Active Displayport to Dual -Link DVI adaptor pixel clock

[jaylumx]

I am interested in buying one of these since AMD has no interest in supporting any pixel clocks above 330mhz over DVI. What is the highest pixel clock of an active displayport to dual link dvi adaptor out in the wild.

Any advice will be much appreciated

Cheers

[ToastyX]

The highest I know is around 400 MHz with this adapter: https://www.amazon.com/dp/B00856WJH8/?tag=mtests-20#ad

The problem is full-speed DisplayPort 1.2 is not common, and DisplayPort 1.1 actually has less bandwidth than unrestricted dual-link DVI. DisplayPort 1.1 only allows up to 360 MHz with 8-bit color and 480 MHz with 6-bit color. The driver will switch to 6-bit color beyond 360 MHz, but this isn't a major problem because AMD cards implement dithering. The driver might not allow beyond 360 MHz if the video card can't output 6-bit color. I know the 7000-series cards can output 6-bit color, but I don't know about the R9 290-series cards.

[jaylumx]

(04-11-2015 07:27 PM)ToastyX Wrote:  The highest I know is around 400 MHz with this adapter: https://www.amazon.com/dp/B00856WJH8/?tag=mtests-20#ad

The problem is full-speed DisplayPort 1.2 is not common, and DisplayPort 1.1 actually has less bandwidth than unrestricted dual-link DVI. DisplayPort 1.1 only allows up to 360 MHz with 8-bit color and 480 MHz with 6-bit color. The driver will switch to 6-bit color beyond 360 MHz, but this isn't a major problem because AMD cards implement dithering. The driver might not allow beyond 360 MHz if the video card can't output 6-bit color. I know the 7000-series cards can output 6-bit color, but I don't know about the R9 290-series cards.

Thank you for the reply. Is there a patch or work around that stops the driver from using 6 bit colour instead of 8 bit or is it a hardware limitation for the item in your link.

[ToastyX]

It's a DisplayPort limitation. I don't have any workarounds for DisplayPort limits. I'm not sure if a patch is possible because DisplayPort is packed-based and has fixed clock speeds.

[jaylumx]

(04-11-2015 09:25 PM)ToastyX Wrote:  It's a DisplayPort limitation. I don't have any workarounds for DisplayPort limits. I'm not sure if a patch is possible because DisplayPort is packed-based and has fixed clock speeds.

Thank you again for the reply.

[jaylumx]

I did purchase the item you linked to and i was able to achieve 100hz but it is 6 bpc.....just knowing that it is displayed in the catalyst control centre at 6 bpc bugs the hell out of me. Taking into consideration what you mentioned in your reply that adaptors use that bpc above 360mhz, i used a reduced timing in CRC for 90hz as well as 84hz which were bellow the 360mhz pixel clock and it still uses 6 bpc.

I wonder if there are any active Displayport 1.2 to DVI adapters out there?

[ToastyX]

Is the 8 bpc option not available when the pixel clock is not above 360 MHz? Are you able to get 8 bpc at all with the adapter?

I doubt there will ever be a full-speed DisplayPort 1.2 adapter because going beyond 330 MHz with DVI is not required for any monitor on the market other than the overclockable monitors.

[jaylumx]

(04-13-2015 02:32 PM)ToastyX Wrote:  Is the 8 bpc option not available when the pixel clock is not above 360 MHz? Are you able to get 8 bpc at all with the adapter?

I doubt there will ever be a full-speed DisplayPort 1.2 adapter because going beyond 330 MHz with DVI is not required for any monitor on the market other than the overclockable monitors.

I can only get 8 bpc to show when the refresh rate is 60hz. My 84 hz reduced timings only shows 6 bpc though which is surprising since its pixel clock is less than 330mhz.