*** Forwarded message, originally written by Ralph Schmidt on 15-Oct-97 ***

About the Jim Drew statement

The interrupt bug was fixed months ago and only occured with the
prototype board.  The bug report Email address was included with that
board, yet I never received any reports from Jim.

Other people who actually cared for the PowerUP development and
progress (and as such reported the bugs they found), regularly got
new versions of the ppc.library.


History of events with Jim Drew:

o In November 1996 he got a *free* board.
o In May/June we released a ppc.library so people could adapt to the
  new dynamic linking system.  This was an *ALPHA* version, and had
  several bugs, including the interrupt bug.
o Jim Drew starts to flame P5 on the Picasso96 mailinglist, saying
  that he fixed a bug in the PPC kernel.
o Wolf Dietrich mails him asking why he is flaming us behind our back,
  instead of sending bug reports...  which is what you'd expect from
  someone who got a free proto board.
o We recieve a ridiculous mail from Jim, saying that he tried contacting
  us by mail/phone/fax.  My Email address works fine and I never
  received anything from him... so I don't believe that he made any
  attempt at contacting P5 before Wolf Dietrich mailed him.
o Some weeks later he mailed Wolf Dietrich saying that he wanted 2-3
  CyberStormPPC boards in exchange for telling us what the problems
  were that he found.  Lots of problems have been fixed since the last
  ppc.library that he received, including the problems he found, we
  believe.


Imagine this:  You give someone a free prototype board which costs alot
of money.  Then you hear nothing from that person for months...  until
you notice that he is flaming you on a totally unrelated mailinglist.
And then the person asks for more free boards before he wants to tell
you the problem/bugs he found !!!



Regarding ppc.library:

The version released on the beta CDs was 44.29*BETA*, and *doesn't*
have the interrupt problem that the old alpha library had.
The non-beta library will be released soon.


- InvalidCache routine

  This routine doesn`t work as Jim Drew may think because an Invalid
  can`t work reliable with crossed cache line boundaries. And going
  down on cacheline boundaries would mean a lot "cinvl" loops which
  may mean a potential slowdown.  The reason for this routine was to
  offer a method to get rid of non dirty lines in the fastest possible
  way. It may get faster if I add some little checks for small data
  transfers and use cinvl... but that would mean a major slowdown for
  larger lengths.

  Currently, it does:

  if InvalidSize > 64kb do a cpusha
  if invalidaddress and invalidsize aren't aligned to 4k boundaries use
   1) CPUSHP on the first page
   2) CINVP all pages inbetween
   3) CPUSHP on the last page if that's still necessary.

  This routine wasn`t meant to do an Invalid Cache over the whole
  address space.
  1) This would only work for 16 byte aligned addresses and lengths.
  2) then you have to do max(4096/16) cinvl's for a not page aligned
     address in the first and last page of the address area.
     This may mean a lot overhead
  3) Inbetween you could then use CINVP for the pages...

  But this gets slower than CPUSHA very easily and that wasn`t the
  intention of this function.

  If he needs a perfect CacheInvalid function on line base and doesn`t
  care how long it takes he can send me an email.


- The PPCAllocMem not 32-bytes aligned problem Jim Drew observed.

  The old PPCAllocMem aligned to 32, but when I implemented the ability
  that allocs can be marked by the MMU, I needed to store the *ATTRIBUTE*
  of the memory allocation, so I know that I have to clean up the MMU
  stuff when the memory block is freed.
  The additional 4 byte offset is caused by the internal bookkeeping
  but the allocation itself is still 32 byte aligned so you don`t have
  to bother about this.
  I could align this again to a 32-byte boundary, but that would mean
  some additional memory waste.  Which is why I didn`t do it.
  If there`s a demand for an always 32 byte aligned memory ***address***,
  I can do that.


---
Ralph Schmidt,laire@popmail.owl.de(private),NextMail welcome
   Phase5    ,laire@ufoo.phase5.de(work),NextMail welcome
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