Is 1600x900 possible over single channel LVDS?

Linus posted an interesting trick regarding monitor resolution and cables: https://plus.google.com/u/0/+LinusTorvalds/posts/HQsCY7ErAL4
It's a fun read, but the gist of it is that he managed to get 2560x1440 over single-link DVI (normally considered impossible due to bandwidth limitations) by halving the refresh rate of the monitor to 30 Hz, effectively halving the required bandwidth.

This got me thinking whether something like this would be also possible for internal connections like LVDS. For those of use with 1366x768 screens, the cable is likely a single-channel LVDS. A single-channel LVDS cable has just enough bandwidth to support 1366x768 @60Hz and so general consensus has been that you can't go over 1366x768.

But from a bandwidth perspective there's no reason why you can't do 1600x900 @40Hz or even 1920x1080 @30Hz over single-channel LVDS. The question is whether or not the graphics card will still send that information over a single-channel or try to send it over dual-channel regardless and whether the LCD panel will work properly.

Any LCD screen experts want to chime in?

 

Having a 1366*768 panel does not obviously mean you have a single channel LVDS, many laptop support many resolutions regardless of cable or graphics.

Some examples I have successfuly done: Elitebook 8540p stock panel 1366x768 -> 1920x1080 , no cable mod
Qosmio x300 1440x900 -> 1920x1200 no mod (backlight fn-f8 is inversed, don't know why)
Qosmio x500 1680x945 -> 1920x1080 no problem
Elitebook 6930p 1280x800 -> 1440x900 LED (with cables and PCB for the LED model, Panel is LP141WP3 from ThinkPad T410)

And many other panel replacements I have done...

And I have other examples... Many "consumer notebooks" in a same series range share the same motherboard, a 15.6 laptop and a 17.4" laptop from a same manufacturer and range use the same motherboard, an use interface boards (CD/DVD for examble) to adapt to the different chassis.

But they use 1366*768 for the 15.4" and 1600*900 for the 17.4", using the same mobo.

Look at the HP Compaq 6710b / 6510b:
6710b -> from 1280*800 to 1680*1050; 6510b 1280*800 to 1440*900, ALL using the SAME motherboard.

I refurbish many of these, and everything is interoperable... but, ok, we are having professional laptops here.

 

Its not just the graphics but how many channels the panel expects as well so 1080p panels read as 1080p but only display every second line.

 

Never had a problem on "half" resolution being displayed...

 

When you connect a single LVDS channel cable to a dual channel display that is what you get, many machines like acer have half the cables missing from the connector.

 

That's right, the thing is that I rarely replace the panel with a higher resolution panel on these machines, all I do is replace them when they are broken with same generic panels...

 

Not exactly an informative answer or good examples at all, all the laptops you've listed has higher resolution panel options from factory.

This is a good answer and fits how my Lenovo Y570's video cable is which a 40 pin dual channel LDVS connector getting split into 30 pin sinlge channel LDVS on the main board with 10 pins being used/reserved for the webcam.

Which translates into no go for anything over 1366x768 on my specific laptop despite it having a 40 pin dual channel LVDS connector.

@ OP

a) Check with the manufacture to see your laptop model comes with higher resolution options

b) Check online forums to see if others users are asking the same questions and have been able to swap for a higher resolution panel for your specific model

 

Ok. I think you guys are misunderstanding what I'm trying to do.

1. I'm well aware of the conventional wisdom concerning resolution upgrades. About how you need to see if there are oem upgrades available, checking the LVDS cable, etc, etc. That's not what this question is about. This is more a theoretical question.

2. I'm aware that 1080p panels require dual-channel LVDS. I wondering if it's possible to use a 1080p panel with an incompatible cable at less than full performance (similar to what Linus did). For example, if I got a 1080p panel, could I still drive it at 1366x768 over a single-channel cable? (regardless of how pointless you think this would be).


Meaker, in the example you gave you're trying to display a 1080p @60Hz, which obviously runs into bandwidth limitations regardless of what the panel expects. What if you did 1080p@30Hz or 768p@60Hz. Would it still not work?

 

No, you still get half the pixels missing at 1366x768 because the panel expects half the information on channel A and half on channel B, that's the way it and all dual channel LVDS displays expect their information, they don't have any cable sensing built in to move to a different number of channels.

 

So you'd have to modify the cable and split the channels from the 30 pin connector on the motherboard, but the y570 may not work as a guide since I'm guessing they planned it to work like that and there might be some kind of cable sensing circuit on the motherboard circuitry.

I believe the Sony SA/SB/SC series also uses a 30 pin motherboard connection with a 40 pin cable.

