Path: utzoo!attcan!uunet!zephyr.ens.tek.com!gvgpsa!gold!grege From: grege@gold.GVG.TEK.COM (Greg Ebert) Newsgroups: comp.sys.ibm.pc.hardware Subject: Re: ISA boards, EISA bus Message-ID: <1471@gold.GVG.TEK.COM> Date: 20 Sep 90 16:53:01 GMT References: <1990Sep19.233544.16757@hayes.fai.alaska.edu> Organization: Grass Valley Group, Grass Valley, CA Lines: 60 In article <1990Sep19.233544.16757@hayes.fai.alaska.edu> fsdal1@acad3.fai.alaska.edu writes: >occasionally I see ads for EISA motherboards that sya they can use >either EISA or ISA boards. how can this be? >is this part of the EISA spec? > EISA is an upward-compatible backplane architecture which allows both ISA (standard PC and AT-bus cards) AND EISA cards to be used. It is impossible to put an EISA card into an ISA bus. The maximum tranfer rate is 33 MB/sec for 32 bit-wide transfers. [Damn, and I left my EISA spec with my previous employer..] There are 2 tiers of connector 'fingers' on an EISA card. _______________________________________________ / \ | | | Circuit board | | | | | | | \_______________________ ____/ |____________________| <---- ISA fingers |________________| <---- EISA fingers When you put an ISA card into an EISA slot, the physical width of the ISA bus connector area doesn't allow the card to reach the EISA signals. When you put an EISA card into an EISA slot, the card seats all they way down with ISA signals going to the ISA fingers, and EISA signals going to the EISA fingers. When you put an EISA card into an ISA connector, DUCK!!!! :-O Personally, I feel EISA is a crock of horse-puckey contrived to throw a monkey wrench into the PS/2 marketplace. So what if it's 32 bits. What on earth do you need it for ? For a variety of reasons, it's optimal to put RAM on the CPU board (if you have plug-in CPU's), or on the motherboard. What about disk controllers ? Sheesh, an AT bus-master can transfer about 4 MB/sec, which is 2-3 times faster than the fastest hard-disk transfer rate. Video, anyone ? Try caching video BIOS; now it's too fast - No joke, I'm totally serious. ETHERNET fizzles-out at 1.25 MB/sec. I don't think MODEMs will run that fast for awhile (sarcasm). I even heard it from the mouth of someone who personally attended the 'Gang of Nine' EISA meetings that it was definitely not the wave of the future. My advice is to put the money you would otherwise spend on a EISA system towards a 33Mhz 486, and a 'bus-master' type of hard disk controller (such as the Adaptec). ------------------------------------------------------------------------- ##### {uunet!tektronix!gold!grege} Register to vote, then ## | ## grege@gold.gvg.tek.com vote responsibly # | # # /|\ # Support the First Amendment, not the party that attacks it #/ | \# "I was, BANNED in the USA" - 2 Live Crew #######