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LCD monitors and RISC OS

By Chris Williams. Published: 14th Mar 2004, 23:28:45 | Permalink | Printable

Shopping for TFT?

LCD motifMini-guide Ages ago, a reader asked drobe.co.uk to write an article about LCD monitors and RISC OS, because he wanted to buy one and wondered how to choose one. The simple answer is: ask a dealer. This is basically because they're likely to be selling LCD monitors that they've tested with RISC OS and have appropriate Monitor Definition Files (MDFs) to drive the flat screen monitors. We've pestered a few dealers (see links at the end) for information and compiled a straight forward guide to LCD monitors with RISC OS for those of you who want to go it alone or are just interested.

Firstly, why all the fuss about LCDs? Although they're reducing in price from month to month, TFT monitor supply will reportedly struggle to match demand in 2004, which may slow further price reductions. LCD monitors work by using a fine grid of pixels and also use less energy than CRT monitors. Their thin design means they use less space than CRT monitors and weigh much less too. Generally, LCD monitors have a sharper image that's flicker free, which is nicer to work with. CRT monitors, on the other hand, are cheaper and so higher resolutions can be afforded. CRTs also 'react' faster to changes in the displayed image, whereas LCDs tend to update slower (response time is generally in the order of tens of milliseconds).

MDFs
A Monitor Definition File defines the characteristics of a display and the various resolutions it can handle. RISC OS needs an MDF to tell it how best to use a monitor without damaging it, although modern LCD monitors will refuse to display a resolution that it can't handle. Fortunately, there's various ways to find a suitable MDF. You can generate your own using Acorn's MakeModes software provided you're competent with MakeModes and aware of your monitor's specification. Alternatively, you can have your supplier produce an MDF for you if possible. Another method is to use an existing MDF file for a CRT monitor that matches the resolutions provided by your LCD monitor. For example, my RiscPC's 15" LCD monitor works well with the MDF for the Iiyama Vision Master Pro 450. Modern LCD monitors also have an 'auto-adjust' button or on-screen menu option that automatically adjusts the monitor to match the computer's video output, which helps. You can find a load of MDFs from here. However, for top end screen resolutions, a properly defined MDF is preferred. Additionally, the software with the Viewfinder graphics card can generate a suitable MDF for a monitor if you can provide the monitor's specifications.

Another tip, if you're having trouble, is to change *configure sync to 0 or 1, if the 'auto' setting doesn't work.

"We supply a custom designed MDF with each of our LCDs," explained CJEMicros' Chris Evans. "Some monitors (LCD or CRT) will not display until an MDF is loaded. I made a newsgroup posting about it some time ago [with the] subject 'when is Mode 27 not the same as Mode 27'."

Calibration
The setup of an LCD monitor can be a fiddly process but there is help as Peter Gaunt's Zebra software can be used to calibrate an LCD monitor. While Zebra displays a test pattern, the LCD monitor's previously mentioned 'auto-adjust' feature can be activated. The monitor will then use the test pattern to ensure the display's positioning, colour balance and synchronisation timings are spot on.

RiscPC and LCD monitorResolution
Check the maximum resolution of the LCD monitor before purchase to make sure you're truly happy with it. I personally use my RiscPC in 1024x768 in 32K colours at 70Hz on a 15" TFT monitor (pictured), which is possible with the RiscPC's 2MB VRAM although that might be woefully tiny for some users. Obviously if you're using a RISC OS computer that provides much greater resolutions (namely a Viewfinder, Omega, Iyonix or otherwise), you'll probably want a monitor that can take advantage of large desktops and high refresh rates available to you - LCD monitors capable of 1600x1200 aren't exactly cheap. Also, be aware that some larger LCD monitors have a maximum resolution of 1280x1024, which is an X:Y aspect ratio of 5:4. Screen resolutions of 800x600 and 1024x768 have a ratio of 4:3 and displaying them on a 5:4 screen will result in a stretched image, unless the LCD monitor provides the ability to control this scaling.

Pixel defects
Due to their inherent complexity, LCD monitors aren't perfect and there's a chance there may be a few defective pixels on the screen. If you're lucky you won't notice any, but once you do, you usually can't help but be distracted by them. Different manufacturers and suppliers will have different pixel defect tolerances, which defines how many defective pixels a monitor can have before it can be returned for a replacement unit - check this tolerance before purchase.

