First post, by Sephiroth, The Great
Those motherboards are bad with the AGP GPUs compatibility and I don't know why people like them so much and consider them best of all time. When it comes to AGP compatibility they are bad.
I tested 3 motherboards: 2 440BX (Siemens Nixdorf D1107 and ECS P6BXT-A+ Rev.: 2.2E) and 1 440LX (VL-601).
And on none of those motherboards can Quadro2 Pro send video signal to monitor on boot (but it sends video signal on boot with 775Dual-VSTA normally).
Other tested by me GPUs (GeForce4 Ti 4200 with AGP 8x, Quadro4 980 XGL 128Mb, Asus GeForce4 Ti 4800SE and 2 different FX 5900XTs) were OK (they sent video signal to monitor normally on boot) on Siemens Nixdorf D1107 and VL-601 (maybe one of GeForces FX 5900XT had a little trouble to fully light blue LED lights on its fan but that is it).
But when I tested those GPUs on ECS P6BXT-A+ Rev.: 2.2E the results were tragic with all those GPUs. When I booted the PC it sometimes sent video signal to monitor and sometimes not with all those GPUs. Once it sent video signal to monitor and other time not with all those GPUs. With GeForce FX 5900XT I observed that sometimes it booted with this GPU and lighted blue LEDs on its fan and sent video signal to monitor and other time it did not light those blue LEDs and did not send video signal to monitor and other time it did only light them for a few seconds and then turn them off and not send video signal to monitor.
So ECS P6BXT-A+ Rev.: 2.2E is definitely the worst one.
It seems to be power delivery problems through AGP slot? It is definitely not a problem with a PSU. I tried and swapped a few different powerful PSUs and results are always exactly the same. Those motherboards have that poor power delivery through AGP slot? Quadro2 Pro is more power hungry/demanding than all those other newer GPUs?