projects:repair:his_radeon_9600_dual_dvi
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| projects:repair:his_radeon_9600_dual_dvi [2008/10/26 17:58] – admin | projects:repair:his_radeon_9600_dual_dvi [2009/01/21 17:10] (current) – admin | ||
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| * Passive cooling with a THine Electronics DVI compliant transmitter ic from THine Electronics [[http:// | * Passive cooling with a THine Electronics DVI compliant transmitter ic from THine Electronics [[http:// | ||
| - | ===== References to card ===== | + | ===== Searching the internet for clues ===== |
| + | ==== References to card ===== | ||
| * [[http:// | * [[http:// | ||
| * [[http:// | * [[http:// | ||
| - | ===== References to card related problems ===== | + | ==== References to card related problems ===== |
| * [[http:// | * [[http:// | ||
| * [[http:// | * [[http:// | ||
| Line 15: | Line 16: | ||
| * [[http:// | * [[http:// | ||
| ===== Related references to cards from other brands ===== | ===== Related references to cards from other brands ===== | ||
| - | I found this problem is not only ATI/AMD related, but NVidia chipsets also seems to suffer from this problem, according to a google search with the following terms: "dvi output" | + | 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" |
| * [[http:// | * [[http:// | ||
| * [[http:// | * [[http:// | ||
| + | ==== Linux ===== | ||
| + | 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. | ||
| - | ===== Linux ===== | + | ===== Experiments |
| - | ATI graphic card chip is from RV350 series | + | ==== Video memory decoupling ==== |
| + | Initially I suspected glitches were caused by jitter on data from video memory. At resolutions below 1600x1200 the video was fine on both outputs. The glitches would only manifest at high resolution above 1600x1200 pixels. So memory timing might be more critical. If that would be the case, cleaner power may solve the problem. So I added extra 100nF decoupling capacitors on top of 4 of the 8 memory chips. | ||
| + | |||
| + | ==== Increasing video memory voltage ==== | ||
| + | As 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. | ||
| + | |||
| + | ==== Inspecting DVI transmitter ==== | ||
| + | Because from the two DVI outputs, only the second one had problems, it crossed my mind that somehow a memory timing issue would not be a logical explanation. If it would be, then likely both outputs would suffer and not only one of them. Due to the differences in the DVI output circuitry, it made even more sense that the problem would be in something specific one of the circuits had which the other didn't have. | ||
| + | So I started to measure power supplies for the DVI transmitter, | ||
| + | |||
| + | ===== Solution ===== | ||
| + | To solve the problem with glitches, replace 47uF capacitor C1421 with a larger capacity. I tried several type of capacitors and it seemed that 470uF would be sufficient. The voltage across the capacitor | ||
projects/repair/his_radeon_9600_dual_dvi.1225040280.txt.gz · Last modified: 2008/10/26 17:58 by admin
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