Connections
LCD monitors use standard 15-pin VGA video connectors. Paul Richardson of Explan also commented: "There is a better RISC OS video output system developed by Pace engineers, which would operate with DVI graphics cards. I assume this design work has passed to Castle along with the rest of RISC OS, since any work by Pace engineers had to be added back into the source-pool. However, it's possible that Castle don't realise what they've got, or are unaware of how important this code is for the future types of digitally-driven monitors."

Links


CJEMicros, Liquid Silicon, Explan websites - dealers who know a thing or two about LCD monitors and RISC OS
Also, LCD pros and cons and how to pick an LCD How TFT LCD monitors work

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Next: Omega MIDI, ethernet progress

Discussion

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Would Castle comment on where they are with DVI?

 is a RISC OS Userjonix on 15/3/04 10:50AM
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Just read this week - sorry can't just remember werre just now - that LCDs with DVI connection could go up in price by 14%.

This is because with DVI in they may be reclassed as 'being suitable for TV display' and therefore be liable to the extra tax.

This is why DVideo had DVI out but not DVI in - to escape the extra tax.

Dave C

 is a RISC OS UserDaveC on 15/3/04 2:51PM
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The problem Castle faces is simply to find a suitable PCI graphics card with DVI. If it isn't a GeForce2 based card, a new video driver would have to be written - so it would be best to find a GeForce2 based card with DVI output, which is even more difficult. Apart from that, I can't think of any problem with DVI that Castle/RISC OS 5 faces. After all, DVI is AFAIK totally transparent to the driver - basically, you just select the DVI output instead of the analogue.

Steffen

 is a RISC OS Userhubersn on 15/3/04 3:16PM
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Seemed to remember Jack L talking about this at SW Show and I think that it also revolves around the issue with the different colour mappings between Windross and RISCOS i.e RGB -BRG or something similar. In an analogue card they can just change wires around but for DVI this would need a DVI output mapping module.

 is a RISC OS Userbluenose on 15/3/04 10:39PM
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17" LCDs are the best price-point at the moment. They're not significantly more expensive than 15" LCDs on the one hand, but they provide much larger working areas. Then again, those of us with poor eyesight may find LCDs a struggle; they're only really usable on their native resolution, and often the native resolution has everything being quite tiny. Look for an LCD with a lower response time, 16ms or lower is fine. Mine is at 75Hz at the moment. Many LCDs have both DVI and analogue in, but not all.

Hubersn: Geforce 2 based cards are the absolute bottom of the barrel as far as PC video cards go, Castle will find them increasingly different to source sooner or later. Geforce FX and Radeon 9200 based PCI cards do have DVI, however they cost 1.5 to 2 times as much as the Geforce cards, and I doubt Castle is going to want to slash that much off their profit margin. Would it not be possible for RISC OS programmers to port their own driver for the FX or Radeon or Matrox PCI cards from Xfree? It isn't onboard video, you can physically replace the thing :)

 is a RISC OS UserClades on 16/3/04 2:48AM
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Must say that we haven't noticed a drop "from month to month" in LCD prices. More like a 25% price hike in December, with 15" units in constraint through until quite recently. It's all the fault of that <a href="[link]">Linda Barker</a> woman...

 is a RISC OS Usermikeg on 16/3/04 7:21AM
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Clades: No, "bottom of the barrel" for PC video cards are the ATI PCI 8MB ones, strictly speaking.

No, porting a new driver has too many technical and practical challenges that don't make sense for a non-OS developer to solve for RISC OS.

 is a RISC OS Usermrchocky on 16/3/04 11:36AM
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I don't know why you say this, because 8mb PCI cards were low-end for PCs a full five years ago. Even 64mb video cards are on the way out now. 32mb is fine to drive any monitor, anyway.

 is a RISC OS UserClades on 16/3/04 11:44AM
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I say this because they are still available (I have one here purchased a few months ago), and your phrase was "bottom of the barrel". Their use in PCs 5 years ago isn't particularly relevant.

