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Posted by Jay G. on 06/07/06 11:58
On Tue, 06 Jun 2006 05:28:29 GMT, Roy L. Fuchs wrote:
> On Mon, 5 Jun 2006 20:52:23 -0500, "Jay G." <Jay@tmbg.org> Gave us:
>
>>"IBM decided to make the MCA bus proprietary. It in fact did this with
>> ISA as well..."
>
> IBM didn't charge peripheral device makers a fee for designing with
> the ISA bus, however.
You sure about that?
http://www.walshcomptech.com/ps2/ncr3300.htm
"the MCA bus cost more to license than did the ISA bus"
Granted, most sites don't mention a licensing fee for ISA, but most sites
don't mention licensing particulars for many different devices.
I did find some other interesting tidbits about ISA licensing though, in
regards to MCA:
http://www.skynet.ie/~stephen/buses.html
"This licensing fee including a retroactive fee for the use of the
ISA bus technology. "
http://www.firingsquad.com/guides/hiwdisplay/page7.asp
"Before IBM would be willing to license the MCA bus, they also required
that vendors pay a retroactive royalty for the use of the ISA bus as
well.
So IBM wasn't altruistic, and did charge licensing fees for ISA when they
could, as they could when licensing MCA out.
Also, there's these interesting quotes about how the ISA "standard" came
about:
http://www.computerhope.com/help/bus.htm
"Introduced by IBM, ISA or Industry Standard Architecture was
originally an 8-bit bus that was later expanded to a 16-bit bus
in 1984."
http://www.quatech.com/support/comm-over-isa.php
"However, it was officially recognized as "ISA" in 1987 when the IEEE
(Institute of Electrical and Electronics Engineers) formally documented
standards governing its 16-bit implementation."
So how could a format that came out in 1984 not have a "standard" until
1987, 3 years later? Surely IBM had a standard that they used for all
their systems.
The answer seems to be in this last quote:
http://users.ece.gatech.edu/~hamblen/489X/ISA.htm
"The "AT bus", as IBM originally called it, was first documented in an
IBM publication called the PC-AT Technical Reference. The Technical
Reference included schematics and BIOS listings that made it easy for
other companies like Compaq to produce IBM compatible clones. The
companies producing IBM compatibles could not use the "AT bus" name
however since IBM had protected it with a trademark. In response, the
industry coined "ISA" as a new name for the bus that was eventually
adopted by everyone including IBM.
Although the PC-AT Technical Reference included detailed schematics and
BIOS listings, it did not include the rigorous timings, rules, and other
requirements that would make it a good bus specification. As a result,
the various implementations of ISA were not always compatible with each
other."
So it looks like the AT bus was a proprietary device of IBM, like the BIOS
originally was. However, like the BIOS, clone manufacturers were able to
reverse-engineer the AT bus and create their own versions of it. However,
since they didn't have the entire specs for the bus, and possibly couldn't
use the exact specs IBM used even if they had them, different
implementations of the bus were used until the ISA standard was made.
Granted, this is pieced together from the various sources I've read, but it
seems clear that ISA became a standard *despite* being proprietary, not
because it wasn't.
Also, it should be pointed out *again* that many proprietary formats that
are charged licensing fees become the de facto standard, such as CD, DVD,
and mp3. HD DVD is also proprietary and has fees attached, and as such is
no different in that regard than Blu-Ray.
Other links about ISA:
http://www.iotech.com/ee9712.html
http://www.ackadia.com/computer/system-architecture/system-architecture-buses.php
-Jay
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