Bandwidth question (120hz)

[XeaL337]

Hi guys, i'm thinking of getting one of the light boost monitors,
either the vg248qe or the benq xl2420te.

However, I'm currently running a laptop, which only has VGA and HDMI outputs.

After doing some research, it seems that VGA/HDMI cannot do 120fps @ 1920x1080.

I was wondering if VGA/HDMI had enough bandwidth to run a lower resolution (say... 1280x720) @ 120fps,
and whether either of these two monitors would support that (until i build a proper rig of course).

 

[dragonstongue]

VGA cannot that's for sure but HDMI can they are limited to 2560x1440 and because its such a short distance the Hz wont matter much.

That is if its a proper HDMI of course. 1920x1080 at 120Hz you would need a pretty good gpu to power that well enough, if you drop the resolution down then you "should" be able to run it BUT its a balancing act, if your cpu is doing a lot of the grunt work to power the monitor then it will be just as bad performance as a gpu trying to run to high of a resolution, well that and it would look like crap having a really high resolution monitor running at a low resolution just to get the higher Hz levels(doesn't make sense to me at all) smooth but crappy image quality, or not as smooth but great image quality.

Most monitors do not upscale or downscale very well keep that in mind.

 

[XeaL337]

My laptop card can do 1920x1080 @ 120fps. But it only has VGA and HDMI output which is why I am asking the question. I know VGA can do 100fps+ at 1024x768 but was wondering if the monitors in question support it. Same with HDMI, I know it can only do 1920x1080 @ 60fps but wondering if it can push say 1280x720 @ 120hz

 

[Mark Rejhon]

After doing some research, it seems that VGA/HDMI cannot do 120fps @ 1920x1080.

That's not necessarily true; it depends on the HDMI chips at both ends. I've seen people do 1080p@120Hz over HDMI, but it's not always guaranteed -- your computer might do 1080p@120Hz output, but the display can't. Or your computer can't but your display can. 1920x1080@120Hz is the same bandwidth as 4K@30Hz.

 

[XeaL337]

That's not necessarily true; it depends on the HDMI chips at both ends. I've seen people do 1080p@120Hz over HDMI, but it's not always guaranteed -- your computer might do 1080p@120Hz output, but the display can't. Or your computer can't but your display can. 1920x1080@120Hz is the same bandwidth as 4K@30Hz.

Oh OK, does anyone know if those monitors can do 120hz 1280x720 over VGAor could test it for me?

 

[nob0dey]

The Asus VG248QE has DP, HDMI, and DL-DVI.

No VGA sir.

 

[dragonstongue]

ok whos asking the question 2 people that are both 1 days olds?

the only way you will know if they can do 1280x1024 at 120Hz on YOUR system is to test yourself.

You did not specify the laptop that you have(and the type of video card it uses) so no answer seems a safe answer as am sure no one wants to misinform you.

I am terrible at match so am not even going to attempt to learn new numbers for this lol.
there is many things to read on this if you look enough.

Basically lets break this down.
why 120Hz? If your GPU can only shoot out 60 or less constant 120HZ is pointless as the gpu will be working harder, and taking a high resolution monitor and forcing the resolution down JUST to do 120Hz seems asinine IMHO anyways.
http://www.tomshardware.com/forum/331322-33-120hz-hdmi
again lots to read on this, VGA usually can hit resolutions(in regards to Hz that not even HDMI might be able to do)

lots to read up on this if you take the time to read on it and not ask for an easy answer in a yes or no type way, not trying to be rude but there is thousands of threads on google of people asking about this exactly.

So let us know your laptop or better the actual graphics display that it uses this should help to help your answer in one aspect however, less then 60 FPS constant don't worry about it you just wasting money thinking this, more then 120 well then that's different but 1080p at 120fps is quite hard to do in many games without a very powerful system to back it up, and reducing resolution is a "why would you do that unless you absolutely had to" type question.

 

[dragonstongue]

VGA can convert to DVI, DVI can go to HDMI/DP and so forth

 

[houkouonchi]

XeaL337 you would be better off telling us what actual videocard/laptop you have.

Quite a bit of misinformation here.

If its HDMI 1.3 spec it should be possible for it to do 1920x1080@120Hz.

Contrary to what people have said VGA can indeed do 120Hz at 1920x1080 the problem is finding a monitor that can actually accept and display that resolution/refresh rate over VGA (most will not).

Here is some real info with limits to let you have an idea of the limitations of things...

What resolution/refresh rate you can do is almost completely dependent of the amount of bandwidth you can push over the link (in pixelclock). Here are some pixel clock requirements for various resolutions (approximates as timings can make it very quite a bit).

1280x720@60Hz (75 Mhz pixel clock)
1280x720@120Hz (150 Mhz pixelclock)
1920x1080@60Hz (150 Mhz pixelclock)
1920x1080@120Hz (~300 Mhz pixelclock)
2560x1440@60Hz (~240 Mhz pixelclock)
2560x1600@60Hz (~265 Mhz pixelclock)
2560x1440@100Hz (~400 Mhz pixelclock)
2560x1440@125 Mhz (~500 Mhz pixelclock).
3840x2160@30Hz (~300 Mhz pixelclock)
3840x2160@60Hz (~600 Mhz pixel clock, usually via 2x 300 Mhz display port MST, 2x dual link DVI or 2x HDMI)
3840x2160@100Hz (~1000 Mhz pixelclock)


Ok so now that the resolution portion is mostly done. Here is the interface limits:

Single link DVI: 165 Mhz
Dual link DVI: 330 Mhz (although depending on cable/TMDS quality it can do 500 Mhz+)

HDMI 1.0/1.1/1.2: 165 Mhz pixel clock (signal compatible with DVI)
HDMI 1.3/1.4: 340 Mhz pixelclock (not signal compatible with DVI, cant use adapters)
HDMI 2.0: 600 Mhz pixelclock

Display port 1.1: 480 Mhz pixelclock
Display port 1.2: 960 Mhz pixelclock.