This is pretty intriguing to me and I think its worth some experimentation. I have some panels and laptops to mess around with. If anyone has a good idea of where I should get started and some datasheets I should look at please post them here

 

@ niffcreature

I'm aware but my splitting the cable to 30 pin to get connected to a 30 pin 1600x900 15.6" panel (which are available on the market BTW but highly overpriced to the the scarce nature of the panels), I will automatically loose function of my webcam which I'm not willing to sacrifice for a higher resolution on my Y570.

Thank you for the very informative and thoughtful suggestion (you're theory is right on the money for the Y570) however this topic has discussed to death over a year ago on the Y570 owner's thread and all (if not most) of us Y570 owner's have come to accept it's not worth the investment on a highly overpriced 30 pin 1600x900 15.6" panel plus splitter cable mod (double the price of normal 40 pin 1600x900 15.6" panels which do not work on the Y570) then loosing the HD webcam in process.

 

Which half of the pixels are missing? Vertical columns or horizontal rows?

 

sorry to interrupt the discussion, but I was interested in understanding some things: the dual-channel LVDS uses a 40-pin connector or a 30-pin? thanks..

 

Dual channel LVDS is always 40 pin for HD+ panels, HD = 720/768p and HD+ is anything over that regardless of aspect ratio.

However there are extremely rare laptops that have 30 pin single channel LVDS HD+ panels in them, mainly the Dell Latitude.

 

so, theoretically, if i have a 40-pin cable with the right wiring, can i use a lcd with resolution higher than 768p?

 

I guess that remains yet to be seen.

I see... did anyone suggest trying to run the webcam on USB? Maybe HD webcams are not USB, I was able to run my sony Z webcam with a normal USB cable soldered to the cables.

 

Theatrically yes however certain manufactures shorten the pin on the cable themselves (easy fix) or on the motherboard connector (pretty much no solution).

Please read Meaker's comment posted on the first page.

The best bet is if the specific laptop model is offered in a higher resolution from manufacturer and you just happend to bought the lower revision with a lower resolution and want to upgrade.

I haven't thought of that maybe because I did not want to short circuit anything by splitting the internal USB pins to the HD webcam and at the same time I'm not sure if the HD webcam is USB.

However, if the HD webcam is pcie then I can probably wire it to the extra mini pcie slot not added by Lenovo for the Y570 (reserved for TV tuner models however the spacing and flux is still there for DIY).

Might be a solution....hmmm

 

Unfortunately not my case.. I have an Acer Aspire 5745G with a normal 1366*768 15.4" display. I'm quite sure it has a 40 pin connector, and it has a dual channel lvds (it is stated on the disassemble guide), but no other model has an higher resolution. Unfortunately now that I work with some particular softwares this resolution is starting to get quite uncomfortable and I was thinking of replacing the panel with something bigger (like a fullhd)..

 

If it's dual channel LVDS, you should be able to upgrade the resolution up to 1080p. However I'm suspicious of the information in the guide since OEMs typically won't use dual channel if they don't provide higher resolution models. Like Nemix suggested, just because there's 40 pins doesn't mean they're all connected either.

 

I absolutely understand, but the guide I'm looking at is the disassemble guide which looks quite "official" for this model. However I guess that the only way to check this would be to open the notebook and phisically check the connector status. I found a scheme of the motherboard with the lvds part but more than observe that the 40 pins are present I couldn't state wether is dual channel or single.

 

Vertical columns.

There were some older models that used push pins into the conenctor (think molex or floppy power cable into the connector) you could then take a 40pin cable and swap over to the connector. These days they like to use smaller soldered connectors making this impossible.

 

First you'll have to find your laptop's schematics and check the LVDS connector. If all of the connections there are labeled, there's 99% chance that you are good to go and make custom LVDS cable. If only, say, 75% (30 out of 40) of them are labeled and the rest are blank/x/NC there's 99,99% chance that you're out of luck. Second - for the custom LVDS cable you'll need at least another set, or like in my case, a different dual channel LVDS one, with the same connectors. As Meaker mentioned it, a lot of the cables has soldered wires, so I took one that wasn't and have rearranged it. You'll also need the new panel's schematics as well, but in most cases the connections are standard, except some rare IPS, proprietary and so on, but you wont need them. It's like 3 hours job including the research for schematics and re/arranging the cable. A multimeter set to continuity would be useful in the process if you end-up rearranging another cable. I have successfully moved from 1280x800 (1ch.) to 1440x900 (2ch.). And yes, 5920G was only shipped with 1280x800 displays, hence I had to make custom cable.

 

I found something something like this:



looking at it seems that part of the connectors are unplugged..

 

That's what you need. Seems about right, if you ask me, but don't take it as a sure bet, you're the one to decide

 

thank you very much, that was just what I needed. do you know where I can find the correct scheme for the wiring of the cable?

