4K + Vsync + VRAM

[AshleyAshes]

Okay, so on Friday I impulse purchased a Samsung 65" 4K TV, hooked up to my TV is an HTPC powered by am i7 3770K, Radeon HD 7950 3GB and there's 16GB of system memory.  Primarily this is an HTPC and it's done plenty of livingroom/couch gaming as well but I've been toying it out with 4K because... Why not?  Also, since I'm limited by HDMI 1.4a, I'm capped to 30hz until the DisplayPort adaptor I ordered arrives which will allow me to drive 4K @ 60 into the TV.

 

Obviously, I'm not stupid, when the GTX Titan XP can barely do modern 4K, I'm not expecting amazing 4K performance from a Radeon HD 7950, though Kodi is just fine (And that is it's primary application) and I've been testing it out on some older games.  I hit a wall however and that is VSYNC.  I can easily hit 30fps on max settings in say Portal 2 but I suffer input lag with Vsync on.  Setting the bar lower and I fired up Half-Life 1 in the classic GoldSrc engine and hit the same issue, it 'ran fine' but had input lag until Vsync was disabled.  If HL1 won't do 4K@30 with Vsync without input lag I can safely assume that almost nothing will.  Though Windows and Kodi seem just fine.

 

So this is more an academic question, I did expect to mostly game at 1080p and rely on the TV's upscaling options, but I'm curious if this is likely just due to the 3GB of Vram and that attempting to vsync a 4K image is just far too demanding on a card overall, regardless of the age of the game.

[ARikozuM]

You can set frame limits in most INI files.

[AshleyAshes]

5 minutes ago, ARikozuM said:

You can set frame limits in most INI files.

I don't see how that's very relevant to this...  You understand that the issue isn't about it running at 30hz right?

Though on that note, I'm testing some other games.  Screencheats seems to actually run fine with whatever vsych it uses.  Ikagura... Well, it SEEMS fine but also the game's entire engine appears to be locked to a 60hz refresh rate, so given a 30hz refresh rate the entire game is running at 50% speed.  It's fine except that it's like I just hit the Turbo button on my 486 to slow it from 66mhz to 20mhz.

[AshleyAshes]

5 minutes ago, CoolJ S.A.S. said:

For the VRAM, for games like half-life 1, probably not because of the textures size, effects, etc. are probably to low to require a buffer that large. 4k needs content tailored  for it to take full advantage of the resolution size, which was why when if you tested games like say far cry 3, you wouldn't see particularly high vram usage.  So it's unlikely that the 3gb is what's holding it back. 

Yeah, I def think it's more about the frame buffering but doing more testing it seems to vary by game.  Added to the list, while I can't see if it can hit 60fps until I get my DisplayPort to HDMI 2.0 adaptor, limited to 30fps, Rocket League runs like a stallion at max settings on this GPU.

[ARikozuM]

5 minutes ago, AshleyAshes said:

I don't see how that's very relevant to this...  You understand that the issue isn't about it running at 30hz right?

Though on that note, I'm testing some other games.  Screencheats seems to actually run fine with whatever vsych it uses.  Ikagura... Well, it SEEMS fine but also the game's entire engine appears to be locked to a 60hz refresh rate, so given a 30hz refresh rate the entire game is running at 50% speed.  It's fine except that it's like I just hit the Turbo button on my 486 to slow it from 66mhz to 20mhz.

My answer was mostly for the input lag issue. Upscaling has very little to do with VRAM as the TV's chip will manage that portion of the load. VSync can cause issues for games that run too well (Have you seen how bad Witcher 1 is on a 1080?) and slows everything down because of it.

[AshleyAshes]

Just now, ARikozuM said:

My answer was mostly for the input lag issue. Upscaling has very little to do with VRAM as the TV's chip will manage that portion of the load. VSync can cause issues for games that run too well (Have you seen how bad Witcher 1 is on a 1080?) and slows everything down because of it.

Er, I'm not upscaling anything, I'm testing all of this at 3840x2160.   My goal here is to figure out what DOES run at 4K on this GPU.

[ARikozuM]

Just now, AshleyAshes said:

Er, I'm not upscaling anything, I'm testing all of this at 3840x2160.   My goal here is to figure out what DOES run at 4K on this GPU.

Oh, I thought you were upscaling due to your 2nd paragraph. Input lag can be just as bad at lower rates.

[AshleyAshes]

1 minute ago, ARikozuM said:

Oh, I thought you were upscaling due to your 2nd paragraph. Input lag can be just as bad at lower rates.

No, I only meant that I obviously knew that a lot of games would never run at the TV's native resolution on this GPU.  Take GTA5 as a definitive example.  Not even worth trying.   That said, I have considered an FPS cap as you mentioned and I've enabled the FPS cap built into Catalyst and set it to 30fps to match the current 30hz refresh rate and will retry Portal 2.