Replacing PA-8800 CPUs with PA-8900

[Alex Georgiev]

So, it appears that the software developers have finally figured out how to bog down 6 dual-core PA-8800 CPUs (12 cores).

Since my run queue lengths (HP-UX) are not very high (less than 3 at 100% utilization during peak times) I'm more inclined to go with faster CPUs rather than add more CPUs.

I'm currently running 1 Ghz PA-8800 CPUs. Changing to Itanium is not an option because it will take time... The only thing I can do is go to PA-8900 1.1 Ghz CPUs.

My questions are:

1) Will I need to buy LTUs (license to use) for HP-UX? I am just replacing CPUs after all, not adding.

2) Should I be worried about any overheating?

3) The system is an rp8420 with two cells. Do I need to do anything to adjust the clock frequency?

4) Anything I should watch out for?

P.S. HP CE will be doing the replacement, of course, not me. I'm just trying to do my homework.

Many thanks in advance!

[Dennis Handly]

Are you sure you are bogged down with the CPU vs I/O or memory? Have you used glance to determine this?
Are your developers using lots of threads?

[Alex Georgiev]

I'm positive! I've been looking at Glance & MeasureWare stats.

The developers are actually in a different company... :-) It's a large ISV.

[Duncan Edmonstone]

Alex,

1) Will I need to buy LTUs (license to use) for HP-UX? I am just replacing CPUs after all, not adding.

- No you won't.

2) Should I be worried about any overheating?

- No

3) The system is an rp8420 with two cells. Do I need to do anything to adjust the clock frequency?

- No - the CE should take care of anything like that - he might do a firmware upgrade as well.

4) Anything I should watch out for?

- not really - I'd probably look to bring yourself up-to-date on patches prior to the upgrade though - apply the latest quality pack...

what sort of improvement are you expecting when going to PA8900 - I'd be surprised if you saw a lot more than 10%

HTH

Duncan

[Bill Hassell]

As Duncan says, faster CPUs are just not that much faster. There are a number of internal chip features that can improve some operations but not nearly as much as an additional CPU or two, assuming that uptime reports a lot more than 1.00 workload. The 8900 will run each instruction a bit faster, but another CPU or two will run in parallel and overall performance will go up quite meaningfully.

The only downside might by increased licensing costs for CPU-count license methods.