 

If I was you, I'd buy either one of those two:
AUO B156RW01 V3 - matte
CMO N156O6-L02 - glossy
Feel free to choose among the rest
Here's the panel side of the connector:

 

I'm going to try out a 15.6" 1600x900 panel on my Y570 come the following week since there's a panel reseller in my country the offers exchange/refund and shipping insurance back to them and back to me again if it doesn't work on my laptop and I need a different panel.

My second choice is a 15.6" 1366x768 3D panel if the 1600x900 does not work out since in the service manual of my Y570 lists two 3D panels as compatible, even if I don't get the 3D itself to work for whatever reason and the panel still gives a full picture it might still be worth keeping the 3D panel over a standard 1366x768 panel since 3D panels have lower response time (2ms for the ones support on the Y570), higher contrast ratio, better blacks/colors and maybe possible to operate in 120Hz.

I'll see how it works out next week, if push comes to shove then I'll get the G770 video cable to see if works for 1600x900 on my laptop since the G770 has the exact same 40 pin split to webcam cable as my Y570 however the G770 comes standard and works with 17.3" 1600x900 panels so in theory with the G770's video cable my laptop should also work with 15.6" 1600x900 panels.

Come to think of it, of all the threads made on higher resolution panels on the Y570 nobody has actually tried a 15.6" 1600x900 panel on it, the only one user that tried out a 1080P panel and it did not work out.

 

Just make sure to ask for the exact part number when you are buying a display (if you want one of the above), prior buying it of course.

You better check both schematics - Y570 and Y770 in case their pin assignments are different, otherwise you can fry something.

 

No I'm not sticking in the G770's video cable in my laptop just yet, that would be my last desperate attempt; I've got free two way shipping back and fourth for exchanges and returns within 30 days.

I'd look into the cable difference matter further before I do something like that, besides the G770 cable costs $60 off eBay shipped so I'm in no hurry to try it out right a way since it costs as much as the new panel upgrade panel pretty much.

Edit:

Just placed order for B156RW01, I didn't want to go with V1 or V3 (took the original) since the higher versions have lower brightness and distribution (anything under 200 CD/m2 brightness is unacceptable for me) but have slightly better colors and contrast.

I could have also went with a LG panel which has the best colors for a 15.6" 1600x900 panel but has lower contrast, brightness and distribution.

The panel should arrive on Monday next week will report back then.

 

Update:

The screen arrived today and I plugged into my Y570, it's a no go. I get a picture and the resolution is correct however the colors are distorted (pink/green), I re-checked to see if my cables were loose but cable seems fine. Plugged in my old display and everything shows up correctly again (colors and resolution). Looks like I'll be using my free return shipping and trying the 3D 1366x768 screen that is supported in the Y570's service manual.

So there you have it like said by many of us on this thread, just because the laptop has a 40 pin connector it does not mean the laptop will support 2-channel LVDS (needed for 1600x900 or higher) on the motherboard and over the 40 pin cable.

 

The pink/green is a color space issue. It sounds like the the panel is trying to interpret the signal as YUV instead of RGB, which is very strange. I think this is the first time I've heard of computers using YUV rather than RGB.

That said, all the pixels are getting there, so there might be a way around the color space conversion. Maybe a driver issue?

 

Would this work?

LG:
LP140WD2-TLE1

PANEL DETAIL Panel Size :14.0 inch Panel Type :a-Si TFT-LCD Composition anel Resolution : 1600×900 Mode :TN, , Surface :, Brightness :250 cd/m2 (Typ.) Contrast Ratio :400:1 (Typ.) Display Color :262K Viewing Angle :70/70/60/60 (Typ.)(CR=10) Frequency :60Hz Lamp Type : WLED Signal Type :LVDS (1 ch, 6-bit) RoHS Compliance :Application : Notebook PC

 

I think that might be a typo. The panelook spec page says the pin configuration is LVDS-40P2C6B-010A

 

It is listed as 40pin one indeed, so what? Just for example, my stock display was 30pin, but only 20 were used (1280x800 1ch LVDS). Strange enough there is another "impossible" one - QD15AL01 rev 03 (1680x1050, 1ch LVDS). I don't know how it is possible, but since there are two, it could be. The only way is buy-and-try, if you have money for wasting

 

Can 1 display cable (laptop) support both, 1 ch and 2 ch lvds screens? So if my laptop has a 1 channel lvds display, it would be impossible to have a 2 ch display working without another cable?
Also, is it impossible to upgrade from a lvds display to an edp display?

 

Both, the 2ch and the eDP things are possible, but both are highly unlikely and the second requires A LOT (read it right - A LOT!!!!!) of work. Some laptops (VERY few) were shipped with low-res displays, but 2ch LVDS cables. As for LVDS to eDP - here's a "little" read (second post).

 

I would like to know if these two cables are different?

