OK, done some testing comparing the Rarewares 32 bit compile (ICL12.1) against my own VC10 32 bit compile (not ICL). Results are quite interesting (I think!!):
Microsoft Windows [Version 6.1.7601]
Copyright © 2009 Microsoft Corporation. All rights reserved.
F:\testdir>lame-vc9 -V 3 14.wav 14.mp3
LAME 3.99.4 32bits (http://lame.sf.net)
CPU features: MMX (ASM used), 3DNow! (ASM used), SSE (ASM used), SSE2
Using polyphase lowpass filter, transition band: 17960 Hz - 18494 Hz
Encoding 14.wav to 14.mp3
Encoding as 44.1 kHz j-stereo MPEG-1 Layer III VBR(q=3)
Frame | CPU time/estim | REAL time/estim | play/CPU | ETA
14177/14177 (100%)| 0:10/ 0:10| 0:10/ 0:10| 36.978x| 0:00
32 [ 1] *
40 [ 0]
48 [ 18] %
56 [ 630] %%%*****
64 [ 2172] %%%%%%%%%%%%**************
80 [ 78] %
96 [ 28] %
112 [ 39] %
128 [ 1081] %************
160 [ 5740] %%%%%%%%%%%%%%%%%%%%%%%%%%%%***************************************
192 [ 2469] %%%%%%%%%%%%%%%%%%***********
224 [ 454] %%%***
256 [ 1036] %%%%%%%******
320 [ 431] %%%***
-------------------------------------------------------------------------------
kbps LR MS % long switch short %
156.9 44.7 55.3 85.4 7.9 6.7
Writing LAME Tag...done
ReplayGain: 0.0dB
F:\testdir>lame-vc10 -V 3 14.wav 14.mp3
LAME 3.99.4 32bits (http://lame.sf.net)
CPU features: MMX (ASM used), 3DNow! (ASM used), SSE (ASM used), SSE2
Using polyphase lowpass filter, transition band: 17960 Hz - 18494 Hz
Encoding 14.wav to 14.mp3
Encoding as 44.1 kHz j-stereo MPEG-1 Layer III VBR(q=3)
Frame | CPU time/estim | REAL time/estim | play/CPU | ETA
14177/14177 (100%)| 0:10/ 0:10| 0:10/ 0:10| 35.327x| 0:00
32 [ 4] %
40 [ 35] %
48 [ 1022] %%%%%*******
56 [ 1640] %%%%%%%%%***********
64 [ 184] %%*
80 [ 25] %
96 [ 36] %
112 [ 30] %
128 [ 1050] %************
160 [ 5768] %%%%%%%%%%%%%%%%%%%%%%%%%%%%***************************************
192 [ 2477] %%%%%%%%%%%%%%%%%%%**********
224 [ 443] %%%***
256 [ 1032] %%%%%%%*****
320 [ 431] %%%***
-------------------------------------------------------------------------------
kbps LR MS % long switch short %
155.0 44.7 55.3 85.4 7.9 6.7
Writing LAME Tag...done
ReplayGain: 0.0dB
F:\testdir>lame-vc9 -V 5 14.wav 14.mp3
LAME 3.99.4 32bits (http://lame.sf.net)
CPU features: MMX (ASM used), 3DNow! (ASM used), SSE (ASM used), SSE2
Using polyphase lowpass filter, transition band: 16538 Hz - 17071 Hz
Encoding 14.wav to 14.mp3
Encoding as 44.1 kHz j-stereo MPEG-1 Layer III VBR(q=5)
Frame | CPU time/estim | REAL time/estim | play/CPU | ETA
14177/14177 (100%)| 0:09/ 0:09| 0:09/ 0:09| 38.541x| 0:00
32 [ 23] %
40 [ 1025] %%%*********
48 [ 1755] %%%%%%**************
56 [ 86] %
64 [ 28] %
80 [ 42] %
96 [ 302] %***
112 [ 1986] %%********************
128 [ 6081] %%%%%%%%%%%%%%%%%%%%%%%%%%%%%**************************************
160 [ 1267] %%%%%%%%%*****
192 [ 684] %%%*****
224 [ 500] %%%***
256 [ 366] %%***
320 [ 32] %
-------------------------------------------------------------------------------
kbps LR MS % long switch short %
121.0 34.6 65.4 85.4 7.9 6.7
Writing LAME Tag...done
ReplayGain: 0.0dB
F:\testdir>lame-vc10 -V 5 14.wav 14.mp3
LAME 3.99.4 32bits (http://lame.sf.net)
