ARM Based microATX Board
Pages: 1 2
Glen Walker (2585) 469 posts |
I didn’t want to put this in “porting” because I’m not sure it would ever be viable…but for anyone who wants to run something else on an ARM cpu this could be an interesting choice. |
Steffen Huber (91) 1953 posts |
The unexpected return of analogue video output in modern systems :-) |
Rick Murray (539) 13850 posts |
Want to back that up with some sort of evidence? Let’s look at this. Video signals are created digitally. These are then converted to analogue to be sent down a cable. When these signals reach the monitor, if it is a flat panel type, the signals are converted back to digital in order to be processed for the display. Secondly, let’s look at the signals themselves. VGA RGB signals are analogue, carrying colour information as 255 possible steps in a range from 0V (black) to 0.7V (full intensity). That means each increment is a difference of 0.0027V. Analogue video is susceptible to degradation, from cable lengths, socket contact issues, RFI, and so on. Higher clearer resolutions? Seriously? 4K video is either 4096×2160 (TV/movie) or 3840×2160 (UHD, keeping with 16:9 ratio). In order to support a resolution such as that with analogue VGA, you’d need an ADC running at about 530MHz just to refresh at 60Hz. To put that in comparison, VGA has a theoretical bandwidth of 388MHz (which corresponds to 2048×1536(QXGA) at 85Hz), though in reality many domestic VGA devices start to suffer beyond about 160-180MHz (FullHD (1080p) is about 150MHz). Once you start to go beyond that, you’ll be hit by physics and the properties of wiggling a wire at extremely high frequencies, and you will start to see ghosting effects, shimmering around contrast (like text), etc. So for a decent analogue signal, it’s probably safe to peg the maximum useful bandwidth of VGA at about half of its theoretical – in other words, around 160MHz or so. Oh, and not only would you need a ~530MHz ADC, you’d need a corresponding DAC, plus a damn good cable between the two. Wouldn’t it make more sense to connect a digital device to a digital device using a digital pathway, and leave analogue for legacy equipment? |
Steve Pampling (1551) 8172 posts |
Seriously? You’re using the requirement of a processor at the video display as an argument against digital?
Yup, R-2R ladder circuit works as a DAC but there are frequency limits. However, all things considered, colour displays are a set of dots1 so you’re into addressing points in a matrix. You’ve gone digital. 1 Ye olde colour CRT (the ones that replaced black&white back in my schooldays) had different colour phosphor dots close together but with a magnifying glass the arrangement was very obvious. Mind you in those days we’d just press our noses close and squint at the rgb triangle arrangement. |
Rick Murray (539) 13850 posts |
Model number? I’m having difficulty believing an analogue HXGA monitor exists.
Google it. QXGA is about the best you’re going to get from analogue.
Ditto most of the larger analogue monitors. From background signal processing to correction for things like pincushioning available from a front panel control… the later batch of monitors had quite a bit of digital circuitry inside.
Hehe. Unless you’re using a 14" CRT from the ‘90s, there quite likely is an unseen computer inside your monitor. And there’s one in your harddisc. One in your SD card. One in your network controller. One in…….you get the point.
As are our eyes. However the panel itself is treated as an array of X by Y dots so it is suitable for being handled almost entirely in the digital domain.
Are you saying CRTs took less power?
Most typical displays worked at around 60Hz and people often got headaches from them. We are accustomed to looking at CRTs so might not realise how much they flicker. My eyes are sensitive to it, so it was easy for me to understand the flicker issue by simply turning my display upside down. Other people may vary. TV runs slower (50Hz) but the flicker is less as TVs tend to have phosphors with really long decay times, so much that a moving light source on black (pong?) can leave a notable trail behind it. 85Hz and the like tended to be used by DTP/graphics professionals who need rock solid displays that they state at, and by gamers searching for the best most fluid video.
