Re: Patent on aligned memcpy

[joel at OARcorp dot com]

Jeez.... isn't an aligned memcpy obvious?  Surely there was prior existing
work to invalidate this patent.

Two things I notice technically:

1.  The wording uses the term compiler but the description sounds like an
interpreter since it is "implemented in a compiler that
compiles different portions of code at run time into a block of code
that is then immediately executed".  The words "immediately executed" are
what leads me to this thought.

2. Does this only apply to video memory?  Key phrase is in the last part:
"different color formats (bits per pixel)".

Regardless of its technical merit, it is a patent and looks like it could
be a problem subject to its interpretation.

--joel



On Wed, 19 Aug 1998, Mike Stump wrote:

> >From http://www.patents.ibm.com/details?patent_number=5706483:
> 
> ABSTRACT:
> 
> A method and apparatus for efficiently transferring a data block of
> bytes from a source to a destination in memory of a computer
> system. The method transfers bytes in multiple-byte words on
> word-aligned boundaries of memory as much as possible to reduce the
> number of fetches and writes and the number of memory cycles required
> to execute the transfer. For handling data block transfers of various
> sizes and locations, the method is implemented in a compiler that
> compiles different portions of code at run time into a block of code
> that is then immediately executed. The compiler employs a state
> machine stored in memory and having a plurality of states. Each state
> is associated with a portion of code for aligning a destination
> address or for transferring bytes in multiple-byte words on
> word-aligned boundaries. The states correspond to different starting
> source and destination addresses. A number of state machines are
> provided corresponding to the different color formats (bits per pixel)
> that may exists in the source and destination.
>