08-27-2007 02:48 AM
In the world of HP-UX, IA usually inidicates IA64 while PA usually denotes PA-RISC - two different CPU architectures.
IA64 is an EPIC CPU architecture, whereas PA-RISC is a RISC CPU architecture. Wikipedia does a reasonable job of explaining the difference:
RISC - http://en.wikipedia.org/wiki/Risc
EPIC - http://en.wikipedia.org/wiki/Explicitly_Parallel_I
As far as HP-UX is concerned, PA is the past and IA is the future - without knowing specifically what you want to compare its difficult to explain in more detail than that.
08-27-2007 02:53 AM
Some of the "gotcha's" includes PA_RISC legacy code that has not been ported (and never will be) to IA. The Aries emulator goes a long way toward satisfying that request although there will be a performance hit on that portion of the code that is CPU-bound. Even in those cases, the IA hardware may be so much faster than the older PA-RISC hardware that the performance impact may be negligible.
This is really one of those pay-me-now or pay-me-later situations because eventually PA-RISC will be obsolete. The only cases where I would not recommend IA these days are extremely computationally intensive applications which have not been ported to IA.
08-27-2007 03:14 AM
PA-RISC systems are using HP-PA CPUs (e.g. HP PA-8900), Integrity systems are using Intels Itanium 2 chip (e.g. Montecito or Tukwila in the future).
On some servers (e.g. rp4440 and rx4640) this is the only difference (together with an appropriate firmware).
Of course a different CPU needs different code to work. HP-UX 11i v2 and v3 has the bits optimized either for PA-RISC or Itanium (both on the same DVD set).
Hope this helps!
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08-27-2007 03:36 AM
The primary business issue is that HP has pulled the plug on PA-RISC and stopped development.
They have cut prices on Itanium and pushed it hard. The boxes can run Windows or Linux in addition to HP-UX.
It's tough to justify bucks, especially big bucks on PA-RISC, a dead end platform.
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08-27-2007 05:00 AM
My guess if that RISC hardware will be around long enough for all software and software manufacturers to get used to that idea and certify their products and then we will really see it start declining.
I have advised all my clients, if they want to stay with HP hardware to start moving away from RISC hardware and start adopting Itanium hardware, if their software will support it. If their software isn't supported then just go with a hardware upgrade if it's cheaper than buying a new server (sometimes it is). This will give their software company more time and keep their hardware more current.