A person who claims to be able to make a 1GHz DAC out of discrete components (sorry, I flat out don’t believe that) should be aware that different frequencies propagate at different rates. Analogue is a bazillion different and rapidly changing frequencies with extremely subtle differences. Digital is a fixed frequency series of on or off signals with the benefit that in normal cases you know the receiver will get an exact copy of the source signal. |
Steve Pampling (1551) 8172 posts |
We may have crossed mails as that was rather the point I was making too.
As you say the data is either there or not and when a verified byte of data arrives it’s value is always exactly what was sent. 1 The R-2R ladder DAC construction needs precise resistor values to produce an accurate colour. |
Malcolm Hussain-Gambles (1596) 811 posts |
Well I ran a linux system that had a resolution of…. Talking about refresh, I always like the fact that even though the eyes/brain work at 20-30Hz, 100Hz is smoother. @DavidS – Isn’t everything an analogue device that uses a voltage? |
Rick Murray (539) 13850 posts |
That’s why HDMI has differential pairs. External interference will affect both wires in the same way, so it’s a simple thing to recover the intended bit. |
Dave Higton (1515) 3534 posts |
But have you looked at the glitch that occurs at half scale? There are two problems that must be solved if there is to be no glitch: 1. The rising and falling edges don’t occur at the same speed. This is because the P-channel and N-channel devices have different capacitances and speeds, which is in turn down to the different carrier mobilities of P and N type semiconductors. 2. You would want the rising and falling edges to be exact mirror images of each other. Even if the rise and fall times were the same (which they never can be), the shapes will never be perfect complements. So there will always be disturbances on transitions. But here’s the big difference: in an analogue transmission system between computer and monitor, the monitor doesn’t know what’s glitch and what’s a settled value; it has to try to display it all. Contrast that with a digital LCD monitor, which knows when the transitions are, and can wait that settling time before the signal is gated into the pixel in the panel. In practice, I’ve seen some commendably good displays on analogue monitors, but I’ve seen far more where the transitions are indistinct and there has been a faint ghost. You have to have everything just right, and it rarely is. On the other hand, I’ve never seen a display on a digital monitor that isn’t superbly crisp. Ghosts simply never happen. I would not want to go back to an analogue monitor now. |
Clive Semmens (2335) 3276 posts |
Nor me neither. Here I am sitting at a digital 4K 43" monitor, pin sharp, that cost under £300. I don’t know if there ever were analog monitors with that resolution – if there were, they certainly weren’t affordable beasts. (Quite apart from the fact that they’d have weighed a ton.) |
Rick Murray (539) 13850 posts |
;-) My monitors are “older”. A Flatron L192WS (1440×900 – PC) and a iiSonic something or other (1280×1024 – RISC OS). They are both digitally controlled LCDs. With only analogue inputs. <facepalm> Still, the video hardware is reasonable, I don’t drive ‘em too hard, the cables are good, and there’s little interference that isn’t being caused by the monitor or the computer(s). So the pictures look okay. Moreso with video, where MPEG4 compression artefacts are more of an issue than monitor signal quality… |
Rick Murray (539) 13850 posts |
That won’t help with compression artefacts. :-) |
Dave Higton (1515) 3534 posts |
Wow. I thought all those problems were over and done with 20 years or more ago, when the FCC regulations and their Euronorm equivalents came into force. I have never, ever, seen the problems you describe. I can only assume that some of the stuff you have is faulty. Maybe you’ve got stuff that falsely claims to conform to FCC regs.
