If you want an idea about what is possible for passive cooling see my favorite supplier of parts for making a silent PC: http://www.quietpc.com.

I had the cpu fan my a laptop (35W i5) die a while back.  Until I got it fixed, I had no choice but to underclock the CPU to run at a maximum of 1.2ghz.  In addition, I had to take the bottom lid off and expose the electronics the open air.  Otherwise, the CPU would hit 100C in a blink of an eye, shut down automatically and take 15 minutes to cool off before it would power back on.

Maybe those special cases where the entire case is one giant heatsink can cool down a 35W CPU enough but you have to spend the money just to experiment with the system.  With a 7.5W/10W Baytrail (Pentium J2900) or a 15W Haswell (Celeron 2955U), your odds of being able to passively cool the system will greatly increase.  However, you probably do need to drop the sample rates down a bit for these CPUs.  From my own experimentation with my forced-underclocked system, 22khz internal sampling + 44khz output device sampling will let you do about 200 polyphony (held down sustain pedal and pounded random keys nonstop).  44/44 though will drop notes unless you limit polyphony to about 100.

It is definitely a noticeable difference the further you lower buffer size, the lesser the round-trip latency. Buffer size is just one part of the whole latency figure. For piano this might not be a terribly huge deal, so 128 would work fine for pretty much anyone (512? no way in hell!). For a more direct instrument, like a guitar, lowest possible latency is necessary (64 or even 32).

I use Intel Pentium 2020M with passmark 2303, Pianoteq with optimistic polyphony setting, 256 samples, 44.1 kHz and my CPU load always < 50%.

I think every CPU with passmark > 2000 is OK for Pianoteq.

P. S. I think it's impossible to see any difference between 128 and 256 (and even 512) samples. You also shouldn't forget that even acoustic pianos have latency about 10-30 ms because of mechanics.

P. S. It's impossible to hear difference between 48k and 44.1k because of your ear limitation and Nyquist theorem. The only reason to use 48k is eliminating resampling if some device or software that process Pianoteq's output works in 48k (or multiple of).

Hello,
I agree with the fact that we can't hear a difference between 48k and 44,1k
I use to play at 48k to avoid this resampling.

Now for the samples, for me it makes a huge difference in the connection with the instrument. Since I am used to play at 128 samples, it is impossible for me to return to 256...

I think every CPU with passmark > 2000 is OK for Pianoteq.

P. S. I think it's impossible to see any difference between 128 and 256 (and even 512) samples. You also shouldn't forget that even acoustic pianos have latency about 10-30 ms because of mechanics.

P. S. It's impossible to hear difference between 48k and 44.1k because of your ear limitation and Nyquist theorem. The only reason to use 48k is eliminating resampling if some device or software that process Pianoteq's output works in 48k (or multiple of).

No way you can do fanless with a 35W CPU.

I will try that:

http://www.akasa.com.tw/search.php?seed=A-ITX10-A1B

It seems to be designed with an integrated fanless system for processors up to 35W of TDP.
On the specifications page they give the compatible CPU. It should be ok with a i5-4570T

I wonder what's the polyphony and minimum latency possible on that Baytrail.

In a large PC case, you will have to pick a 15W-17W CPU to do fanless.  Fanless will be very hard for a 35W CPU.

In a small form factor, fanless would require something from the even lower-powered families.  For example, the following is a 10W 2.4ghz quadcore Baytrail Atom designed for MINI-ITX cases and does not normally need a fan:

  http://www.newegg.com/Product/Product.a...6813135392

There's been successful reports of Pianoteq running on 2ghz Baytrails before (and unsuccessful attempts on 1.4ghz Baytrails) so the above will be fast enough.

Looking up the Pianoteq benchmarks I ran in off-line mode on my Baytrail server, a quad-core 2.4ghz Baytrail is roughly the speed of a dual-core 1.5ghz Broadwell.  The difference is you can get a full system running at 5W-10W on a Baytrail versus 15W-20W on a Broadwell.  Intel sells 6W Broadwells but they are capped at 600MHz so I'd pick a 6W 1.8GHz Baytrail over that anyday.

You should be fine with a 2 GHz dualcore, I think...

Thank you,

I have now a 2-core 2,53 Ghz on a laptop. It is a 5 years Pentium I5-460M. It works ok but then fan makes a lot of noise.

My question now is whether a new low TDP, for example an i5-4570T (TDP 35W, double 2,9Ghz) could do the job or not. Probably yes... with the advantage to keep cool with only a passive cooling system, so no noise a all.

But generally speaking, when the CPU frequencies are the same, are the new generation more powerful than the old? And also, a 2-core 3Ghz from AMD is it the same than a 2-core 3Ghz from Pentium?

You talk about Audio parameters, but nowhere do I see what audio device you are going to use.

The audio device and its drivers have a big impact on all the audio parameters, while at the same time even a modest modern PC or laptop has enough performance to play Pianoteq.

An external soundcard, Focusrite Scarlett 6i6

The audio device and its drivers have a big impact on all the audio parameters, while at the same time even a modest modern PC or laptop has enough performance to play Pianoteq.