Originally Posted by Gallien
The monitor you have on the way isn't 120hz w/1440p
. All of these 120hz OC'd monitors have been an illusion. They max out at 85hz due to hardware limitations.
Huh? If youre talking about the 85hz pixel limit from Nvidia and the newest drivers - that limit has been removed thanks to ToastyX. Hardware wise monitor/cable/gpu can definately hit 120hz+.
Here's discussion from one of the enthusiasts in the community - check it out here: http://www.overlordforum.com/viewtopic.php?f=8&t=65
Don't bother with overclock.net for information. They won't let anyone talk about these monitors, so a lot of the information is outdated and incorrect. Some people were claiming 2560x1440 @ 100-120 Hz is not possible with DVI because they didn't understand where the limitations were coming from. They didn't even test one of these monitors to verify what they were saying.
Let's start with the official DVI standard. The DVI standard states that single link implementations must be limited to 165 MHz or less, and anything greater than 165 MHz must be split across two links. Unfortunately, many people have misinterpreted that to mean each link is limited to 165 MHz for a total of 330 MHz with two links, but that's not true. In fact, the DVI standard specifically states, "there is no maximum for the dual link implementations."
That leaves four possible sources for limitations:
3. Video card
4. Video drivers
Let's start with the cable. Most dual link cables are designed to handle at least 330 MHz, which effectively means 330,000,000 pixels per second. TMDS uses 8b/10b encoding, which means 24-bit color is transmitted using 30 bits per pixel. That's where 7.92 Gbps and 9.9 Gbps comes from. 7.92 Gbps (330,000,000 * 24 = 7,920,000,000) is the amount of data transferred, and 9.9 Gbps (330,000,000 * 30 = 9,900,000,000) is the amount of bandwidth used to transfer that data. That is the MINIMUM. Most cables can handle more than that. If you reach the limits of what the cable can handle, you will start seeing artifacts like flickering lines or colored pixels. It will not lose frames.
The amount of bandwidth used includes blanking, which includes the period between each line and each frame that isn't shown on the screen. 2560x1440 @ 60 Hz is typically sent as 2720x1481 @ ~59.95055 Hz to make the pixel clock 241.50 MHz, so 2720 * 1481 * ~59.95055 = 241,500,000 * 30 = 7,245,000,000 = 7.245 Gbps
Now on to the transmission of the data from the video card to the monitor. The video card sends a constant stream of data. At higher refresh rates, the data is sent faster. It's not possible for frames to get lost. If the monitor or the cable can't handle the faster data rate, the monitor won't be able to process the data and you won't get a usable picture. Some monitors do process the data and skip frames at higher refresh rates, but I've already proven that's not the case with the single-input models (see pictures below).
As for the monitor itself, the main board with the DVI input has a DVI receiver that is designed to handle at least 450 MHz, which is enough to get 109-114 Hz, depending on the timing parameters used. That's not quite enough for 120 Hz, but the receiver can usually handle more than designed. The receiver takes the DVI input and sends the data to the timing controller board using quad channel LVDS output, which can easily handle the data rate. The timing controller then sends the data to the panel. The LVDS timing controller made by LG is the one that can handle high refresh rates. The monitors that can't overclock have a DisplayPort timing controller made by Parade.
Now on to the video card. Most video cards made in the last few years have TMDS transmitters that can handle at least 225 MHz per link. That also gives us 450 MHz with two links, but most TMDS transmitters can handle a little more than designed, and some newer ones can handle 300+ MHz per link. 120 Hz requires around 468 to 497.76 MHz, depending on the timing parameters used.
The biggest obstacle has been the video drivers. Even though the hardware is capable, both AMD/ATI and NVIDIA have placed limits in their drivers:
AMD/ATI's driver limits dual-link DVI to 330 MHz, which is only enough to get 81.92 to 85 Hz, depeneding on the timing parameters used.
NVIDIA's driver originally allowed 500+ MHz with 600-series cards, but SLI and older cards were limited to 400 MHz, which is still enough to get 97-102 Hz, depending on the timing parameters used. After 301.42, they implemented a 330 MHz limit for all cards.
By now, I have managed to remove most of the limits from both drivers. Patchers are available here:
AMD/ATI Pixel Clock Patcher
NVIDIA Pixel Clock Patcher
See the Quick Start Guide.
Older NVIDIA cards are still limited to 400 MHz, but I managed to remove the SLI limit yesterday, which allows SLI to work beyond 100 Hz with 600-series cards. Basically, no matter what the setup, you should be able to get at least 97 Hz no problem.
At this point he includes pictures as proof, a camera shutter set to 1/10th of a second - and you can clearly see the 120hz has twice as many frames than the 60hz. So theres math you can check and pictures you can see - that took me about a minute to dig up.
And yes, my monitor i ordered was from Overlord - which uses the same pcbs as the old 2Bs. I have no doubt that it will physically output 120hz at 1440p.Edited by jerrolds - 9/25/12 at 4:22pm