Thinkpads Forum

This is part of the "Starting over w/X61" thread, but it's got several sub-ideas that are (in my head) worthy of discussion separately [Moderators, if that's not ok please feel free to delete this].

Anyway, I just got a Unitek Y-3702 USB3.0 to HDMI adapter. When I plugged it into my X201, the first it told me it was a piece of DisplayLink hardware. Bad news for Linux, unfortunately.

The good news is that the software installed fine on the X61, but it did complain that the GMA950 might not be compatible. After holding my breath for a while, the "usb 3.0 display" exclamation mark in Device Manager went away. I then plugged in our HDTV which was successfully detected and presented to me in the Control Panel as a regular external monitor! I then set it as an extended screen AND IT WORKED! Resolution 1920 x 1080.

Now, performance. I installed GOM Player and downloaded some 1080p samples encoded at 10 and 18 mbps. They both play smoothly on the laptop's screen but are quite choppy on the TV. 720p Youtube is somewhat better, but I wouldn't watch a movie on it. Fine for presentations etc, which was my goal.

Questions for possible improvement:
- How to I measure USB bandwidth usage? I want to know if I'm saturating that, or something else. CPU usage is acceptable.
- As I mentioned in the other thread, I can install a mPCIe USB3 controller. It's not quite USB3 speed because it's PCI 1.0, but it should be about a 4x improvement over USB 2.0. Is that worth it?

R

USB saturation is always the cause, especially when you're trying to play videos.

I don't know how accurate this is, but perhaps the bandwidth required would be something like:

display resolution * color depth (in bytes/pixel) * display refresh rate

For example:
(1280 x 720) pixels * (4 bytes per pixel) * (60 frames per second) = 221,260,800 bytes per second

If the frames are fairly static (desktop, web pages, office productivity), it's likely that the HDMI adapter uses some form of interframe compression to send only the changed parts, so the slower USB 2.0 interface manages to keep up.

Even 250MB/s (PCI 1x) is probably too slow as axur explained. But if you look at his equation it becomes pretty clear that you just need to reduce the refresh rate to something like 30hz to get some major improvements.

Yup, don't disagree about the USB being the bottleneck. Do you have any suggestions as to reducing the refresh rate, or even setting it to something other than 50/60Hz at all?

R

EDIT: Found PowerStrip. At work now and don't have the adapter, but I'll play with it later.

From a small peanut in the gallery: You are the Man!

Reporting a slight failure. It seems PowerStrip doesn't like DisplayLink adapters (or GMA950s, for that matter). The external display is detected as "Generic PnP Monitor" in Powerstrip, and for both screens I cannot adjust the frame rate. The Advanced Timing Options are greyed out in all cases.
I have read that some people have had success with their GMA950s, so I'm wondering whether it's an application or a driver problem.
Any ideas?

R

So... There is no GMA950 on the X61. That's on the X60. The X61 has GMA X3100. Maybe that's the source of confusion?

Try running Powerstrip under XP.
That's what I needed to be able to 'flash' a 15" QXGA EDID.

Hm, new observation. On my X201, this same adapter runs much smoother at 1080p (although still not ideal) on the same screen that doesn't work well with the X61. While I'm not exactly surprised since it is a much faster machine and has a better GPU, this points to the USB connection NOT being the bottleneck. Also, the DisplayLink software uses a bunch of CPU (again, not surprised).
Any ideas?

R

Increased memory speed/bandwidth perhaps?
The X201 has DDR3-1066, plus the Core i5's integrated memory controller greatly reduces latency.

The X61 has a DDR2-667 memory controller on the GM965 northbridge, connected to the Core 2 Duo CPU through a 200MHz quad-pumped Front-Side Bus.

Probably. Let's see if it gets any better once I do the overclock modification.
Meanwhile, I also found that the converter has a heatsink on it that makes it slightly too tall to hide in the PC card slot... will have to think about installing an alternate sink and investigate how the thing is attached.

R

Actual USB throughput depends considerably on the CPU speed - that much is known.