About AmigaAMP, AHI and the speed of it

People keep telling me to include a Paula playback routine because they think AHI is degrading the performance too much.

I keep telling people that a correct AHI configuration is crucial if you don't want to end up with a completely overloaded system.

Now I finally performed some tests myself. Here are the details:

Test #1: System used for testing:

  • Hardware:
    • Amiga 3000
    • GVP G-Force 68040-40
    • 16MB RAM
  • Software:
    • MPEGA 3.4 (22.06.98) [Generic]
    • mpega.library 2.0 (22.06.98) [68040/60]
    • ahi.device 4.180 (31.10.97) 68020+ version
    • TinyMeter V4.31
    • AmigaAMP v2.1
AHI unit 0 has been configured to Paula:Fast 8 bit stereo++ 22050 Hz, one channel.
AmigaAMP has been configured for 32KB loading buffer, 1/5 second playback buffer.
MPEGA was started just by giving the -d and the -q option, nothing else.

mpega (no AHI) AmigaAMP (AHI)
FreqDiv = 2
Quality = 0
Stereo
 72% CPU load
no problems
 73% CPU load
no problems
FreqDiv = 2
Quality = 1
Stereo
 78% CPU load
no problems
 78% CPU load
no problems
FreqDiv = 2
Quality = 2
Stereo
 90% CPU load
no problems
 89% CPU load
no problems
FreqDiv = 1
Quality = 0
Stereo
 100% CPU load
interrupted playback
 100% CPU load
interrupted playback

Test #2: System used for testing:

  • Hardware:
    • Amiga 3000
    • Phase5 CyberStorm PPC 68060-50, 604e-200
    • 48MB RAM
AHI unit 0 has been configured to Paula:Fast 8 bit stereo++ 44100 Hz, one channel.
I used only the 680x0 versions of both mpega.library and AmigaAMP.
Everything else same as above

mpega (no AHI) AmigaAMP (AHI)
FreqDiv = 1
Quality = 2
Stereo
 42% CPU load
no problems
 47% CPU load
no problems

As you can see, the results are almost the same for both programs! I didn't expect such similar values myself. Now I'd say AHI is better than its reputation concerning CPU usage for plain playback. Of course, CPU load rises when you use extra gimmicks like volume boost, pannning, etc.

If the configured mixing rate in AHI prefs is different from your playback rate, AHI will start to resample on the fly, consuming lots of CPU power, leaving painfully sounding aliasing artifacts. In the HiFi modes the quality is far better but the CPU demands are even higher.

Now please stop moaning and start to configure your system properly! :-)

Everyone sending me an email, complaining about slow AHI will get a full copy of this page in return...


Thomas Wenzel, 26.06.1998