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2011 Macbook Air i5 slower than old 2010 C2D

D

drvelocity

macrumors regular
Original poster
Oct 20, 2008
119
94
I've got a i5 1.7 13" Macbook air with 4GB/256GB that has always seemed slower than my old C2D 13" from last year. I finally ran Geek Bench and XBench on this machine and found that indeed both are benchmarking much slower than they should. I get 1800-2000 on Geekbench when most i5's are getting 5500-6000, and even my old machine tests at 3000. Xbench is similarly low. I've made sure that no other programs are running from the user or system, so that's not the issue. The computer always runs cool and the fans never kick on.. the CPU speed is reported by miniStat as 1.7Ghz. Any ideas?

The weird thing is on the Geekbench browser site maybe 5% of the results are similarly low - 1800. The rest are all in the 5000+ range. My memory speeds on Xbench were low as well, but the SSD speeds are normal. Is this some kind of serious bug affecting a minority of machines? Some kind of really overzealous CPU throttling?
 
sounds like a problem in the testing procedure.

I dont know geekbench or exactly how it tests, but the sandy bridge i5s' used in the new AIR's are ULV's processors.

1.7ghz is the default low mode. which it runs on while not under strain, but all of them 'overclock' so to speak and ramp up the power under load and when necessary.

I believe the i5 shoudl ramp up to 2.3ghz. However, if the test scenario you use has factors that prevent htis, it might skew your results. I recommend if you want to see the true performance of this machine, you test while plugged in.
 
I had the same issue before. After running down the battery to 0%, then recharge again to calibrate the battery, my MBA i7 2011 slows down a lot. Can feel it when running some flash-heavy games. Run Geekbench and it scores below 2000.

Reset System Management Controller of the MBA, and run Geekbench again, the score goes back up to around 6250 range.

To reset the SMC,
1. shutdown the machine.
2. connect to AC power.
3. on the built-in keyboard, press (left) Shift-Control-Option along with the power button once.
4. wait 5 seconds and press the power button to start the computer.

Hope the above helps.
 
One more thing...

the slow down, as measured by Geekbench, is repeatable, every time when I took the battery down to 0% for calibration purpose.

Resetting the SMC brings the speed of the machine up to what it should be, every time.
 
JTLING - you are a GOD! Thanks so much - it worked! You're absolutely right, I have hibernate mode turned off to save space on the SSD drive. My computer is now tripled in speed thanks to you. Shame on Apple for allowing this to even happen in the first place! But wow, what a huge difference. THANKS! :apple::apple::apple::apple:
 
drvelocity - good to know it fixes your problem. you can experiment with your MBA to see if the slow down occurs when the battery hits, says, 4%, or may be 3%. That happens to mine. Strangely, this never happens to 2010 model MBA, which I also have one, now being used by my wife.

Disabling hibernation mode with a system using SSD is always a good idea, as every time when the system hibernates, it writes the entire 4GB memory into your SSD. That's a 4GB file! That would take quite a beating on the SSD. Though with Lion, we have TRIM, still IMO, I don't think hibernation does matter to much to me.
 
drvelocity, can you elaborate on what effect hibernation being turned off has on your performance? It sounds like you're eluding to another post where hibernation was referenced, but I don't see anything about it.
 
Sorry, I should have been more specific - since I turned off hibernation mode completely to save the 4GB of space, if my computer ever ran out of batteries it would just cut out of the OS with no shutdown at all. That (expectedly) caused a spotlight reindex and a ridiculously slow computer until the spotlight index was finished, when it seemed to be "okay". But I never felt it was very fast compared to my old machine. The SMC reset must do something to jog the CPU into going back to normal speeds. Apple must not expect very many people to turn off hibernation mode I suppose, because this is a pretty annoying bug. Essentially I used this computer in 2005 mode for 6 months. :(
 
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