VGA: 400 Mhz pixelclock (Only really old video cards that are 10+ years old are lower).

So does this give you an idea? VGA supports a higher pixelclock than HDMI does. I used to run 2560x1920x63 Hz over VGA to a CRT which required 400Mhz of bandwidth (33% more than what is needed for 1920x1080@120hz).

The problem then comes with what the monitor takes.

You probably wont find any monitor that will accept 120Hz over VGA (I know a CRT that could do 120Hz @ 1600x1200 though).

A lot of 120/144 Hz monitors won't accept the full resolution/refresh rate over HDMI either a lot of times you *have* to use DVI.

If your laptop had a thunderbolt/displayport it would make things a lot easier. Your likely only option is finding a monitor capable of 120 Hz over HDMI. I think some of the yamakasi's could and maybe some other korean monitors can but I know a lot don't.

Using a HDMI -> DVI cable/adapter only is an option when your talking about 1920x1080@60Hz, 2560x1440 @ 41Hz, 3840x2160@18Hz. At any higher resolution/refresh rate DVI will be dual link (two TMDS) where as HDMI is always single-link (single TMDS) and thus are no longer compatible with each other at pixelclocks > 165 Mhz.

If the display will accept 120Hz @ 720p then that will be an option on any machine that has HDMI or DVI. The only display I know of for sure that can do this is the 50 inch seiki 4k display.

 

[houkouonchi]

Also op reading the manual of the ASUS VG248 it says:


Only DisplayPort and DVI ports support 3d feature given NVIDIA 3d Vision Kit is Available.


This kind of makes me worry about it being able to do 1080p@120Hz as just being HDMI really shouldn't matter. According to the spec summary it does say it has a HDMI v1.4 port, although it also says display port v1.2 and I seriously doubt that as they wouldn't need 1.2 bandwidth at all.

This is further evidenced by the resolution/refresh table table that only lists modes over 75Hz at 1920x1080 and DVI/DP only. It only shows 60Hz and stupid tv modes for HDMI so I would avoid this display as I doubt it will do 120Hz via HDMI.

Also looking at the spec sheet for the XL2420TE it doesn't appear this one will do it either.

Under horizontal frequency limits it lists 83 Khz for HDMI/VGA which is only enough for 1080p@60Hz where as its 140 Khz over dual link DVI/displayport.

So i dont think either of these monitors will work for you op. I think your best bet for >60Hz is one of the korean 1440p monitors which are similar in price and double the resolution.

I don't know which ones can do it over HDMI but I know the rev b catleap that had an HDMI port could do >60 Hz via HDMI.

 

[XeaL337]

Hi,
My video card is a nvidia 740M GT.
It can easily push 130/140+fps for the games I play, @ 1600x900

My laptop has VGA and HDMI outputs, but i wasn't able to find out which HDMI version it is. The model number of the laptop is Horize W650EH. It's got a nice 1920x1080 IPS display, which is why i'm complementing it with a fast TN.

So my card can definitely push the frames, the question i am asking is whether
*My VGA/HDMI port can output that much data
*A lightboost monitor can input that much data via VGA/HDMI

From houkouonchi's post it looks like i can definitely output enough, just need to find out if any of the lightboost monitors can input it.

Is it possible to go VGA->DVI? Though i'm guessing that won't work because you're pumping an analog signal into the monitor and not sure if the monitor can support it.

 

[houkouonchi]

Hi,
My video card is a nvidia 740M GT.
It can easily push 130/140+fps for the games I play, @ 1600x900

My laptop has VGA and HDMI outputs, but i wasn't able to find out which HDMI version it is. The model number of the laptop is Horize W650EH. It's got a nice 1920x1080 IPS display, which is why i'm complementing it with a fast TN.

So my card can definitely push the frames, the question i am asking is whether
*My VGA/HDMI port can output that much data
*A lightboost monitor can input that much data via VGA/HDMI

From houkouonchi's post it looks like i can definitely output enough, just need to find out if any of the lightboost monitors can input it.

Is it possible to go VGA->DVI? Though i'm guessing that won't work because you're pumping an analog signal into the monitor and not sure if the monitor can support it.

A GT 740M should definitely be HDMI 1.4. My macbook pro retina has an older (GT 650 M) which is HDMI 1.4 It can output 30Hz @ 3840x2160 on my 50 inch seiki and 120Hz @ 1080p. As you stated the problem will be finding a monitor that will do 120Hz over HDMI.

AFAIK there are no VGA -> dual link DVI converters. Also just like I am not aware of any HDMI 1.4 -> Dual-link DVI adpaters either. The cheapo passive adapters that convert HDMI -> DVI and DVI -> HDMI will not work as those are only for single link DVI.

 

[XeaL337]

Hi all,
I ended up getting a free CRT monitor, which displays 1280x720 @ 100hz. Much more cost efficient than getting a lightboost monitor! Lucky i didn't splurge, since G-Sync just got announced.

 

[jbltecnicspro]

Hi all,
I ended up getting a free CRT monitor, which displays 1280x720 @ 100hz. Much more cost efficient than getting a lightboost monitor! Lucky i didn't splurge, since G-Sync just got announced.

Out of curiosity (being a tube nut that I am) - what did you get?

 

[XeaL337]

Syncmaster 785MB, its not great but 100hz and no motion blur is awesome. I found a broken G420, i was so excite.. till it didnt turn on. I have another G420 at work, i might be able to scab that eventually