[LAU] Box under £400

Robin Gareus robin at gareus.org
Thu May 31 11:14:34 UTC 2012

On 05/31/2012 07:16 AM, Gabriel M. Beddingfield wrote:
> On 05/30/2012 09:21 AM, Sciss wrote:
>> thanks for the link and the info. so you think atom processors are
>> fine enough? the latency actually doesn't matter in my case. i'm more
>> worried that i'm going to through a lot of CPU heavy stuff on it, as
>> this will run experimental software I wrote myself (and I won't have
>> any time for performance tuning of the software itself).
> I have an Atom N450 netbook.  In practical terms, its limits for a
> single task are:
>   * Time-stretching a clip in realtime to 50% to original
>     time span.
>   * A set with 4-5 monophonic synths, and 4-5 pure audio
>     tracks.
>   * All of the Renoise sample programs
>   * Most anything you can throw at Mixxx.

Interesting! Thanks for sharing.

> While it has very good audio performance -- it has significantly less
> headroom than a Core2 or i-series processor (feels like a factor of 2 or
> 4).
> Other non-audio tasks:
>   * Large compiles take 4-6x longer (e.g. kernel, Qt)
>   * Number crunching tasks are very slow.  It's like the
>     floating point stuff is driving drunk.


>   * Processor has a high performance hit for inefficient
>     memory access (compared to Core2, i-series).

Clearly. i5 has 8192KB L1 cache.
I have not seen an ATOM CPU with more than 512KB.

>   * Processor doesn't benefit as much from SIMD (SSE)
>     optimizations.  E.g. you're lucky to get a 2x performance
>     boost using SIMD instructions... whereas a Core2 or i-series
>     will see at least a 2x performance boost.
>   * Most Atom devices have only 1GB RAM (2GB if you're lucky).
>     I've not seen an Atom device with more then 2GB.

Only a few Atom models support >2GB. The D525 for instance does.

> Finally, all this experience is in 32-bit mode.  I've been running in
> 64-bit mode recently, but haven't done much audio with it.  Overall, it
> feels about the same.

For audio (read: jackd) 64 bit should make no difference. It's all 32
bit floats, anyway.

The Atom D525 that Egor and i recommended is not that bad. I don't have
access to an Atom N450, but the N270 is waaaay /slower/:

Here's a quick jconvolver benchmark:

 A - Intel(R) Core(TM) Duo CPU  @ 1.66GHz (32 bit - 2 cores, 2 CPUs)
 B - Intel(R) Core(TM) i5 CPU   @ 2.80GHz (64 bit - 4 cores, 4 CPUs)
 C - Intel(R) Atom(TM) CPU D525 @ 1.80GHz (64 bit - 2 cores, 4 CPUs)
 D - Intel(R) Atom(TM) CPU N270 @ 1.60GHz (32 bit - 1 core,  2 CPUs)

1) `jackd -d alsa -p1024` ;
    4 instatances of `jconvolver weird.conf` in series
    first and last instance connected to system:*

    A:  CPU-load:  16% (all CPUs)  jack-DSP-load: 7.1%

    B:  CPU-load:   6% (all CPUs)  jack-DSP-load: 6.2%

    C:  CPU-load:  13% (all CPUs)  jack-DSP-load: 10.6%

    D:  CPU-load:  56% (all CPUs)  jack-DSP-load: 24.9%

2) `jackd -d alsa -p64`
    4 instatances of `jconvolver weird.conf` in series
    first and last instance connected to system:*

    A:  CPU-load;  27% (all CPUs)  jack-DSP-load: 13.0%

    B:  CPU-load:   8% (all CPUs)  jack-DSP-load: 7.3%

    C:  CPU-load:  18% (all CPUs)  jack-DSP-load: 20.3%

    D: -- jconv exit with 2nd instance: processor can't keep up ---


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