Avoiding hyperthreading

Hi all!

The manual’s hardware advice page advices against hyperthreading for low latency.

Is hyperthreading any case where the number of threads is higher than the number of cores? If so, if I had to choose between the slower 4-core 4-thread Intel i5-6300HQ and the faster 4-core 8-thread i7-6700HQ, would it be better to go for the i5?

I am trying to find a laptop for use in live music and have come across this choice in Entroware’s Kratos laptop in case that’s relevant…

From my experience the CPU and RAM are needed for internal digital calculations for program synths, samplers and effects. A real-time working with analog signals (with computer effects) and playing the program synth&effects through the keyboard requires a good sound-card. If you have no special sound-card (http://alsa-project.org/main/index.php/Matrix:Main), the great CPU can’t provide you a satisfied low latency (as I know). The (digital to analog) / (analog to digital) processing - is a question of sound device.

A helpful video about:

The basic story is this: it is all system-specific and cannot be predicted in advance.

More details: although a N-core processor may have N “cpus”, it doesn’t have N replicas of all the resources that a single-core processor would have. In particular, it does not have N floating point units (FPUs). Since audio processing is all done with floating point math, this means that by using hyperthreading, the hyperthreads on a single core, if they all need to use the FPU, are competing (and being serialized) for this resource. In theory, this will slow things down rather than speed them up.

In the real world, we’ve seen believable stories of hyperthreading having both effects: speed up and slow down. There appears to be no abstract way to predict the effect. My personal preference for a high performance (low latency) machine would be to disable it, but that may be incorrect on a given system.

I see I am a bit out of my depth here. Thanks for the clarification Paul, I now feel that it is not productive to fear hyperthreading until /after/ getting the laptop :smiley: