gombined for Maximum Speed, Low Power, and Optimum Die Size" So I guess that when it comes down to it, we're both right (alert the media! Imminent death of the Net predicted!). However, I strongly guess that the HC prefix on the HC68000 means that it is built with the same process, and that the power savings are greater simply because there are many fewer gates on a 68000 than on a 68030. They might be able to drop the power my going to all high density CMOS, but the die size would increase, which could make for a yield problem. Maybe Motorola is waiting to get higher yields for smaller design rules before they go to all CMOS, or maybe it just doesn't make much difference. We're starting to get out of my league here; what we need now is a VLSI person from Motorola... -- Amanda Walker InterCon Systems Corporation "Many of the truths we cling to depend greatly upon our own point of view." --Obi-Wan Kenobi in "Return of the Jedi"
ehs@jumbo.dec.com (Ed Satterthwaite) (02/19/90)
In article <1990Feb16.195520.6853@intercon.com>, amanda@mermaid.intercon.com (Amanda Walker) writes: > > They might be able to drop the power my going to all high density CMOS, > but the die size would increase, which could make for a yield problem. Maybe > Motorola is waiting to get higher yields for smaller design rules before they > go to all CMOS, or maybe it just doesn't make much difference. We're > starting to get out of my league here; what we need now is a VLSI person > from Motorola... Well, in no way do I speak for Motorola, and I am a board designer, not a "VLSI person," but ... Most "CMOS" microprocessors are in fact fabricated from a mixture of CMOS and NMOS technology. Roughly speaking, a CMOS circuit requires more transistors than its NMOS equivalent, so that power consumption can be traded for die size within certain limits. Also, the power consumed by a CMOS circuit increases as the switching speed (clock frequency) increases. Thus the power advantage decreases as speed increases. Also, one can get hints about the dominant technology by looking to see if power dissipation is specified as a function of frequency. Here are some numbers pulled from Motorola's 680x0 data books. All are maxima and are functions of temperature, packaging option, etc., but the ratios should be about right: uP Pd (watts) 68000, 68010 1.5-1.7 68hc000 0.13 8 Mhz 0.19 12.5 MHz 0.26 16.7 MHz 68020 2.0 68030 2.6 Comments on the original query: For any given level of volume discount, the 68000 and 68hc000 are a *lot* cheaper than the 68030. But to take anything like full advantage of a 68030, including its 32-bit bus and higher clock speeds, a designer must pay a lot of other costs: twice as many bus buffers and transceivers, twice as many packages in minimum memory configurations (or expansion increments), perhaps a second-level cache built from high-speed SRAM, more expensive PC board technology, more cooling, etc. This gets expensive pretty quickly. IMHO, many of the existing 68030 (and 80386/80486) PC systems are catering to processor envy; the money would be better spent on upgrading the memory and i/o sytems than on the very latest, fastest CPU. Also, as I understand things, hw support for virtual memory will not be required for System 7 and, again IMHO, its use is a very bad idea on a Mac without a big, fast disk (maybe even then :>). Finally, in a related posting, Amanda Walker asks about the 68012. I believe that a recent issue of Motorola's Update announced the last chance for lifetime buys of this part. It's gone from the current price book. Ed Satterthwaite ehs@src.dec.com or {...}!decwrl!ehs