[Coco] Interesting thoughts on the HD6309

[Richard Atkinson]

I think the MOS Technology 6502 has this feature. Possibly Motorola
themselves could have implemented it in the 6809, but decided against it for
patent reasons?

Richard


On 2/4/07, jdaggett at gate.net <jdaggett at gate.net> wrote:
>
> Interesting find.
>
> Again as I was searching the patents on the US Patent Database, I cam
> across a
> Motorola Patent that also references other patents by RCA and Honeywell. I
> think
> I better understand  the reason the hidden feature of the 6309 when it
> does an
> instruction fetch while executing a previous instruction remained
> unpublished. It
> seems that Motorola did a patent on this feature but also there were 9
> previous
> patents on this same subject.
>
> Microprocessor having instruction fetch and execution overlap
>
> It more appears that Hitachi had implemented it in the 6309 and just
> before
> release of the product  info, their lawyers determined that any info about
> this
> mode would violate not just a Motorola patent but maybe also ones by RCA
> and
> Honeywell also. It is easier to fight one company in a patent infringement
> suit. To
> fight three or even four companies is far to difficult and costly.
>
> It looks as if Hitachi could not find a way around the ten patents and
> thus never
> deleted the feature. Instead they were silent about it and hoped no one
> would find
> out about it. By the time the community had found out about this
> feature,some of
> the original patents had expired and Motorola's was also near expiration.
> Also no
> one decided to persue infringement because Hitachi failed to document this
> feature and not use it as a selling point or an invention of their own.
>
> james
>
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