Sorry, my friend, they’re taken :-) But there’s nothing special about them. All digital monitors behave like that (with the possible exception of yours). I can understand that, with your pleas of poverty, you’re not going to be able to replace them any time soon, and I feel sad for you. Since this is Aldershot, I feel obliged to point out that the interference problems that we used to experience in the UK 30 or 40 years ago have ceased because of the action taken by the EU. They made it mandatory for products sold in the EU to conform with a very sensible and well thought out set of standards. I remember the howls of protest from manufacturers in this country when faced with the increased costs of conformance testing. I can’t believe that a UK government (of any hue) would have taken on the business community. Nowadays, of course, manufacturers are used to it – the sky didn’t fall in – and stuff Just Works. The same applies for safety – in the USA, Underwriters Labs had done a great job with UL1950, which was taken on by the rest of the world variously as IEC950 and EN60950. So stuff Just Works and people don’t get killed. But because there aren’t problems, ordinary people don’t notice. So it’s one of the many examples of “What did the Romans ever do for us” as applied to the EU, and one of the many reasons why I feel desperately disappointed to be leaving its benign influence. Anyone else here noticed how the UK government is dragging its heels in comforming to EU pollution directives? It’s cheaper to let people die, of course. Not that I’m cynical about the UK government and those unelected bureaucrats in Whitehall, you understand. |
Rick Murray (539) 13850 posts |
As this is Aldershot…
Oh, you must mean the dictator known as Theresa May – what else do you call a person who just assured the EU that Brexit is going to go ahead, after a legal challenge reminded everybody that the UK is, in fact, supposed to be a parliamentary democracy (in other words, the MPs vote). This unhinged undemocratic dictatorship, of course, receiving full support from the anti-EU gutter press, and the pro-democracy judges (and the woman who brought the challenge) receiving death threats and worse. This, I guess, is what “the will of the people” and “taking back control” must mean. Some have drawn parallels between letting the MPs vote (as has always been the law of the UK since law was passed from royalty to parliament) as acts of treason, acts akin to Mugabe’s Zimbabwe… clearly it is must better instead of reasoned logic to just have an executive that does whatever the hell she pleases. We are a long way from the days of “I’m the Queen, I win”, but apparently the law is an annoying inconvenience when it comes to a once-great country shooting itself in the foot. Repeatedly. And to compare a proper vote with Mugabe while an executive ignoring the lawmaking process is fine…? I thought most Brexiteers were retards, but what? Seriously, what the effing eff? The more this goes on, the more I am beginning to view the (not so) United Kingdom as “foreign”. |
Chris Mahoney (1684) 2165 posts |
That certainly doesn’t sound right. My biggest digital display is in my home theatre and has a very low resolution for the size – the individual pixels are clearly visible when close to the screen. If I display a still frame, I can inspect any block of pixels at random and see absolutely no flicker, no colour change, no distortion… A digital system will typically either work or not work; it is very rare for there to be a middle ground, and in almost all cases that middle ground can be eliminated. The last time I ran into problems was when I bought a cheap audio cable and the sound would completely drop out at points (ie. alternating between “working” and “not working”). I replaced the cable with one from an actual AV shop instead of a generic electronics shop, and have had no problems since. |
Steve Fryatt (216) 2105 posts |
I know this is Aldershot, but are you sure about that bit? The Mugabe references that I’ve seen reported are people comparing the press reaction to the High Court judgement with the great man, not the desire to determine whether Parliament gets a say in things. That said, there is a rather nice irony that in the selfless pursuit of regaining Parliament’s sovereignty, we’re1 apparently more than willing to overrule its sovereignty in order to achieve the goal that a whopping 27% of the population voted for… An irony that seems to go over the heads of most Brexiteers, unfortunately. 1 That’s “we’re” in the sense of the Daily Mail and Daily Express, along with some Twitter and Facebook users too stupid to be able to tell an “ethical investment manager” apart from a US sports journalist. |
Steve Pampling (1551) 8172 posts |
You’re right Steve, the Mugabe reference was to the disagreement between the judges and the dictator (with weakened power,fortunately for them) with the judges in the right as far as everyone except Mugabe was concerned.
