PVUs and Processor Cores

[tcorum]

Ok I have a 550Q 8-way server. It shows 8 processors anyhow.

http://www-03.ibm.com/systems/p/hardware/entry/550q/index.html

The sales guy said that the server is actually 2 CPU Quad (4) core making it an 8-way server so I need to purchase 800 PVUs or 100 PVU per core. Then in a later conversation with an IBM Software Sales person they said that it is an 8-way server but the Power5 chip being duel core in most cases, that I would actually need 1600 PVUs. Can someone help me understand this? What is the real number of PVUs I need to purchase?

Thanks,

TCorum

 

[p5wizard]

Under AIX 5.3, power5 hardware can be run in SMT (Simultaneous Multi Threading) mode, where each core looks as though it is dual, because it has every register in duplicate, so it can quickly jump from one thread to another.

As you are on 5.2 still, SMT does not even come into play. so 8 CPUs: 800 PVUs.

BTW, even if it looks to the OS and APPs as though you have double the number of CPUs with SMT on, it is still an N-way and not a 2N-way.

The SMT on generally gives a CPU boost of 1.5 to 1.65, it doesn't really double the number of CPUs available.


HTH,

p5wizard

 

[hfaix]

550Q - has two CPU's (4 cores each) for a total of 8 cores. 800PVUs