CPU features: MMX (ASM used), 3DNow! (ASM used), SSE (ASM used), SSE2
Using polyphase lowpass filter, transition band: 16538 Hz - 17071 Hz
Encoding 14.wav to 14.mp3
Encoding as 44.1 kHz j-stereo MPEG-1 Layer III VBR(q=5)
Frame | CPU time/estim | REAL time/estim | play/CPU | ETA
14177/14177 (100%)| 0:10/ 0:10| 0:10/ 0:10| 36.358x| 0:00
32 [ 2843] %%%%%%%%************************
40 [ 40] %
48 [ 8] %
56 [ 16] %
64 [ 32] %
80 [ 37] %
96 [ 316] %***
112 [ 1977] %%********************
128 [ 6070] %%%%%%%%%%%%%%%%%%%%%%%%%%%%%**************************************
160 [ 1265] %%%%%%%%%*****
192 [ 669] %%%*****
224 [ 510] %%%***
256 [ 357] %%**
320 [ 37] %
-------------------------------------------------------------------------------
kbps LR MS % long switch short %
118.2 34.6 65.4 85.4 7.9 6.7
Writing LAME Tag...done
ReplayGain: 0.0dB
F:\testdir>lame-vc9 -V 7 14.wav 14.mp3
LAME 3.99.4 32bits (http://lame.sf.net)
CPU features: MMX (ASM used), 3DNow! (ASM used), SSE (ASM used), SSE2
Resampling: input 44.1 kHz output 32 kHz
polyphase lowpass filter disabled
Encoding 14.wav to 14.mp3
Encoding as 32 kHz j-stereo MPEG-1 Layer III VBR(q=5.63333)
Frame | CPU time/estim | REAL time/estim | play/CPU | ETA
10287/10287 (100%)| 0:09/ 0:09| 0:09/ 0:09| 37.801x| 0:00
32 [ 1184] %%%%%%%******************
40 [ 905] %%%%%%*************
48 [ 20] %
56 [ 16] %
64 [ 71] %*
80 [ 1216] %%************************
96 [ 3250] %%%%%%%%%%%%%%%%%%%%%%%%%%*****************************************
112 [ 1811] %%%%%%%%%%%%%%%%%%%%%%****************
128 [ 783] %%%%%%%%*********
160 [ 627] %%%%%********
192 [ 230] %%***
224 [ 152] %%**
256 [ 21] %
320 [ 1] *
-------------------------------------------------------------------------------
kbps LR MS % long switch short %
95.0 36.1 63.9 86.1 7.8 6.2
Writing LAME Tag...done
ReplayGain: +0.1dB
F:\testdir>lame-vc10 -V 7 14.wav 14.mp3
LAME 3.99.4 32bits (http://lame.sf.net)
CPU features: MMX (ASM used), 3DNow! (ASM used), SSE (ASM used), SSE2
Resampling: input 44.1 kHz output 32 kHz
polyphase lowpass filter disabled
Encoding 14.wav to 14.mp3
Encoding as 32 kHz j-stereo MPEG-1 Layer III VBR(q=5.63333)
Frame | CPU time/estim | REAL time/estim | play/CPU | ETA
10287/10287 (100%)| 0:10/ 0:10| 0:10/ 0:10| 35.066x| 0:00
32 [ 2096] %%%%%%%%%%%%%*******************************
40 [ 12] %
48 [ 19] %
56 [ 11] %
64 [ 70] %*
80 [ 1217] %%************************
96 [ 3254] %%%%%%%%%%%%%%%%%%%%%%%%%%*****************************************
112 [ 1820] %%%%%%%%%%%%%%%%%%%%%%****************
128 [ 755] %%%%%%%%********
160 [ 634] %%%%%*********
192 [ 220] %%***
224 [ 157] %%**
256 [ 21] %
320 [ 1] *
-------------------------------------------------------------------------------
kbps LR MS % long switch short %
94.1 36.1 63.9 86.1 7.8 6.2
Writing LAME Tag...done
ReplayGain: +0.1dB
F:\testdir>
This track is neither particularly quiet, nor loud, but what is interesting is that the very quiet parts seem to attract a higher bit allocation with the Intel compile than with the VC10 compile. So, I'm guessing that with particularly quiet tracks, this accounts for the larger difference between the different compiles.