Hi again:

Just to test I've plugged it to a 9-years-old Compaq Presario 2510EA laptop and works fine...0 crackles.

Now I'm even more lost.

Yes, I already checked the latency with the DPC and as you say, it reported (very high) red spikes up to 16k and the "some device drivers on this machine behave bad and will probably..." message. After the scan I went to the device manager in Windows and checked every hardware was correctly recognized and the drivers up to date... couldn't think what else to do!!

Now I'm running the LatencyMon v 3.00 (didn't know this) and it shows a intense red "your system appears to be having trouble..." message too. Since I'm not familiar with the software, I don't know how to readt the data or what to do to solve the problem, so I hope you can give me some guidelines.

And of course, thanks for the help!!

Oh my God... according to that I have serious problems. All the values are far beyond the 4000 µs!!

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The "stats report" are:

CONCLUSION
_________________________________________________________________________________________________________
Your system appears to be having trouble handling real-time audio and other tasks. You are likely to experience buffer underruns appearing as drop outs, clicks or pops. One or more DPC routines belonging to a driver running in your system appear to be executing for too long. Also one or more ISR routines belonging to a driver running in your system appear to be executing for too long. Also your system appears to be having trouble which may be attributed to SMI routines, CPU bugs or unexplainable CPU stalls.
LatencyMon has been analyzing your system for 0:06:14 (h:mm:ss)

_________________________________________________________________________________________________________
System Information
_________________________________________________________________________________________________________
Computer name:                                        PC
OS version:                                           Windows 7 , 6.1, build: 7600
CPU:                                                  GenuineIntel Intel(R) Core(TM)2 Quad CPU    Q6600  @ 2.40GHz
Logical processors:                                   4
RAM:                                                  8588353536 total
VM:                                                   2147352576, free: 1795424256

_________________________________________________________________________________________________________
CPU SPEED
_________________________________________________________________________________________________________
Reported CPU speed:                                   2400 MHz
Measured CPU speed:                                   2386 MHz

Note: reported execution times may be calculated based on a fixed reported CPU speed. Disable variable speed settings like Intel Speed Step and AMD Cool N Quiet in the BIOS setup for more accurate results.

_________________________________________________________________________________________________________
MEASURED KERNEL TIMER LATENCIES
_________________________________________________________________________________________________________
Highest measured kernel timer latency (µs):           16137.6136

_________________________________________________________________________________________________________
MEASURED SMIs AND CPU STALLS
_________________________________________________________________________________________________________
Highest measured SMI routine or CPU stall (µs)        9282.4451

_________________________________________________________________________________________________________
REPORTED DPCs
_________________________________________________________________________________________________________
Highest DPC routine execution time (µs):              18617.7112
Driver with highest DPC routine execution time:       ntoskrnl.exe - NT Kernel & System, Microsoft Corporation

Highest reported total DPC routine time (%):          1.8613
Driver with highest DPC total execution time:         ntoskrnl.exe - NT Kernel & System, Microsoft Corporation

Total time spent in DPCs (%)                          2.6481

DPC count (execution time <250 µs):                   1524217
DPC count (execution time 250-500 µs):                0
DPC count (execution time 500-999 µs):                6150
DPC count (execution time 1000-1999 µs):              1867
DPC count (execution time 2000-3999 µs):              2806
DPC count (execution time >=4000 µs):                 0

_________________________________________________________________________________________________________
REPORTED ISRs
_________________________________________________________________________________________________________
Highest ISR routine execution time (µs):              12051.3637
Driver with highest ISR routine execution time:       hal.dll - Hardware Abstraction Layer DLL, Microsoft Corporation

Highest reported total ISR routine time (%):          0.1094
Driver with highest ISR total time:                   dxgkrnl.sys - DirectX Graphics Kernel, Microsoft Corporation

Total time spent in ISRs (%)                          0.3370

ISR count (execution time <250 µs):                   716374
ISR count (execution time 250-500 µs):                0
ISR count (execution time 500-999 µs):                1129
ISR count (execution time 1000-1999 µs):              310
ISR count (execution time 2000-3999 µs):              212
ISR count (execution time >=4000 µs):                 0

_________________________________________________________________________________________________________
REPORTED HARD PAGEFAULTS
_________________________________________________________________________________________________________
Process with highest pagefault count:                 none

Total number of hard pagefaults                       626
Hard pagefault count of hardest hit process:          412
Highest hard pagefault resolution time (µs):          105360.1354
Total time spent in hard pagefaults (%):              0.4302
TODO: Number of processes hit:                        0

_________________________________________________________________________________________________________
PER CPU DATA
_________________________________________________________________________________________________________
CPU 0 ISR count:                                      462225
CPU 0 ISR highest execution time:                     12051.3637
CPU 0 ISR total execution time:                       2176619.2500
CPU 0 DPC count:                                      1311390
CPU 0 DPC highest execution time:                     16591.7062
CPU 0 DPC total execution time:                       12754623.8624
_________________________________________________________________________________________________________
CPU 1 ISR count:                                      85335
CPU 1 ISR highest execution time:                     10944.4424
CPU 1 ISR total execution time:                       841167.3262
CPU 1 DPC count:                                      76507
CPU 1 DPC highest execution time:                     14420.4675
CPU 1 DPC total execution time:                       8522426.2312
_________________________________________________________________________________________________________
CPU 2 ISR count:                                      84898
CPU 2 ISR highest execution time:                     11612.4074
CPU 2 ISR total execution time:                       1003799.5950
CPU 2 DPC count:                                      66532
CPU 2 DPC highest execution time:                     18617.7112
CPU 2 DPC total execution time:                       9068796.5587
_________________________________________________________________________________________________________
CPU 3 ISR count:                                      85670
CPU 3 ISR highest execution time:                     10343.9137
CPU 3 ISR total execution time:                       1026918.6937
CPU 3 DPC count:                                      82921
CPU 3 DPC highest execution time:                     14883.7120
CPU 3 DPC total execution time:                       9317775.9740

OK, I'm working on that... I'll say something as soon as I know.

By the way, you say about the nVidia driver: what about ntoskrnl.exe?? I don't know what it is, but it gets the highest values.

Thanks again.

Have you tried legacy 1394 driver?

Also, what is exactly the model/manufacturer of the 1394 controller card? Does it have Texas Instrument chip or others like VIA, Ricoh, Jmicron?

I've tried the legacy driver again and now the results are different: it seems to work fine but instead of crackling, both the sound and the video start playing in fast motion (funny). Pause+resume and working fine again... until next time.

oh, okay....how about the DPC latency spikes?

I know, but at least, you can isolate the problem is with the PCI card/driver or something else.
I usually check DPC latency test before installing anything (cards, software, peripherals), and spend a day or two to see if I don't get any strange spikes overnight. BIOS tweaks are done right after the installation of OS and video drivers. Optimizing this way, I know what kind of add on caused problems.

Hi again:

After a thousand tests at home and with the problem going on, I decided to take the computer to the support center, hoping they could find a solution. As they had told me, it seems to be a incompatibility problem between the motherboard and the graphic card... both of them Gigabyte HeadScratch, so they are going to test different motherboard-graphic combinations to see if the can solve the problem.

Jeff told in #7 "NVidia is often a bad choice for DAW use lately", so I would like to know which is the best option for using Cubase, Kontakt, BFD2... and whatever that could come (one never knows). It should have more or less the same specs/price than the GT440 and offer the same results, since I use the PC not only for "music making/playing" but also for general purpose: listening music, watching video, surfing the web and sometimes even playing video games.

Thanks again!!