About the HDMI/DVI issues, heres an overview of my (possibly incorrect) understanding, for those wondering (Note the resolutions listed can be fudged a bit by messing with display rate, ie it may be possible to get a single link dvi to display 24401400 @ 33hz)
DVI-A/I/D Single link supports up to around 1920x1200
* DVI-I/D Dual Link supports 2560x1600+
* HDMI <=1.2 supports up to 1920x1200
* HDMI 1.3 supports up to 2560x1600
* HDMI 1.4 supports up to 4096×2160
* HDMI1.3 intro'd different category cables, cat1 and cat2 (Sometimes called 'High Speed'). cat2 supports the higher res.
HDMI and DVI Single Link are compatible (you can get simple adaptors and hdmi-dvi cables). Note, single link only, ie HDMI to DVI adapter connected to a dual link cable and display will be act like DVI Single Link
HDMI w/Type B connector and DVI Dual Link are compatible, however as far as I know there were no HDMI Type B products ever made.
So you cannot convert HDMI>DVI to achieve 2560x1600
* To get 2560x1600 over DVI, you need a dual link card, display and cable
* To get 2560x1600 over HDMI you need a card with a >1.3 port, display and a >1.3 cat2 cable.
* Additionally, regardless of the HDMI standard supported by your card, it may not be capable of outputting 2560x1600 (The presence of a display port or dual link DVI is a good indicator)
So in theory most modern setups should support 2560x1600 over HDMI. In practice not so much, a few problems:
* Some displays and adaptors may claim to support >1.3, or not specify the version, and actually be <1.3
* Some displays and adaptors may be >1.3 but limit what they will output or display.
* Some displays may be >1.3 but report a lower max resolution in their EDID. Bypassing this/setting a custom mode may work just fine.
* Even if you do manage to get everything working together, you may experience general instability and errors.
TL;DR avoid HDMI for high resolutions if you can, it'll save you a lot of hassle.
To add to this problem, some graphics cards (such as ATI/AMD's Eyefinity) only have two display clocks and cannot output over hdmi/dvi without a special active (non-passive) adapter.
I don't doubt this info, it jives with what I know, but I know that HD4000 will not drive this display over HDMI on my friends mobo (which coincides with the other anecdotes I've seen).
Sorry I meant to include this about the HD4000, you're totally correct. It and it's 3rd gen sibling actually support HDMI1.4, but fall into the 'Some displays and adaptors may be >1.3 but limit what they will output or display.' category, unfortunately.
Here's my rudimentary/half forgotten understanding gleamed from the PCH datasheet and random internet browsing:
* HDMI/DVI both use TMDS and share the same encoding/formatting for video and control. The Intel chipsets defines 9 TMDS lines for a port which are identical/interchangeable between the HDMI/DVI ports: 3 Data pairs, 1 control pair and the hot plug detection.
* The 3 data pairs, the control/clock pair and the hotplug pin form the connections of a single link DVI-D connector.
* The DVI spec identifies the max pixel clock of a single link DVI connection as 165Mhz
* Higher pixel clock requires dual link, via an extra 3 data pairs, which are not defined by intel in the datasheet
* HDMI uses a single link connection, with 3 data pairs, control pair, and hotplug. (Except type B connections which were dual link, but never actually produced by anyone)
* HDMI <= 1.2 defined a maximum pixel clock of 165Mhz (same as DVI). So at this point the video and control data is compatible with DVI, same pins and max clock
* HDMI1.3 upped it to 340Mhz over a single link. Which is incompatible with DVI, which increased max res by adding more lines, rather than change the existing ones
This is where I make a bit of a leap: as far as I know, since the lanes used for HDMI/DVI are defined interchangeably, they are limited to a max clock of 165Mhz, the DVI maximum.
So even though these cards are listed as HDMI1.4, the video data produced is effectively maxed at DVI-D single link/HDMI<=1.2 compatible.
TL;DR again: the intel HD graphics (Specifically the HD4000 and HD2500, but assumably the earlier ones as well) are limited to single link DVI-D and the equivalent pixel clock over HDMI, effectively 1920x1200. DisplayPort does doesn't share this. If you have an Intel adaptor, and want >1920x1200, you're gunna want to use DisplayPort.
DVI-A/I/D Single link supports up to around 1920x1200
* DVI-I/D Dual Link supports 2560x1600+
* HDMI <=1.2 supports up to 1920x1200
* HDMI 1.3 supports up to 2560x1600
* HDMI 1.4 supports up to 4096×2160
* HDMI1.3 intro'd different category cables, cat1 and cat2 (Sometimes called 'High Speed'). cat2 supports the higher res.
HDMI and DVI Single Link are compatible (you can get simple adaptors and hdmi-dvi cables). Note, single link only, ie HDMI to DVI adapter connected to a dual link cable and display will be act like DVI Single Link
HDMI w/Type B connector and DVI Dual Link are compatible, however as far as I know there were no HDMI Type B products ever made.
So you cannot convert HDMI>DVI to achieve 2560x1600
* To get 2560x1600 over DVI, you need a dual link card, display and cable
* To get 2560x1600 over HDMI you need a card with a >1.3 port, display and a >1.3 cat2 cable.
* Additionally, regardless of the HDMI standard supported by your card, it may not be capable of outputting 2560x1600 (The presence of a display port or dual link DVI is a good indicator)
So in theory most modern setups should support 2560x1600 over HDMI. In practice not so much, a few problems:
* Some displays and adaptors may claim to support >1.3, or not specify the version, and actually be <1.3
* Some displays and adaptors may be >1.3 but limit what they will output or display.
* Some displays may be >1.3 but report a lower max resolution in their EDID. Bypassing this/setting a custom mode may work just fine.
* Even if you do manage to get everything working together, you may experience general instability and errors.
TL;DR avoid HDMI for high resolutions if you can, it'll save you a lot of hassle.