20455-040E-0# <-- this is used for 1600x900 40pin

20455-040E-12<-- this is for 1900x1080 40pin

my current laptop has 1600x900 40pin and i replaced it with the 1900x1080 40pin and the problem is that from boot the new screen is in RGB flash mode?(possible factory burn in mode?)

any thoughts??

thank you

 

Hi,
I have a dell 15R N5110 , 15.6" with res 1368x768 (HD), did any of you successfully upgraded to a higher resolution : 1600x1200 / 1920x1080 (FULL HD).
Do I need another LVDS cable ?

 

I've found this thread really interesting. I've just one question regarding this kind of modification, I own a Qosmio X500-14D with a defective motherboard (18.4" fullhd) and I've found a X500-102 with a better config but with only a 1680 x 945 screen. I wanted to change the complete screen (with inverter, LCD, etc...), I've checked on SparePartsWarehouse.com for others references and the mobo seems to be the same for 2 different types of screen, so it seems Toshiba does not change the mobo between 2 models.
So could you confirm me that this kind of modification is possible ?

 

Since the new one is running @1680 x 945, it's already Dual channel, so it should be straight swap assuming the pin order is the same. Make sure to use the new cable, as the old one might not have the same pin positions. The best way is to find both schematics and compare them. Again, I think that using the new cable with the old display would be fine, but as they say - better safe than sorry.

 

OK thanks for your reply, I'll give you some news when the swap will be done !

 

I was thinking about what you told me for the cable, and if the HD LCD has 2 CCFL (compared tto the other one with just 1 CCFL) it would be more logical to use the cable which comes with the HD LCD ?

 

Yes, but then you DEFINITELY need to check both schematics or you WILL fry something if they are not the same. Since it's Toshiba and their schematics are pretty scarce, there is another way around, but it's a bit time consuming.

First of all, are the connectors the same? If yes than we can continue to the next step.
All of the displays have standard input terminal - display's LVDS connector. It means that both displays have the same pin-out.
You'll need a multimeter set to continuity. With it, you have to check both ends, on both cables - which display pin corresponds to which motherboard one. The tricky part is for the inverter, especially if they have different number of pins. It would be hard to guess which is which, and if it's not here, you are mostly out of luck. You can try to google the inverter's model number and hope that somewhere you'll find the pin-out, but the chances are slim.

There is an easy way as well - just run it on single lamp

Whatever you choose - Good luck!

 

Until now I've not received the new computer, so I'll check that when I'll get it.

 

OK I come back with more infos:

here is the inverter for X500-102 (1xCCFL):


and the other one for the X500-14D (2xCCFL for a full HD LCD)


Just below the mobo connector for the 102:


and the other one for the 14D:


maybe you can't clearly see, but there are more wires for the double CCFL (that's logical).

There is no FullHD version of the X500-102 in my country, but here is an equivalent in the USA:
TOSHIBA Qosmio X505-Q8104X Notebook Intel Core i7 2630QM (2.00GHz) 8GB Memory 1TB HDD NVIDIA GeForce GTX 460M 18.4" - Newegg.com

and the same Sandybridge platform with a 1680x945 resolution:
TOSHIBA Qosmio X505-Q8102X Notebook Intel Core i7 2630QM (2.00GHz) 6GB Memory 640GB HDD NVIDIA GeForce GTX 460M 18.4" - Newegg.com

I've searched on SparePartsWarehouse.com for the mobo reference and they are the same.
So for me there are only the inverter, the LCD and the cable which are different between the 2 Qosmio.

So for me I've just to put the FullHD "package" (LCD+inverter+cable) on the nonHD computer.... what do you think ?

 

If you are 100% sure that the MoBos are the same, then go ahead. Just for the peace of mind it would have been nice to check the cables with multimeter, as I already explained.

 

I've used their unique ID "PQX34U-xxxxx" and each time I got the same result.
The only difference for me is that the X500-14D is older (with a Core I7 720QM) than the new Sandybridge version (X500-102 with 2630QM). But on the mobo, physically the difference is minimal: no connector for the bluetooth module (no more bluetooth module on the top cover) with the sandybridge platform and different chipset of course. Except that, the design is strictly the same.
In the technician manual, they say that we must flash the EC/KBC bios when changing the LCD. This part of the BIOS is integrated in the BIOS distributed by Toshiba, so I hope I'll just have to flash the last version to update everything. If I'm crashing something I've found a procedure to flash the Phoenix BIOS by booting on an USB disk.

 

So I've put the FullHD "package" (LCD+inverter+cable) on the X500-102 and everything works like a charm until now. I've just flashed the BIOS to v1.9 in order to update the EC/KBC part. I'm really happy it works, thanks a lot Triturbo for your support !

 

No problem. Glad that it was straight swap and no modifications were needed (and nothing fried as well )

 

View attachment 114700

Hi!

I have an error on my new laptop screen, after I changed it. Old one is 1366x768 panel, and the new is 1600x900. I attached a picture about the error. I didn't not changed the cable yet. Can this be the reason?

Thanks!