DisplayPort 1.3's copious bandwidth lets UHD content shine
Although we can't share many details of them yet, AMD gave us a high-level overview of its next-generation Radeons last week. One of the tantalizing features baked into these upcoming GPUs is support for DisplayPort 1.3 with the High Bit Rate 3 link option. This type of DisplayPort link offers a whopping 32.4 Gbps of bandwidth, about 80% more than HDMI 2.0, and it can move all those bits using existing cables and connectors. DP 1.3 has several exciting implications for next-generation FreeSync displays, as well as for higher-resolution panels like 5K screens.
For one, DP 1.3 can drive 4K (or 3840x2160) displays with full color data at up to 120Hz. DP 1.3 also allows a graphics card to drive a 5K (5120x2880) display over a single cable at 60Hz with full RGB color. Consider that a 5K display has 78% more pixels than consumer 4K displays, and you start to get a feeling for just how much data is moving across that single DisplayPort 1.3 link.
That extra bandwidth isn't just for driving gobs of pixels, though. A theme of AMD's summit was making "better pixels," not just more pixels. By AMD's definition, better pixels will be produced with a wider color gamut and a broader dynamic range. To guide this effort, the company has taken a page or two from the burgeoning ultra-high-definition (UHD) segment of the consumer electronics industry .
UHD content can be produced with an extremely wide color gamut (Rec. 2020). UHD also uses a modern transfer function (SMPTE ST 2084) to encode a wider range of brightness values for UHD TVs and monitors, commonly known as high dynamic range, or HDR.
For reference, AMD says typical consumer displays today range from about 0.1 to 250 nits of brightness. Those displays also use the relatively narrow sRGB color space and a transfer function designed to mimic the characteristics of CRT displays (Rec. 1886). That function only accounts for a brightness range up to 100 nits, and it's poor at encoding the darker parts of an image.
UHD OLED displays could boost that maximum brightness to 500 nits (with pure blacks, thanks to the underlying display technology), while future LCDs could range from 0.0005 to 1000 or even 2000 nits next year. Those LCDs are will likely use local backlight dimming to acheive higher contrast.
10-bit color support is a rarity on today's displays, but AMD expects it'll be a key feature of displays going forward to support the wider color ranges required by UHD content.
Another piece of the UHD puzzle on the PC is Windows' support for 10-bit color and HDR. Right now, Windows offers limited support for 10-bit applications, and the OS doesn't support HDR content at all.
AMD says it can get around these issues for the moment by rendering UHD content in an exclusive full-screen context, since that mode bypasses Windows' limitations. That's not an ideal situation, but it should work fine for activities like gaming and movie-watching that are generally full-screen in the first place. As UHD content becomes more common, we'd expect that Microsoft will develop more fine-grained ways of handling and displaying that content outside of a full-screen context.
Today's Radeon graphics cards will be able to support UHD gaming and photos, while those next-generation Radeons with HDMI 2.0a and DisplayPort 1.3 will be able to output 4K UHD content (including movies) at up to 60 frames per second with 10 bits per color channel.
The Radeon Technologies Group had a couple of UHD displays running HDR at its tech summit to demonstrate UHD content, and we were impressed by the clearer, more natural-looking images these displays showed, especially next to a (frankly broken-looking) conventional HDTV. The ugly tone-mapping that might have reared its head in older games on conventional displays was nowhere to be seen. UHD will probably get a lot of hype from consumer electronics companies soon, but based on these quick previews, we think these displays (and the content they'll show) will be an exciting advancement.
You can see some examples of the higher refresh rates and different content types that DP 1.3 monitors may support in AMD's image above. We're most excited about the expected specifications of those 2560x1440 and 3440x1440 displays. 170Hz or 144Hz HDR content with FreeSync enabled? Sounds great.
Don't expect these panels to hit the market immediately, though. AMD projects that single-cable-ready 5K displays will arrive in mid-2016, while 120Hz 4K panels with FreeSync support are expected to arrive in the fourth quarter of 2016. Even so, these higher-refresh-rate displays sound like they could herald a bold new era for the gaming monitor, and it'll be interesting to see what GPUs AMD has up its sleeve to drive them.
FreeSync goes mobile, too
Gaming notebooks with Nvidia's G-Sync onboard have been available for a while, and now AMD is getting in on the mobile variable-refresh game from a somewhat more entry-level angle. The one qualification is that any discrete Radeons must be driving the laptop's internal display directly, not through an Intel IGP. The company unveiled the first of these notebooks, a FreeSync-enabled version of Lenovo's Y700 laptop, at its summit.
This machine has a 15.6" 1080p display that can run in a VRR range of 40 to 60Hz. While it's nice to see FreeSync make its mobile debut, we've got to pick a nit. Given the demands of FreeSync's LFC tech, we'd have loved to have seen a display with a broader refresh-rate range, like 30 to 75Hz at a minimum.
This particular Y700 is a fairly nice-looking machine that's powered by an FX-8800P APU and Radeon R9 M380 graphics. The FreeSync panel doesn't use a scaler chip, a typical configuration for a notebook. Instead, AMD uses some of the FX-8800P's resources as a display controller to make the VRR magic happen.
AMD didn't provide the full specs of this red-blooded Y700, but we did some investigating for an idea of what this machine's $899 list price gets you. The R9 M380 graphics chip uses 10 GCN compute cores for a total of 640 stream processors, clocked at a round 1000MHz. AMD's specs say the M380's 128-bit memory bus can be joined to up to 4GB of GDDR5 memory running at up to 1500MHz. Based on those specs, the M380 should slot in somewhere between the GeForce GTX 950M and GTX 960M.
Mobile G-Sync is only available in notebooks with GeForce GTX 965M cards and better, and notebook makers seem to have reserved the feature for the $1500-ish price bracket, so Lenovo's Y700 could represent a nice way to get VRR on the go for less. It remains to be seen how many other manufacturers will hop onto the mobile FreeSync bandwagon.