 is a RISC OS Usermrchocky on 16/3/04 11:52AM
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8mb video cards are still available in the same sense that K6s are "still available" - they're ancient stock that wasn't sold at the time, they're not being produced, and you can buy them second hand for less than the cost of a couple of hamburgers. I doubt there're many cards with less than 128mb of ram still being actively fabbed today, if any.

 is a RISC OS UserClades on 16/3/04 10:57PM
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Clades> That's blatently total utter nonsense. Give up.

 is a RISC OS Userimj on 16/3/04 11:54PM
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What I would like to see, is where there are widescreen MDF for RISC OS, due to having a 15" 16:9 ratio, does get a little tedious having RISC OS stretched.

Personally I have no trouble with my Radion 9600 ATI card in my pv, with its DVI out

 is a RISC OS Userem2ac on 17/3/04 9:40AM
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em2ac: have you tried using MakeModes? You can get it from acorn.riscos.com IIRC but using Google should tell you many places to get it. It does require a lot of fiddling, but you can make some useful modes (like the one I'm using now, 1280x1024x72Hz :)

 is a RISC OS Userjohn on 17/3/04 10:51AM
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em2ac> It's pretty easy. I made a lovely 1280x800 mode for use on my widescreen Sony VAIO (running VirtualAcorn). MakeModes or CustomRPC will do the job.

 is a RISC OS Userimj on 17/3/04 3:55PM
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Tried Make Modes, but I have no idea on how to actually make a new resolution, just modify the current ones.

Dont suppose I could have a copy (or the text dumps of the modes) of your(s) :-D

this Uni degree is taking a lot of my time up, oh well off to the SU for St Drinking day! :-P

 is a RISC OS Userem2ac on 17/3/04 5:40PM
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Guess that's a no then :(

 is a RISC OS Userem2ac on 19/3/04 1:48PM
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em2ac: I don't (yet!) have an LCD monitor to help you out with makemodes files I'm afraid, but there is a manual online here:

[link]

I haven't read it myself, but maybe it'll explain how to create the modes you want?

 is a RISC OS Userflypig on 19/3/04 2:49PM
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Cheers, that has helped a little, but it still restricts me to the bog standard resolutions, any ideas?

 is a RISC OS Userem2ac on 19/3/04 6:03PM
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Scratch that, have just managed to copy & paste from my Dad's Virtual Risc PC one :D now i have Widescreen on my RPC

 is a RISC OS Userem2ac on 19/3/04 6:16PM
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em2ac: Well done :)

Just for reference, I had a quick go with MakeModes, and to change the resolution, it looks like you need to go to the right hand side, under "Mode Timings". The two numbers in the "Display" row represent the X and Y resolutions respectively, so you can change these to make new resolutions. It's useful to change the name as well, otherwise it can get very confusing ;)

 is a RISC OS Userflypig on 19/3/04 6:42PM
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lol i c it now, feel like a right dunce! hehe thanx again

 is a RISC OS Userem2ac on 19/3/04 9:48PM
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No probs. I imagine you were still recovering from Wednesday night :guinness: :)

 is a RISC OS Userflypig on 19/3/04 10:51PM
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It's interesting that you comment on cards not easily sourced with 8Mb (or even 16-64Mb). What about the simple fact that their PCI? PCI graphics cards are obselete - you will not find any newly produced PC motherboards without an APG slot, and most of these are 4x now too. Castle really should have gone with APG in the first place, as the cards are more widely available and also cheaper. They're also fast, which is why APG is so popular for PCs. I haven't seen any PCI graphics cards on sale fora very long time, apart from RISC OS dealers and second hand stalls at computer fairs.

 is a RISC OS UserSmiler on 9/4/04 12:01PM
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No, this has already been discussed in detail in many places, including their website. AGP would have done nothing for the graphics performance of the Iyonix, due to the effectively integrated NorthBridge. AGP would have added to the cost and complexity of the Iyonix, and would have made it later.

PCI cards are clearly still available, as demonstrated by Castle still putting them in machines. For how long though, I don't know.

 is a RISC OS Usermrchocky on 9/4/04 12:29PM
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AGP is also on its way out, it is being replaced by a new version of PCI

 is a RISC OS Userskock on 9/4/04 1:23PM
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