My PC was recently having some difficulties which were narrowed down to a failing SSD – after 4 years I’d be pretty tired too, so I wasn’t too aggrieved that I’d need to replace it. While I was at it, I upgraded a few other components too:
- CPU from an E8400 Core2 Duo @ 3GHz to a Core i5-2400 @ 3.1GHz (with two extra cores)
- 8GB Ballistix DDR2 800MHz (they make memory that slow?!) to 32GB Vengeance 1600MHz
- 1x 64GB Kingston V+ SSD (220MB/s out, 140MB/s in) to 2x 120GB Agility 3 SSDs (525MB/s out, 500MB/s in)
Problem is – the new system was substantially slower than the old one. Initially I thought that was down to having had the two SSDs RAID-0’d and the chipset not liking it, so I broke the array and reinstalled to find things marginally improved but still slow. In fact, the wheels were coming off the wagon with the Anytime Upgrade to W7 Ultimate, with long pauses on startup and sluggishness in games.
Some Googling later and I found a Stack Overflow post detailing a suggested fix – bizzarely, to turn on the integrated graphics on the motherboard (even though I’ve a PCI-E graphics card) and allocate to it as much RAM as the BIOS will allow (480MB ish).
Proof’s in the pictures:
What the shit?
Most likely this is because the onboard GPU for your machine is on the same die as the CPU (http://images.anandtech.com/reviews/cpu/intel/sandybridge/review/die.jpg), thus the data speeds between the CPU cores and the GPU are huge. That will always have a massive advantage over your usual GPU (which is accessed via the PCI bus), so it’s not a bad idea to have both switched on and let the system use the onboard GPU for floating point calcs, while using your GPU for rendering.
Also, your DIMM configuration can have an impact. With Intel CPUs, if you populate too many channels of memory the overall memory bus speed will drop. You usually only see this on the Xeon range when it’s common to find motherboards with 3x channels. Try playing with your RAM config, and using CPU-Z to see what speeds it is actually running at.
I suspect it’s a chipset bug – note that I’m not actually using the onboard graphics, it just needs to be turned on for the slowdown to go away. Crucically it makes no apparent difference whether the on-board GFX is turned on or not when less than 32GB of RAM is installed.
There’s a ticket open with Gigabyte to see what the score is…