Re: anyone running @ 64 buffer size?

[Rainer Straschill <moinsound@googlemail.com>]

FRO DIDDLY schrieb:
> if i can run @ 128 with a dual core, should i be able to run 64 with a 
> quad core? ;oD im sure that logic does not hold its weight, but where 
> does the bottleneck occur for digital audio processing?
>
> i know to use a firewire card with the texas instrument chip set-
> i know to avoid the motherboard display output and use a separate 
> video card-
Basically (and others did in part already tell you so - would expect 
Andy Butler to chime in here soon ;), every component in the chain from 
audio interface to your application (and back) plays its role here. This 
is (without any claim of completeness):
    * communication chipset of the interface ("your audio card")
    * communication protocol from interface to computer (e.g. firewire)
    * computer-sided communication adapter (e.g. firewire card/adapter 
in the computer)
    * system architecture of the computer (i.e. how the data gets from 
the adapter to the cpu)
    * computer BIOS
    * computer OS
    * computer's adapter driver
    * any layers in between driver and application (e.g. ASIO)
    * application

And then there's of course the CPU speed...

Now theory would say that using some dedicated interface structure will 
bring down your required buffer size. I had the best experiences with 
RME HDSP technology (which is a proprietary interface for some of their 
older interfaces, e.g. multiface (II)/digiface) and can easily reach a 
buffer size of 64 on my Kentsfield-equipped computer.
The reason is that a lot of the components in this chain are done by RME 
(who take great pride in their designs, and rightly so), in that case 
everything from the (ASIC) communication chipset, the communication 
protocol (RME's own design and optimized for that application), the 
computer-side adapter and the drivers, and the adapter interfaces 
directly to the PCI(e) bridge, and that is usually designed well on most 
computers.

There's also manufacturers who build audio-optimized computers - 
basically something you can do yourself if you spend days on end 
researching the necessary info. The best idea may be to define the 
unmodifiable starting points for your system (e.g. if you definitely 
need/want to use your specific audio interface) and then build around 
those conditions, considering some of the ideas you mentioned. You can 
in some cases also be lucky with some non-TI firewire chipsets, and also 
with an onboard graphics adapter...so make sure to try before you buy 
(and in the best case using the exact hardware/software setup you intend 
to use).

Some other tricks:
    * DPC latency is an important parameter. Setup your computer 
including audio interface and use this tool: 
http://www.thesycon.de/deu/latency_check.shtml
    * there are interfaces that work well with USB2. RME's earned good 
reports, but I also had success with the (discontinued) Marian UCON. 
Most of the time, USB is a problem on Macs.
    * Depending on your OS, use the means at your disposal to optimize 
it for audio. Caveat: there's a lot of sites out there which give you XP 
(or earlier)-optimized suggestions under the "Vista" or "Windows 7" 
header. But generally, turning off everything you do not need (NICs, all 
of those odd services, Aero etc.) is a good idea.


          Rainer

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