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Linux - Laptop and Netbook Having a problem installing or configuring Linux on your laptop? Need help running Linux on your netbook? This forum is for you. This forum is for any topics relating to Linux and either traditional laptops or netbooks (such as the Asus EEE PC, Everex CloudBook or MSI Wind).

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Old 03-03-2007, 10:47 PM   #1
General
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What hardware component determines refresh rate in laptop?


Refresh rates below 75 Hz cause me serious problems. I am currently pricing older laptops and the refresh rate is a deciding factor in my purchase. I have managed to dig up archived user manuals for the laptops, but they don't say what refresh rates they run at...and I searched Google up and down for this information. With slow research, I have been able to determine some of the hardware components used in the laptops. Too speed up my search, I wish to know which hardware components are directly related to defining a laptop's refresh rate. That way, theoretically, I can dig up drivers and manuals for the specific components, and from that hopefully I will be able to learn the supported refresh rate of each laptop.
 
Old 03-04-2007, 02:33 AM   #2
Simon Bridge
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Woops - double post

Last edited by Simon Bridge; 03-04-2007 at 02:36 AM.
 
Old 03-04-2007, 02:36 AM   #3
Simon Bridge
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The refresh rate is a dummy parameter for LCD screens with a digital interface - each dot is just told to switch to a particular state and then stays there until told otherwise. Laptops screens use a digital interface (why put an analog vga hardware in only to do A to D on the same board?) - but I don't know about the really old ones.

The analog (VGA) interface screens are scanned in the same manner as CRT screens: one dot at a time.

The refresh rate, together with the resolution depends on how fast dots can be written to the screen. This depends on the dot clock and the A to D converter used for the screen. The actual physics of the screen will be a factor too - how quickly one can alter the charge on a given zone, relaxation times etc.

You can get faster refresh rates only by lowering the resolution. 50-75Hz is normal, even for quite old laptops. But remember: the farther back you go the lower the expected resolution.

So what are these "serious problems"?

Last edited by Simon Bridge; 03-04-2007 at 02:39 AM.
 
Old 03-04-2007, 03:56 AM   #4
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Quote:
Originally Posted by Simon Bridge
So what are these "serious problems"?
Well, after about 5 minutes: headache, blurred vision, etc. At least that is what happens with my CRT monitor on my desktop computer at below 75 hz.

I have never owned, let alone used a laptop before. The laptops I am looking at use a LCD, according to their user guides. Models are from 2000 and 2001. Based on your description of how LCD works, maybe I don't have to worry...?

Last edited by General; 03-04-2007 at 03:59 AM.
 
Old 03-04-2007, 02:53 PM   #5
Simon Bridge
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Have you been tested for epilepsy?

A CRT can get a subliminal flicker at low refresh rates due to the screen redrawing itself 60 times a second (or so). CRTs must be run at quite high refresh rates as a result, and they are built for it. (Do you get headaches from motion picture flicker - 48Hz - or flourescent lights - 50-100Hz - though CRTs are particularly prone to this effect: you can alleviate it somewhat by adjusting the colours.)

A 21st century lappy should be using a digital interface - no flicker. If you want to see the effect, go to a store and look at the display models, they will all be running less than 75Hz. See if you still get a headache.

I remember having similar concerns myself. It took but a moment to determine they were unfounded.

Last edited by Simon Bridge; 03-04-2007 at 02:59 PM.
 
Old 03-07-2007, 01:56 PM   #6
SilverBear2006
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Eyes & DFTs

I have to agee with Simon on this, 100%

I used to use a 19" CRT graphics monitor that I really liked --back when 15" was the standard. I judged that my aging eyes were worth it.

After I got a laptop, I was totally blown away with how much easier on the eyes [yeah, less headaches, too!] a Digital Flat Panel is.

I have replaced my 19" CRT with a 19" DFP, and it is great. A Samsung SyncMaster 940BW, just for the record.

120x120 dpi resolution. No flicker. I can get as close to it as I want --usually 22-24 inches [56-61cm] is good for reading text. But I can lean back in my chair to about 32" [82cm] and it still looks nice and sharp.

The problem with the CRTs is that there is electron gun aimed right for your head, and it is beaming a flickering horizontal and vertical scanning pattern at you. If you have a video camcorder [analog] with autofocus & auto-exposure, shoot video of a computer CRT screen. On the tape replay [on a good television or monitor] you will see the actual scan lines and flicker on that computer CRT screen, under certain zoom & lighting conditions.

Your eyes will still get tired if you strain them --just like reading a book for too long. But the effects you are describing will be much less frequent --or gone entirely.

2 things to remember though:
Older laptops from 2000 & 2001 did not have nearly as good screen & video drivers as they make these days. My laptop was purchased in 2004, and it was fine.

The other thing to remember is that video RAM has gotten much cheaper since 2001. Modern graphics controllers are in the 128 - 512 MB range for video RAM. My 2004 has 64MB. A 2001 machine would be lucky to have 32MB of video RAM --that's what many desktop graphics cards were still using [in cheaper machines] back then. It might have only 16MB VRAM. That is going to limit your ability to watch streaming video online, or watch DVDs or VCDs on your laptop, especially since the system RAM is probably going to be 128-256 MB in a laptop that old. And a slow, hot CPU. . . you will be disappointed in the performance, even running Linux.

------------------------------------
The laptop manufacturer is still going to publish frequency rates and color depth figures, even though the physics behind them is different for CRTs and DFPs, as Simon explained.

The direct answer to your question is that in a laptop, you have the video card/chip which has a certain capability, but then, you also have the screen panel -which will probably have a lower capability.

My laptop's video AGP graphics controller is capable of pushing a resolution of 2048x1536 at 16 or 32 bits color depth. Theoretically. But the screen that Toshiba put on the machine can only handle 1280x800 at 16 bit color depth, maximum.

So it's those two factors, the graphics controller plus the screen, that determine what you get.
-------------------------------------

My advice is unless you're getting it for like $50, don't waste your money on an older laptop. Laptops are expensive --or impossible-- to upgrade, unlike a desktop machine. I build & upgrade desktop computers, so I know whereof I speak, on this point.

You might want to try getting a flat panel monitor for your desktop computer. A good 17" can be had for under $200 US. Get one that has both a VGA and a DVI connector. You can always upgrade your desktop video card to one that will do a DVI interface, probably for $30-40.

Ask at the MepisLovers.org hardware forum if you need or want any more info. I'm over there more than I'm here. On second thought, I can get email notification if you post to this thread, so that will work.

Bottom line: I hear you, brother. We each have only one set of eyes. And they're even harder to upgrade than a laptop!

--SilverBear

Last edited by SilverBear2006; 03-07-2007 at 02:00 PM.
 
  


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