Re: Architectural implications of locate mode I/O and channels

According to Thomas Koenig  <tkoenig@netcologne.de>:

IBM patented the 709's channel: US Patent 3,812,475 filed in 1957 but
not granted until 1974. The patent is 488 pages long including 409
pages of figures, 130 columns of narrative text, and 91 claims.
>
https://patents.google.com/patent/US3812475A/en

But the sheer number of claims, 91, with around than half of them
indpendent (but quite a few formulated as "in combination", so there
may have been some dependency to other claims hidden in there...
must have taken the competition quite some time to figure out
what was actually covered, and if their own designs fell under
that patent or not.
>
And then it was granted after ~ 20 years, and continued to be
valid for another ~ 20 - US patent law used to be weird.

It is unusual for a patent to take that long without either the
inventor deliberately delaying it with endless amendments or it being
classified, neither of which seems relevant here.

You can't challenge other people for violating a patent until it's
issued, and by 1974 channels were rather old news. I never heard of
IBM enforcing it. They probably put it in the patent pool they cross
licensed to other computer makers.

"IBM's Early Computers" says almost nothing about channels other than
that they were invented for the 709 and added to the last version of
the 705.
--
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