HP 3000 Manuals

COMMUNICATOR 3000 MPE/iX Release 5.0 (Core Software Release X.50.20)

Introducing Memory Page Deallocation (MPD) 

Steve Flynn 
Systems Technology Division 

Remember the old days when the detection of bad memory would cause a
system failure on the HP 3000?  Remember when a CE had to come on site to
replace the whole board before you could get the system back up?

Increase of system and memory sizes and continued customer demands for
higher system availability has lead to the implementation of Memory Page
Deallocation (MPD).

With the first Corporate Business System (990,992), Hewlett-Packard
introduced Memory Bank Deallocation.  This was the dynamic deallocation
of a memory bank (64 Megabytes).  If the system detected a failure in
memory, it would cause a system failure.  The system would then reboot
and automatically deallocate the bank that contained the memory failure.
Scheduled system downtime would be required and the CE would come on site
and replace the defective memory module.

With the introduction of the HP 3000 Corporate Business Systems (991,995)
and MPE/iX 5.0, Memory Page Deallocation(MPD) has been implemented.  The
concept behind MPD is to simply remove or deallocate the page with the
offending problem, thus making it unavailable for system use, rather than
taking down an entire 64-Megabyte bank (and eventually replacing the
memory module).

With MPD, the system proactively searches online for bad memory locations
and corrects them.  If the system software cannot correct the bad memory
location, the memory page (4 Kilobytes) will be deallocated to prevent a
potential system failure, thus increasing system availability.  For more
information, please refer to the technical article "Memory Page
Deallocation (MPD)" in this Communicator.

MPE/iX Communicators