USB to DVI vs Minidisplayport to DVI?

[Gata]

Hello, everyone.

Recently, I got my MBP hooked up to a 22-inch monitor via USB-to-DVI. The monitor's @ 1080p.

However, I noticed that when I play the itunes visualizer or any other video fullscreen, the frame rate makes it choppy. If I go into expose and make the video smaller, it looks fine.

I was looking into using the MiniDisplayPort to DVI adapter to see if that'd fix things.

I'd also tested a game on the other monitor. It plays fine on my mac on fullscreen, but on the other monitor at the same resolution (1400*900), the video was choppy.

So, would it be a worthwhile upgrade to move from USB to Minidisplayport for my setup w/ an external monitor?

 

[Mal]

You'll always get better results by far when using a dedicated video out instead of a USB port. USB uses the CPU, so the GPU is crunching the data to send to the CPU which crunches it again in a different way and then sends it out to the USB-to-DVI adaptor which has to then convert it into a usable signal. With Mini Display to DVI, it's taking the signal straight from the GPU and putting it on screen.

There's no comparison really. The only reason anyone should ever use a USB-to-DVI converter is if they need more than one external display, and they should never attempt to play video on it.

jW

 

[Gata]

You'll always get better results by far when using a dedicated video out instead of a USB port. USB uses the CPU, so the GPU is crunching the data to send to the CPU which crunches it again in a different way and then sends it out to the USB-to-DVI adaptor which has to then convert it into a usable signal. With Mini Display to DVI, it's taking the signal straight from the GPU and putting it on screen.

There's no comparison really. The only reason anyone should ever use a USB-to-DVI converter is if they need more than one external display, and they should never attempt to play video on it.

jW

Makes sense. Thanks!

Also, for anyone that's tried, is there any noticeable slowdown between your MBP and an external monitor when it's been hooked up via MiniDisplayPort?

 

[ctyhntr]

MiniDisplayPort to DVI works great for me. I bought one of those USB to DVI converters, it made my machine slow and the screen lag was noticeable. So, watching videos was out, at least I could settle for using it with XCode. I check Activity Monitor and it was using anywhere from 28-50% of the CPU.

 

[Mal]

Makes sense. Thanks!

Also, for anyone that's tried, is there any noticeable slowdown between your MBP and an external monitor when it's been hooked up via MiniDisplayPort?

Nope, never had any lag because of that. It's possible to overtax your GPU more while running two displays, but you'd have to really try.

jW

 

[Freyqq]

basically:

mini-DP(1000mb/s or so bandwidth)->GPU
vs
USB (20-30mb/s or so bandwidth) ->CPU->GPU

as you can see, there's a lot more slowdown with the USB connection

a mini-dp -> dvi cable is just a different set of pins. It is entirely passive.