Anything other than mob rule1 and very short words is likely to go over the heads of the mail and express journo’s and probably the readers2. The operative fact is that it took an Act of Parliament to alter the rights of the UK public when the referendum took the UK in to the EU and under long standing law it is Parliament that must amend the legislation that alters or affects the rights currently in place. Of course if you’re talking about legality, rights or proper process you’re likely to use words that are too long or complicated for the print decorated litter tray liners 1 They shout loud to drown out logic, reason and truth |
Andrew Daniel (376) 76 posts |
The UK was not taken into the EEC by a referendum but by Edward Heath’s Conservative government. The previous referendum was called by Harold Wilson as the Labour party had deep divisions on the matter. |
Steve Pampling (1551) 8172 posts |
A number of entry attempts were blocked by De Gaulle in the 1960’s but De Gaulle resigned in 1969 and in 1973 the UK applied again and was admitted. It took an Act of Parliament to change the rights of the UK public, any attempt to change those rights without reference to parliament would be illegal. 1 The views may or may not match the result of the recent referendum. The public can be fickle2 at times. |
Steve Fryatt (216) 2105 posts |
The real problem with the referendum is that no-one has a clue what “leave” actually means… Do 17.5m people want a “hard” Brexit where we cut all ties with the single market and wave goodbye to a large chunk of UK industry, research and academia, or do some of them prefer a “soft” option? Would some of the 17.5m feel differently once they’ve got a better idea of what it will actually mean for them and their families, friends, colleagues, etc? The referendum was so badly conceived that all we actually know was that 16.1m people want to stay in the EU, 17.5m want to end that membership and replace it with something else from somewhere on the wide “leave” spectrum, 13m didn’t care enough to tell us what they think, and almost 18m weren’t asked for their opinion. That’s what Parliament now needs to work out, and quickly, via the usual democratic processes — it’s not just a matter for Davies, Fox, Johnson and May to sort out according to their own satisfaction. And ideally it needs working out quickly, before anyone thinks about invoking Article 50… |
Malcolm Hussain-Gambles (1596) 811 posts |
What no-one wants to accept, is the fact that you cannot “work out” what will be in the negotiations until you negotiate. There seems to be some blind belief that we can decide on what are negotiations are then the EU will agree. The referendum wasn’t badly concieved it was very clear. The EU (as an institution) was very clear, they were totally unwilling to have any communication with the UK about any of it’s concerns – hence why it ended the way it did. Leave means leaving the EU, nothing more, nothing less. Another question, if we had a general election and people voted for Labour, would it be OK for parliment to vote on whether they get to govern. The Act of Parliament to alter the rights is one thing, invoking Article 50 doesn’t alter anything. Asking would people change their vote if they know what it means, is like asking what the world will be like in 500 years time. The reality is that know-one actually knows what the effect will be until the negotiations finish. There are a people who think that delaying is a good idea – one thing that will stuff the economy is uncertainty. |
Steffen Huber (91) 1953 posts |
If this is “the real problem”, this whole democracy thing seems to be full of problems. After all, who can say for sure what “the voter” really wants? Different people want different things. Unless you provide a million different things to vote for in a referendum (or, more generally, an election), you will always have this problem. |
Rick Murray (539) 13850 posts |
Pray tell, what exactly is this “soft Brexit” that you speak of? It seems to me to be a rather airy-fairy way to remain a part of “Europe” by either: In truth, everything is intertwined, so the choices are going to be “take it or leave it”. Britain doesn’t “make stuff” any more, a lot of what is made is using imported parts. There is no hard reason why companies cannot just relocate the work elsewhere in Europe. The banking? Well, one might want to read up on WTO trade and banking “services”. Leaving won’t be kind to the banks.
It was extremely badly conceived. The actual question was simple: EU leave or stay? But all of the questions and bull surrounding it were unclear. To clamp down on immigration (UKIP’s one trick pony), one doesn’t leave the EU. One must leave the EEA. That’s an entirely different thing and it will be damaging.
