Running a 4k screen using a Radeon HD 5450
I was the lucky recipient of a 4K monitor recently (an ASUS MX27UQ). So the question of how to drive it arose.
In order to run it at its full resolution of 3840x2160, with a 60Hz refresh rate, I assumed I was going to need a new graphics card, so started looking around. I wanted something fairly low powered (I only have a 150W power supply), silent and less than £50.
It quickly became apparent that I would need a DisplayPort 1.2 card, which supports that resolution. The most common HDMI standard at the moment is 1.4, which only supports 3840×2160 at 30Hz. There are very few HDMI 2.0 cards available (which supports 60Hz), and they're all very expensive.
I wasn't looking to do any gaming, so didn't need anything very powerful. I was looking for cheap and quiet. That combination proved elusive though, with most cards either having a fan, not enough resolution, being quite expensive or no longer available.
I was leaning towards a new motherboard as the cheapest option. This MSI board seems to have all the right specs and I almost bought that, except I realised it's the CPU that's responsible for the graphics and my G3258, which doesn't even have a version on its Intel HD graphics, wasn't going to cut it. I'd need to buy an i3 chip at least, which made the whole bundle way more expensive than a graphics card alone.
I considered an external, USB option, such as the Plugable USB 3.0 to DisplayPort 4K UHD. I was close to pulling the trigger when I realised it was only 30Hz, despite being DisplayPort. It was cheaper than most of the internal options though.
During my research I found some suggestions that even a Radeon HD 5450 could output the required resolution, albeit at only 30Hz. I figured if I was only going to get 30Hz (without spending more than I wanted and/or sacrificing to noise), I might as well explore this option. There was this comment on a VisionTek card, for example. There was also this thread at Hard Forum. There were other places too, but every time I checked the official stats on manufacturer's websites they said otherwise. Even AMD's own spec sheet says otherwise.
I already had this Sapphire HD 5450 card already, running my 30" screen, but I couldn't pick anything higher than 1920x1080 when I plugged my new screen into the HDMI port. I wondered if I could force a higher resolution somehow. Neither the Windows tools or Catalyst Control Center would let me pick it or create a custom resolution.
That led me to an application called Custom Resolution Utility (CRU), which fills in the hole left by all the default software. As it turns out, the resolution I wanted already appeared in the list it exposed. The notes in that forum post suggested I would need to patch my driver to allow a faster pixel clock. This allows for higher resolutions and refresh rates.
The notes included a link to something called the AMD/ATI Pixel Clock Patcher. It was simple enough to run and, immediately after patching it and restarting the driver (using the tool supplied with CRU) I was able to pick 3840x2160 (at 30Hz) from the resolution option in windows.
I'm limited to 30Hz because it's connected via an HDMI port, but it's perfectly liveable. The other bonus is I can still run my 30" at full resolution too. All without spending any more money.
If you're not a gamer, but want to make use of 4k, it's worth a look into what you can force your current card to do, as you might be surprised. This is a GPU that was released in 2009!