From: mccall@mksol.dseg.ti.com (fred j mccall 575-3539)
Subject: Re: Bus def's ==> Re: EISA vs. ISA (& VESA, VL-bus, Local bus)
Organization: Texas Instruments Inc
Date: Wed, 16 Dec 1992 00:08:24 GMT

In <8738@lhdsy1.lahabra.chevron.com> hwrvo@kato.lahabra.chevron.com (W.R. Volz) writes:

>In article <1992Dec11.203408.10688@mksol.dseg.ti.com>, mccall@mksol.dseg.ti.com (fred j mccall 575-3539) writes:
>|> In <8673@lhdsy1.lahabra.chevron.com> hwrvo@kato.lahabra.chevron.com (W.R. Volz) writes:
>|> 
>|> >|> While we are at the subject, could some one please tell us all,
>|> >|> what are the differences between 
>|> >|> 	* ISA         (the mormal 386 type bus, right?)
>|> >|> 	* EISA        (extended ISA, 32 bit, look like IAS but twice
>|> >|>                        longer right?)
>|> >|> 	* VL-bus      (differnt type of expansion slot, looks all
>|> >|>                        diferent, much smaller than ISA, connected to the
>|> >|>                        CPU directly, good for video cards, or is it VESA?)
>|> >|> 	* Local Bus   (?)
>|> >|> 	* VESA        (?^10)
>|> 
>|> >EISA is a new Extended ISA bus. It is 32 bits wide and runs at 33 mhz, 
>|> >I think. This bus should be 32 * 33 / ( 16 * 8) or about 8 times faster
>|> >than the ISA bus. I don't know what cards are available but ISA is 
>|> >compatible with this bus though is halves the bus speed. Don't know what
>|> >that does to cards expecting an 8 Mhz bus.
>|> 
>|> People keep asking this question, and people keep getting it wrong.
>|> EISA runs at ***8.33*** MHz.  It will transfer at FOUR times the speed
>|> 

>It appears that, usually, when someone asks a reasonable question, he
>gets no responses. I've asked several and got little or nothing in return.
>The most is usually a few asking me to send on replies if I get them.
>I found that I can learn much more by answering a question, even if
>I know the answer is wrong. I know that someone will correct me and I
>can take the median of the answers and the true answer. 

But what about people who get screwed up by the wrong answers?
They've heard a bunch of answers and don't know which one is true
anymore, because people were giving wrong answers authoritatively.

>Try calling
>several vendors and ask them the same question and see if you get the
>same answer. I've been corrected on this twice now so the EISA bus
>speed seems to be 8.33 mhz. 

I *HAVE* one.  If it isn't 8.33 MHz, it does not match the EISA
specification.  If you find a vendor giving you wrong answers, all I
can suggest is not doing business with that vendor and spread that
news around so other people won't, either.

>As for local bus at 50 Mhz, there still 
>seems to be questions if the bus can still be called VESA. It doesn't
>really matter. 

Well, it does to the point where it can't call itself VESA unless
they are ready for the lawsuit.  The VESA spec won't let you go that
fast.

[This I don't have one of, so this one is hearsay.  But I suspect it's
correct, since vendors have told me this.]

>For those who took the time to correct me, thank you. I've learned
>something and will be able to ask more intelligent questions when
>I go and buy a system this weekend. 

>I still have questions on EISA vs ISA, local bus or not. I won't ask
>them here, because after today it'll be too late to change. 
>Unless they have a 30 day money back guarantee.

It still depends on what you're going to be running and what you plan
on doing with the system.

-- 
"Insisting on perfect safety is for people who don't have the balls to live
 in the real world."   -- Mary Shafer, NASA Ames Dryden
------------------------------------------------------------------------------
Fred.McCall@dseg.ti.com - I don't speak for others and they don't speak for me.