View Single Post
Old 08-11-03, 02:12 AM   #156
nutiu
Registered User
 
Join Date: Jul 2003
Posts: 3
Default

I hope my post will be more on the informative side for people who are still trying to verify whether they have a problem on their FX card or not.

I have downloaded flicker.dem as posted on page 4 and tried it out on my MSI FX5900U (nv reference design board) and found the flicker issue.

Here's my hypothesis as an electrical engineer, but I may be wrong:

1. This seems like an analog signal integrity issue. It is unlikely that any driver/BIOS update will fix it, UNLESS Nvidia has some control over the power supply from the software. It seems that the framebuffer contents are indentical, but the RAMDAC is doing something funky.

2. This may be related to "cutting" the FX5900U length from reference design that was about 1" longer. I see that a lot of decaps have been removed from the shipping product. This can compromise the quality of clean power supply to the ASIC.

3. I was not noticing this problem until someone showed me how (using UT2003's flicker demo).

4. To see what this problem looks like when it is happening: try autodetect in 3-D clock settings. The 2-D screen's brightness will have intensity modulation. I have a hypothesis on why this causes the symptom as well: During "autodetect" the ASIC is sinking power like crazy, thus any power supply deficiency will show up.

5. I also have a slight noise during screen scroll in IE. I haven't bothered to check where the noise is coming from, though, but I actually thought it was kinda cool although this looks like another power supply issue.

6. I didn't feel that this symptom annoy me that much. May be I haven't run into the case where it would.

System spec: Power supply is Enermax 450W w/fan speed control, mobo is ABIT IC-7G with 2x512MB Corsair RAM. CPU is 3.0 P4C. Abit's hardware monitor is showing 12V rail at 11.98 and not fluctuating, although I haven't hooked up a scope to some node near the ASIC's power input pins (I have to remove the rear heatsink to do it, and am too lazy to do so).

Finally, I am *surprised* that nvidia is surprised when someone informed them of this issue. They have got all the resources and know the power consumption of their ASIC and their card's power supply capability. May be their 3rd party card's manufacturer cut some corners?
nutiu is offline   Reply With Quote