Dual processors

[STRAT]

greetings

 

i was given this tip over at CGTalk. Dont know if it applies to all dual processors, but it certainly works for Xeons.

 

Press F8 during initial boot up to take you into the BIOS, then under the processor settings switch on the HT (hyper threading) option.

 

this will kinda fool the pc into thinking you have 4 chips instead of 2 and it utilises your 2 chips more officiantly.

 

you'll now have 4 render buckets instead of 2 with a render speed increase of up to 20%.

[quizzy]

There is an earlier post about this that you might want to take a look at too:

 

http://www.cgarchitect.com/ubb/ultimatebb.php?ubb=get_topic;f=2;t=000092

[Greg Hess]

1) This only works for Xeon's.

 

2) This only helps if your running Windows XP, or Windows 2000 Server.

 

If your running Windows 2000 SP2, and you enable hyperthreading, you'll get a sudden and massive performance decrease. This is because Win2k SP2 can't discriminate between a physical and a logical cpu, and upon seeing the first HT chip, marks both the physical and logical cpu's (Same primary processor) as the two cpu's towards its two cpu limitation.

 

(Thats why its disabled on almost all xeon's as shipped).

 

This was fixed in SP3, but it still counts the logical processors towards the 2 cpu limit, and will only allow usage of the two physical processors. (No Hyperthreading benefit).

 

Only Windows XP SP1 allows for full use of all processors in a Dual Xeon HT system. (Unless you wanna shell out cash for a server license).

 

Further Note: If you have a Dual Xeon system, its in your best BENEFIT to upgrade to a bucket based renderer ASAP. Bucket renderers, like vray/brazil allow for the logical processors to be assigned individual buckets, fully utilizing intel's hyperthreading abilities. (Aka you see 4 buckets when u render).

 

Max5's default radosity and scanline engine by comparison, gains only a 6-8% benefit from a dual non HT xeon, to a Dual HT Xeon....vray sees upwards of 25%.

[STRAT]

cheers for the info Greg.

 

i run a Xeon using winXP, and it's difficult to gauge the speed increase ratio using a standard scan line renderer because it stays using a single scan line.

 

luckely my beloved C4D R8.1 utilises HT

[Greg Hess]

Hey Strat,

 

If your using Max5, make sure to click SSE on as well. Its disabled in the render dialog by default for some stupid reason. Enabling it has the same effects as the Max 4.26 patch, adding some of intel's optimizations to the default scanline renderer...gives a decent boost to P4's/Xeon's, a rather minor boost to athlon XP/MP and Pentium 3's.

[Richie]

Hello

 

@Greg

 

This is exatly what I'm talking about before in an earlier thread (you maybe remember).

HT on Win2K.

 

Richie

[Greg Hess]

Aye,

 

So you can either be a fruitcake, and not upgrade your os, losing a possible performance advantage...or spend 120 dollars and upgrade your os.