• His Excalibur (Platinum)Radeon 9600 Dual-DVI 256MB Videocard with AGP slot. Other spelling variants of the same card are: HIS Excalibur Radeon 9600 Dual DVI, HIS 9600 Dual DVI
• Different versions:
  • Active cooling: http://www.revioo.com/articles/a4179_0.html (Cooling is only present on prototype/pre-series production models)¹⁾
  • Passive cooling with a Silicon Bridge DVI compliant transmitter: http://www.ati-news.de/HTML/Berichte/Enmic/R9600-Dual-DVI/His-R9600-Dual-DVI-Seite1.shtml ²⁾
  • Passive cooling with a THine Electronics DVI compliant transmitter ic from THine Electronics 'THC63DV164'³⁾

• Offical manufacturers webpage from Hightech.com.hk
• General info

• Flickering horizontal lines on second head of a dual-DVI system
• Last post: strong artifacts in 640x480 mode
• [radeon] can't do dual-link tmds, or second tmds transmitter …I have a picture over the DVI now, but it flickers pretty badly…
• ...The LCD still displays the vertical lines but I'll assume that goes away once loaded into and OS...

I found this problem is not only ATI/AMD related, but NVidia chipsets also seem to suffer from this problem, according to a google search with the following terms: “dvi output” “horizontal lines” “dual dvi”

• Gainward Ultra/780 XP with NVidia FX 5600 running both outputs at 1600x1200
• GeForceFX 5600, Second DVI shows gray lines

The artifacts with the HIS videocard with RV350 chipset tested with Ubuntu 8.04 are worse than under windows. While playing a videofile on the first screen, the 2nd screen is showing artifacts quite heavily.

Initially I suspected the glitches were caused by video memory which was not fast enough. At resolutions below 1600×1200 the video was fine on both outputs. Because at a high resolution with 1600×1200 pixels the memory timing may be more critical. If that would be the case, clean power would be critical, so I added exta 100nF decoupling capacitors on top of 4 of the 8 memory chips.

As the decoupling did not change anything at all, I had to look further. A second experiment would be slightly increasing the memory voltage, from 2.50 Volt to 2.55 Volt, by adding a resistor divider at a LM431 reference voltage ic (SOT-23). The voltage increase did not improve anything either.

Because from the two DVI outputs, only the second one had problems, I crossed my mind that a memory timing issue would not be a logical explanation. If it would be, then probably both outputs would suffer. Due to the differences in the DVI output circuitry, it made even more sense that the problem would be in something one of the circuits had which the other didn't have.