🚀 go-pugleaf

In article <79@mtxinu.UUCP>, ed@mtxinu.UUCP (Ed Gould) writes:
> >> I hate to tell you folks, but Andy Bechtolsheim here at Sun has a patent 
> >> (applied for and granted) on using the untranslated addresses as the 
> >> RAS addresses and doing the MMU address translation before the column 
> >> addresses are needed for CAS.
> >
> >How the hell can the patent office grant patents like this?  It's sort
> >of like patenting the idea of grounding DTACK on a 68000 or putting
> >chocolate ice cream in root beer; the idea is too obvious.  To coin a
> >phrase, it's patently ridiculous.
> 
> If it's so obvious, why didn't anyone think of it before Andy did?

Let's look at this for a minute.  You have the following problem:

) you want virtual to physical address mapping
) standard practice is to map only the high order bits
    (this predates Andy by a good long time)
) virtual to physical mapping takes some time
) you want to use dynamic rams
) dynamic rams require half of the address, and then, some
    delay later, the other half
) Gee, Wally, what do we do now?

It's not that nobody thought of it before, but nobody patented it.
It's not a clever idea; it's the only reasonable solution.
I had a design like this for the 6809 and dynamic memory before the
68000 even came out; I just never built it.

It bothers me that such ideas can be patentable.  When you design
a new machine, these patents can restrict your design space; if they
start patenting all the good solutions to common problems, what do
we have left to design with?

-tom