Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1+some 2/3/84; site dual.UUCP Path: utzoo!linus!philabs!cmcl2!seismo!ut-sally!mordor!dual!paul From: paul@dual.UUCP (Baker) Newsgroups: net.arch Subject: Re: "When to go to CMOS", or, "Is Schottky dead" Message-ID: <836@dual.UUCP> Date: Thu, 11-Oct-84 12:13:05 EDT Article-I.D.: dual.836 Posted: Thu Oct 11 12:13:05 1984 Date-Received: Sat, 13-Oct-84 01:11:59 EDT References: <537@turtlevax.UUCP> Distribution: net Organization: Dual Systems, Berkeley, CA Lines: 57 > Myriad new high-speed CMOS IC's are coming out from lots of new > startups as well as some of the old fogies. AMD, Analog Devices, > Cypress, Integrated Device Technology (IDT), International Microcrcuits > (IMI), Lattice, Logic Devices, TRW all have LSI devices (memories, > processing units), pending or available. Other companies, such as > National, TI, Zytrex, RCA, have got high-speed CMOS MSI chips > (registers, gates, decoders, etc.). Most of these high-speed CMOS circuits appearing seem to be about half the speed of LS parts. It is is a bit hard to tell as many of the CMOS manufacturers only publish "typical" specifications. These are quite useless for design purposes as you are not guaranteed to only get "typical" parts. They do appear to be quite useful for slow speed parts of circuits which are not connected to external buses, where it is desirable to conserve power. In looking at retrofitting some of my existing designs, it is surprising just how few parts are candidates for this. Zytrex did have a lot of double page advertisements headed "Who killed Schottky dead?", with, as usual, no indication of the parts they produced. After many further enquiries, it turns out there are supposed to be two speed selections, one about as fast as LS the other about as fast as S. The second are completely unavailable and I'm still waiting for samples of some the first types. > It almost seems like it is near the time when a design may consist > entirely of CMOS components. Not for a few years yet I think. Where CMOS will do very well is in the area of gate arrays and other large scale circuits. It appears that most of the slowness of the current high-speed CMOS is in the output buffers. Also the range of parts available in high-speed CMOS is very much smaller than for LS or S or even F series of TTL. This is particularly noticeable if attempts are made to get parts. At the moment many 20 pin, 8 bit parts are available (HCT373, HCT244, etc). I believe HCT00s and simple parts are also available, but you do not reduce power consumption much with these as the simple LS parts do not consume much anyway. I am still having trouble getting samples of HCT174s and HCT393s - not exactly high-tech but not exactly available either. > How close is high-speed CMOS to price parity with S or LS? Some of the > components (MSI) are dominated by packaging costs, so should be no more > than 5% more expensive than their bipolar counterparts. How about LSI > components? Nearly all parts costs are dominated by "what the market will bear" rather than by any real costs of manufacture. At the the moment high-speed, or as I call them High-Cost, family of CMOS parts seem to cost about three times the equivalent LS parts, sometimes more. For example a 74LS670 has a cost of about 70 cents. I was quoted about $5.00 for a CMOS TTL compatible version. Another thing to consider is that many of the less common parts are only made by one manufacturer, sometimes a rather obscure one. Purchasing departments tend to give engineers a hard time about specifying parts like this. Paul Wilcox-Baker.