Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!ucsd!sdd.hp.com!zaphod.mps.ohio-state.edu!rpi!raster From: raster@pawl.rpi.edu (Jerry D Bain) Newsgroups: comp.sys.ibm.pc.hardware Subject: Re: EISA vs. ISA Message-ID: Date: 14 Dec 90 03:37:07 GMT References: <51097@eerie.acsu.Buffalo.EDU> Distribution: usa Organization: Rensselaer Polytechnic Institute, Troy NY Lines: 33 Nntp-Posting-Host: pawl15.pawl.rpi.edu jc58+@andrew.cmu.edu (Johnny J. Chin) writes: >Excerpts From Captions of netnews.comp.sys.ibm.pc.hardware: >Sorry, but I think that you are wrong. EISA is not physically similar to ISA. >EISA looks like ISA, but the 32-bit section (pins) run in between the ISA pins >and are connected below the ISA pins. EISA pin connections are also narrower >than ISA. From my last comparison, ISA pins are twice as wide as EISA. Don't >ask me how, but the connections work. EISA slots are the same length as the >16-bit ISA slots. Actually, EISA slots have *two* layers of connectors. The first layer of contacts are ISA compatible. This makes the EISA bus ISA compatible. FULLY If a card wants to support the EISA extensions (32 bits, bus mastering), it has an extra set of gaps in the card-edge connector (like the single gap in a regular 16bit card) that allows it to reach all the way down into the second set of EISA control lines. This gives the EISA cards a funny look since they look like they have two rows of contacts. Inside an EISA board-connector though there are a matching set of doubled connectors for them. >MCA inferior to EISA? This is not what I've heard. I thought that MCA allows >for peripheral cards to talk to each other without CPU intervention. I'm not >sure that EISA can do this. Can it? The EISA standard can run at a much higher transfer rate than the MCA standard can. It supports all the functionality of the MCA bus without being tied the the IBM-proprietary patents. If memory serves, MCA runs at only 20mbit/s while EISA runs at 32mbit/s. EISA *does* support bus-mastering. There are many boards on the market already that fully support the EISA bus.