> > EISA is a pretty good bus, something like 6 times the bandwidth of ISA.
> > Isn't it completely upward compatible from ISA (i.e. we can use it just
> > like a ISA bus).
> No, it's completely incompatibel, from all 3 points of view:
> - connector (different pin spacing)
> - hardware (different signals)
> - software (probably, don't really know)
You need to tell that to my motherboard. ISA boards run just fine in EISA
slot connectors (I know, I do it). The pin spacing is different in the sense
that there are double the number of pins and they are spaced vertically one
above another. I don't know all the tech details, but ISA boards simply make
contact with only their required signals and do not interfere with the added
bus signals for EISA control.
> > I certainly wouldn't object to an EISA bus on the riscy board, and if
> > the ARC chips support it it's practically free.
> No, it wouldn't be free. The ARCset just has a few lines intended
> to be used to control the Intel EISA chipset.
> Again, quoted from the data sheets (uPD31432, page 107):
> 6.7 BUS SLAVE INTERFACES
> The uPD31432 supports two types of external bus masters: 386-type bus
> masters, and an EISA expansion bus interface based on the Intel 82350
> EISA chipset.
> [end of quoted material]
> That means that we can
> a) use the EISA bus (with all the advantages and disadvantages it has)
> b) skip the EISA bus and make our own ISA interface
> c) have no expansion bus at all.
> Ok, we already had a discussion wether we want an expansion bus
> or not and we decided to go with ISA.
> Assuming we have all the really necessary stuff on-board, I would
> go with EISA too. It would make the design faster again and it
> offers more speed.
> On the other hand, not one of the ISA cards people have would
> be useful.
WRONG AGAIN. ALL ISA boards should work just fine in an EISA bus system.
Again I'm doing just that (though obviously I have'nt used EVERY ISA board).
For example, in my EISA bus I currently have EISA AHA1742, ISA Hercules
Graphics Station video, and I had a DEC ISA Ethernet Card (I forget the
model) and a SONY CDU535 8-bit ISA bus interface CDROM drive. They
all worked just fine and cooperated without a hitch.
> ....... Specific design proposal omitted
Dan Fishman (firstname.lastname@example.org) (W) (303) 469-6469 (Fax) (303) 465-4396