0 Replies Latest reply on Aug 19, 2009 2:03 PM by bjorchard

    SDVO, DVI, and LVDS in laptop displays

    bjorchard

      Hello,

       

      I have a Dell Latitude D610 laptop with the Mobile Intel 915GM Express gaphics chipset and a LCD from Quanta Display, model QD14XL20. The chipset includes the Mobile 82915GM memory controller, and Intel 82891FBM I/O ocntroller hub, with the Intel Pentium M CPU. According to the spec for the graphics chipset, it supports multiple output types, such as analog CRT, digital LVDS (low voltage differential signaling), analog TV-out, and SDVO (serial digital video output). Note that SDVO supports DVI, LVDS, TV-out, and other formats. The LCD, according to the Quanta Display web site, evidently only supports LVDS. So this would very strongly suggest that the graphics data is sent from the motherbaord to the LCD via LVDS. Since LVDS is an electrical signaling specification, and not an encoding scheme, there is still the question of how the data is encoded. Since the order sheet from DELL says the display is SPWG (Standard Panel Working Group), which does specify an encoding scheme, I am currently assuming that this is how the data is encoded. Ok, so much for that part. Does this seem right to you? If so, there is one peice of info that throws this in some doubt.

       

      On the motherboard is a chip from Silicon Image, the SiI1362, a  SDVO (serial digital video output)-based DVI (TMDS) transmitter, aka PanelLink. Since there are no DVI output ports on the outside of the laptop and the display is supposedly only LVDS, what is this DVI transmitter doing, i.e., where is it sending its data? On the back of the laptop is a S-video TV-out port, which SDVO does support, but this should be distinct from DVI, so the question still would seem to be valid. This makes me think that possibly the SDVO-based DVI (TMDS) transmitter is sending graphics data to the LCD via LVDS with a 8/10 bit encoding (TMDS) scheme.  As you may be able to tell, knowing how the data is encoded as it passes from the motherboard to the LCD is of interesst to me. If you know the answer, I would be very appreciative.

       

      Another question. Looking at the high-level schematic of the SiI1362 chip, it takes SDVO data as input and passes out DVI-encoded data. Question #2: Does SDVO encode the data, i.e., do the data bits get reordered or reassigned, as happens, for example, wuth TMDS or the SPWG (standard Panel Working Group)  or VESA Flat Panel Display Standard? Most certainly the answer is"yes" but I need to confirm this. I understand that SDVO is an Intel propietary technique and am not seeking at this point the details - just knowing if there is an additional encoding and decoding of the data (beyond that associated with TMDS) associated with SDVO would be very helpful.

       

      Thanks,

       

      Brad