I originally detailed the performance loss with my NEC card and K6-3/Voodoo3 PC on VOGONS:
https://www.vogons.org/viewtopic.php?f=46&t=73627 I was experiencing a performance loss of up to 40% in 3DMark99MAX/Quake2 and general CPU performance benchmarking software.
This was the case for simply having the card present (even when disabled in device manager). The only fix was removal of the card. The VIA card is much better in the K6-3 system, only really losing me a few % performance (1-3% depending on situation), but my older Pentium 200MMX system the VIA still lost anywhere up to about 7% system performance.
I've tested and see different results to you. Almost identical with and without the card connected.
Pentium III 550Mhz, Voodoo 3 3000G.
USB driver being used is Nusb36e.exe
Belkin 5 port USB 2 Hub card. NEC D720101GJ on the chip. P120101 - 6X3A on the card
Card connected and enabled in device manager.
Quake II timedemo 1, 800 x 600
73.6 fps
74.0 fps
73.8 fps
SiSoft Sandra 99 CPU benchmark
1472
732
PR658
P757
SiSoft Sandra 99 Memory benchmark
271 MB/s
250 MB/s
3D Mark 99 Max (default settings)
4371 marks
8158 CPU marks
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USB 2 Hub card removed from the machine
Quake II timedemo 1, 800 x 600
74.2 fps
74.1 fps
74.0 fps
SiSoft Sandra 99 CPU benchmark
1472
732
PR658
P757
SiSoft Sandra 99 Memory benchmark
272 MB/s
251 MB/s
3D Mark 99 Max (default settings)
4358 marks
8182 CPU marks