Opinions on cpu for FSX?

I am looking at specs for building a new system.

I am running FSX with low settings and a few scenery add-ons and aircraft. I would love to be able to add some traffic and/or weather with acceptable frame rates (25+). 95% of my flights are VFR in Cessna's.

As I understand it, FSX is CPU bound and will not take advantage of multi-core processors, and that CPU speed is paramount in performance, with RAM amount being secondary and video cards being tertiary in affecting performance. (Please correct if this is not true in your experience).

The new Intel Sandy bridge processors look like they may be great for price vs. performance. They seem to be very overclockable, thus helping the CPU issue.

I am looking at the 2600K right now. Any thoughts?
http://www.newegg.com/Product/Produc...82E16819115070

I believe FSX was patched to take more advantage of multi-core processors.

Core i7 quad core processors work great with FSX, and YES you can configure to use multi cores efficiently. Open up you FSX.cfg file and add this entry under the paragragh [JOBSCHEDULER]
Enter this:---------> AffinityMask=14

This tells FSX to utilise the last three cores (core 1 core 2 core3). Now most would ask, why not all four? Because Core 0 is bound to FIBERS and the main scheduler, which can not be unbound from that core, no matter how many cores you assign to FSX. That way core 0 is not tasked with anything other than the fibers. If you were to set AffinityMask=15,(all four cores) then core 0 would have the heaviest load, which will create stutters. Make sure you have HT disabled in your bios.

And go for I7 930 (cheapest on 1366), wich can be overclocked easily up to 4.0 Ghz with no problem (air cooled).

As vyper883 says, hyperthreading must be disable in your BIOS. FSX dont take any advantages of it.
Hyperthreading increases A LOT the CPU temperature and this is what you dont want to get it work at 4.0 (or even more) ghz. Of course, dont make any overclooking AFTER everything was running perfectly, and never during OS installation.

ASUS P6T and Gigabyte Ga-ex58-ud5 are the choices for motherboard.

Also you must read a lot over the web (including this forum) searching about Jesus Altuve (Bojote on avsim), UsePools=0, highmemfix=1, etc. to get the max on your I7 + great VGA in FSX conditions.

Thanks for the fantastic response.

VYPER883, so if you have 6 cores, you want to use 5 cores? The setting should be AffinityMask=16?

Matt Olieman

postedited

As far as I am aware, FSX only uses extra threads for texture pre-loading; all of the work to draw the screen including all windows, AI traffic, autogen etc is done on a single thread. I stand to be corrected, of course, but this is based on my reading of the information surrounding SP2.

That being the case you ideally want the CPU that can run a single thread the fastest. At the moment that would probably be the higher-end Sandy Bridge i7s. With Turbo Boost and (if you get an unlocked K model) multiplier control, you can get this to 4GHz or more on the busiest core with air cooling. With water, maybe 4.5GHz. That'd be several times as fast as the fastest computer available when FSX was released.

Going to be expensive, though. You need a new motherboard for Sandy Bridge (Socket 1155). Of the current crop, some of the Core i5 range will turbo boost a single core to nigh-on 4GHz.

The real problem for us these days is that the quoted clock speed of a CPU need not match what you'll actually see in use. With Turbo Boost and Speed Step, your true speed could be quite different. Case in point; I bought a new laptop recently which uses a Core i7 420 QM. This has a standard clock speed of 1.8GHz, which sounds a bit weedy (albeit a Core i7 does more per cycle than a Core 2 in many circumstances). But on mains power with Speed Step turned off, the busiest core will step right up to 2.93GHz, which means that it beats the pants off my other Core 2 tablet PC which runs at 2.6GHz natively.

I saw a mention on Wikipedia (thus, take with a large pinch of salt) that Intel had demonstrated a Sandy Bridge Core i7 K edition with the multiplier bumped up to 4.9GHz on air cooling. I'll believe that when I see it, but you should certainly be able to get well past 4GHz. Once the costs of the K edition come down a little I'll probably build one out and see how far you can push FSX on it.

Thanks for all of the input! Keep it coming.

If your current system is not based on Core i7, Sandy Bridge 2600k is the choice IMO. You'll be able to put the sliders almost to max without stutters, and the price for the whole setup MotherBoard+CPU+Memory will be similar than current Core i7 ones.
Jose

Quote:

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Originally Posted by Matt Olieman

... so if you have 6 cores, you want to use 5 cores? The setting should be AffinityMask=16?

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No. 16 is binary 10000 which means you are only using core 0 (which you can't stop) and core 4. To use the 5 other cores the binary is 111110, or hex 3E, or decimal 62. Each bit in the binary enables a core.

This assumes you have hyperthreading off in the BIOS. Otherwise there are 12 bits with every other bit being a pseudo-core.

Pete