I had C7.5.10 (C7.5) running stable on a Win7 SP1 machine. Upgraded to a new machine running Win8.1. C7.5 started generating audio and MIDI glitches. Could see from the Performance Meter that although the “average” usage (the green bar) never moved much beyond about 10%, the “real-time peak” usage (the blue bar) would unpredictably jump to the right lighting the virtual overload LED and the playback of MIDI and Audio would glitch.
I’ve now installed the new machine as dual boot Win7 and Win8.1 and can run C7.5 (with identical preferences) under both of them. Here’s the result of the experiments (in all cases the Yamaha FW buffer is set to “small” – the default):-
Win7
Firewire: VIA Driver (NOT legacy)
Yamaha FW Driver: 160 Samples
ASIO Guard: enabled
Steinberg Power Scheme: enabled
Performance Meter Green Bar: never exceeds 5%
Performance Meter Blue Bar: never exceeds 80% (and then only occasionally and momentarily)
No audio or MIDI drop outs. C7.5 perfectly stable.
Win8.1
Firewire: VIA Driver (NOT legacy)
Yamaha FW Driver: 160 Samples
ASIO Guard: enabled
Steinberg Power Scheme: enabled
Performance Meter Green Bar: never exceeds 15%
Performance Meter Blue Bar: frequent random peaks to 100% lighting the virtual overload LED
Repeated audio or MIDI drop outs (average about 4 or 5 a minute).
Win8.1
Firewire: VIA Driver (NOT legacy!)
Yamaha FW Driver: 160 Samples
ASIO Guard: disabled
Steinberg Power Scheme: disabled
Performance Meter Green Bar: never exceeds 10%
Performance Meter Blue Bar: frequent random peaks to 100% lighting the virtual overload LED
Repeated audio or MIDI drop outs (average about 3 or 4 a minute).
Win8.1
Firewire: VIA Driver (NOT legacy!)
Yamaha FW Driver: 256 Samples
ASIO Guard: disabled
Steinberg Power Scheme: disabled
Performance Meter Green Bar: never exceeds 5%
Performance Meter Blue Bar: frequent random peaks to 100% lighting the virtual overload LED
Repeated audio or MIDI drop outs (average about 2 or 3 a minute).
Win8.1
Firewire: VIA Driver (NOT legacy!)
Yamaha FW Driver: 512 Samples
ASIO Guard: disabled
Steinberg Power Scheme: disabled
Performance Meter Green Bar: never exceeds 2% (barely visible)
Performance Meter Blue Bar: frequent random peaks to 100% lighting the virtual overload LED
Repeated audio or MIDI drop outs (average about 1 or 2 a minute).
Not until the Yamaha FW driver is set to more than 2048 samples does the real-time peak meter not at some point during the playback jump suddenly to the 100% overload and cause a glitch. Of, course, at that sample rate recording live MIDI is impossible.
Using the legacy FW driver in Win7 and Win8.1 on this machine makes very little, if any, relative difference to these results.
There is clearly a big difference between the way C7.5 is handled under Win7 and Win8.1. Anyone thinking about upgrading should take warning.