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

John Levine wrote:

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.

In general, IBM uses its patent portfolio in a defensive posture.
Imagine you are the employee of xyz corporation and want to assert
your newly granted patent onto IBM.
IBM will simply show you that they have 400,000 current patents that
they will assert back on you if you try. Most of the time, xyz corp
cannot afford to even read all of IBM's patents and remain with
positive cash flow. Often xuz corporation does not have enough
employees to read all IBM's patents in the duration their new
patent remains valid; and they certainly cannot afford to hire
lawyers to do it.

"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.