If you believe that, you don’t quite understand the nuances of the various European establishments. Norway is not a member of the EU. It is a member of the EEA. Thus, it partakes in the four freedoms. Leaving the EU won’t change that. “The will of the people” generally understands leaving the EU to give them the right to kick out foreigners and to pour loads of non-existing cash into the NHS. Leaving the EU won’t necessarily make that happen. Leaving the EEA will. But is that a place you really want to go? Let’s put it like this. The world operates as a global economy now. The main players are the US (through might and bloody mindedness) and China. Please explain to me how the UK, as a smallish island, is expected to have any strength at all in international negotiations? Not only are you about to have the history of telling your nearest trading partners to sod off, you’re also using a currency unique to yourself, and – to be quite blunt – in the context of the world, you just aren’t important. As a part of the EU, you benefit from negotiations with the EU as a whole. On your own? Sure, you can enter into negotiations with whatever country you please. Just don’t kid yourself that it won’t be them dictating the terms. You, alone in the world, a population of ~64 million… That’s less than the population of Egypt or Germany, about a third of the population of Russia, about a twentieth of the population of the US, and don’t even compare it to China… Out of the EEA the UK’s negotiation abilities will be weak. In the EEA, the UK will be expected to accept freedom of movement in addition to the other freedoms. One must think long and hard about the practicalities of simply “leaving the EU” (what the referendum actually asked) with jacking in access and rights to Europe entirely (what a lot of Brexiteers imagine the referendum to have meant). Back to your supposed soft Brexit. It’s clear that on a slim majority (not the “clear and overwhelming” that is oft repeated in the media) of those who bothered to vote and were eligible to vote (which was only slightly over a third of the electorate), the unelected government in power to the moment – May and the Three Brexiteers – want to drag the country out of the EU. And in doing so, likely out of most of the European institutions in order to control immigration etc. Now reread to above and ask yourself – if this is going to come to pass, why does anybody in the UK think the UK is going to have a strong hand here? What May is asking is something that runs counter to the founding principle of the EU (and EEA). If the UK gets access to three freedoms but can refuse immigration, other countries will want that. It’s simply not viable, nor is it even remotely fair on the rest of the EU. Europe will tell the UK to get stuffed. Because… as an outsider, the UK just isn’t that important. That’s what Leave is meaning. So we have Farage on the box and the screaming idiots doing their best to come up with easy to remember slogans to avoid the people realising how hard they’re about to get shafted. Oh, and did you notice in the middle of this IDS wants to do away with the triple lock pension because waffle waffle oh look Brexit! |
Malcolm Hussain-Gambles (1596) 811 posts |
1. Any way of describing an exit of the EU is going to be vague. It’s not my Soft or Hard Brext, it’s a term that’s been brandished about. Anyone who thinks we can dictate to the EU is having a laugh, but there again anyone who thinks the EU wants to self destruct is also having a laugh. The triple lock was an insanely bad idea, but I don’t think they are going to squirm out of it easily. |
Rick Murray (539) 13850 posts |
This is why Scotland’s IndyRef failed. A plan but no idea how to get there. Wouldn’t one imagine that breaking from the EU should have some sort of definite idea about how to achieve it, and more specifically if it is even a viable idea. Ignore the screamies predicting the demise of the EU, they’ve been saying that for a decade…
It imports more than it exports, but that is today. Things might be quite different when there are import/export tariffs and other EU countries realise it is cheaper to produce within the EU.
The UK makes things – like pieces for Airbus – but this arrangement works so long as the UK is a part of the EU so there is freedom of trade and such. Out of the EU it may be a very different story.
It will have an effect, but I’m not sure catacylsmic. The main issue will be the banks and internationals who consider the UK as a gateway to the EU. It will be that Europe may be poorer if it loses this, but the effect of the UK is liable to be worse.
Why do you equate shafting the UK with destroying every country? That is more likely to happen in slow motion if the EU lets the UK retain access without the immigration.
No, it is part of the EFTA. And as such is part of the four freedoms.
I’m sure that by new other European countries have held discussions on how to proceed. It will not be easy, but the UK leaving won’t spell the end of the EU. It’s time to face the blunt obvious truth. Leaving the EU will not solve the problems that were frequently highlighted by the Leave campaigns – Nigel’s poster to the Boris Bus. Becoming an outsider to the Eurobloc will do that, but that is an idea bordering on the insane… |
Pages: 1 2