Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!ucsd!sdd.hp.com!hp-pcd!hpfcso!rjn
From: rjn@hpfcso.HP.COM (Bob Niland)
Newsgroups: comp.sys.hp
Subject: Re: HP 9000/400 question
Message-ID: <7370192@hpfcso.HP.COM>
Date: 10 Aug 90 18:46:16 GMT
References: <j902s89@Unify.Com>
Organization: Hewlett-Packard/FSY Ft.Collins,CO,USA
Lines: 26

re: >> Your self-modifying code for your 300 will work fine on your 400, (but
    >> will break on both 300 & 400 when you upgrade to 68040 with copyback
    >> cache enabled :-)

> This is actually no laughing matter.
> If the data updates are not seen by the I-cache, the system will not work.

We know it.  My remarks were partially intended to get end users and
software developers thinking about the issue.

> Hopefully there will be some system call in future versions of HP-UX to
> flush the complete cache system back to memory (and invalidate I-cache
> entries).

There will, and in the '040 release (be that 7.05 or 8.0).

> I hope HP doesn't shoot itself on the foot on this one.

The default will be that copyback is enabled, with 'chatr(1)' options and
other methods to disable/flush it in stages.  I don't have the complete
details, but I do know that providing cache controls for the user is a hot
topic in the software lab.

Regards,                                              Hewlett-Packard
Bob Niland      Internet: rjn@hpfcrjn.FC.HP.COM       3404 East Harmony Road
                UUCP: [hplabs|hpfcse]!hpfcrjn!rjn     Ft Collins CO 80525-9599