• 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 the first DVI output was fine, and the only the second DVI output had problems, I began to understand that a memory timing issue would not be a logical explanation. If it would be a timing issue, then both outputs would suffer.