No "last core parallel slowdown" on OS X

Dave Bayer bayer at
Wed Apr 22 07:40:44 EDT 2009

My first post was comparing almost identical machines: Different Q6600  
steppings (the earlier chip makes a good space heater!) on different  
motherboards, same memory, both stock speeds.

In a few weeks when the semester ends, I'll be able to try Linux -vs-  
BSD -vs- OS X on identical hardware, and try Simon's settings.

(I do love overclocking, but five minutes improving Haskell code is  
generally more effective than a day tweaking motherboard voltages.  
We're too "green" to use A/C in the hot California summer, and this  
computer exhausts through a dryer hose out my office window as it is.  
I don't want it any hotter, I just want more cores!)

I do have some experience comparing this code on four different Linux  
boxes, and three different Macs, and Linux does consistently worse. I  
waited to post until I could compare 4 cores against 4 cores on nearly  
identical hardware.

Also, I tried many approaches to this code, and what I've been testing  
is my best version, which also happens to be one of the simplest  
approaches to parallelism. (It so often works that way with Haskell.)  
In fairness, I should also run the standard test suite used in the  

On Apr 21, 2009, at 10:14 AM, Tyson Whitehead wrote:

> Why not try booting a CD or thumb-drive linux distro (e.g., ubuntu  
> live) on
> your 2.4 GHz Q6600 OS X box and see how things stack up.  It would  
> certainly
> eliminate any questions of hardware differences.
> Cheers!  -Tyson

I can do even better: This $65 bay device takes four 2.5" SATA or SAS  

It has a surprising build quality, makes it trivial to juggle 2.5"  
SATA drives. Removing the high-low jumper disables the loud fan, which  
is probably only needed for SAS drives.

My primary drive is an OCZ Vertex SSD, for which this is perfect.  I  
also have an assortment of spare laptop drives I can use, so an OS  
survey will be easy.

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