XPost: comp.sys.ibm.pc.classic   
   From: nospam@invalid   
      
   In news:yNudnYt8VcpQ753WnZ2dnUVZ_gOdnZ2d@westnet.com.au Mark McDougall   
   wrote:   
      
   > Horst Franke wrote:   
   >>>> NO, by _technical_ reasons there's no way to perform this!   
   >> Sorry Mark, but explain your "wrong statements" more precisely!   
   >   
   > You state emphatically that it is technically _impossible_ to convert   
   > CGA to VGA. That statement is simply incorrect. I don't really   
   > understand what you are asking me to explain?   
      
   >> Why do you want to design a converter while native design is   
   >> appropriate?   
   > I don't understand this statement.   
      
   Ok. Then see my example with the chinese translator.   
      
   >> And you state *won't be cheap*?   
   >> Any converter will loose something of the original!   
   >> OK, you want to make money - but there's no technical reason behind.   
   >> See also the later issues that provide more details about possible   
   >> problems.   
      
   > The video converter was never driven by any particular desire to   
   > convert CGA to VGA - in fact I didn't even have CGA in mind when   
   > specifying the TTL interface - and we started on it well before this   
   > thread arose. I mentioned the converter here only because it will   
   > happen to support CGA-VGA.   
      
   > Make money? No, defintitely not. This converter was borne out of a   
   > need by myself and my colleague to support a large variety of retro   
   > computers on VGA monitors. My 4th 1084S recently died, and it's   
   > impractical to keep repairing them. They also take up a lot of room.   
   > So we decided to design a single box that we could use on the various   
   > TRS-80's, Apples, Commodores, Sinclairs, Sord M23 etc, not to mention   
   > the retro consoles we have as well. If we sell a few to help fund the   
   > development costs, then great!   
      
   OK, but I think there's no relation to IBM PC CLASSIC.   
      
   > A for _losing_ detail (note spelling) - that's not necessarily the   
   > case. You keep mentioning "loss of detail", but neglect to supply any   
   > technical explanation of what you're referring to. So I will.   
      
   > One issue is sampling of the CGA signal in sync with (and centred on)   
   > the dot clock from the CGA card. Unfortunately CGA, unlike some other   
   > TTL video outputs, does not supply the dot-clock on the interface. So   
   > in the case of CGA it is more problematic. It is possible to do   
   > clock-recovery given a suitable output, or it is possible to   
   > super-sample the output and work back from there. I am yet to decide   
   > what method(s) we will employ - but most likely will simply lock a   
   > clock to each hsync, which is how most video sampling ICs work.   
      
   Sorry but that technical detail was out of my mind.   
   I responded from an end user point of view.   
      
   > A 2nd issue will be up-scaling the display to the native resolution   
   > of the monitor. Obviously not an issue when the native resolution is   
   > an integer multiple of the CGA output, but this won't always be the   
   > case. But we will be using sophisticated scaling algorithms that do a   
   > good job of scaling.   
      
   NO. This is convertion issue but not native related.   
      
   > So the problem won't be _loss_ of detail, but rather loss of   
   > definition, if you like. However, given the relatively low resolution   
   > of CGA, scaling algorithms and relatively high resolution of modern   
   > VGA monitors, I very much doubt that anyone could complain about the   
   > quality. This is not about reproducing an absolutely _perfect_ CGA   
   > output (_any_ conversion by its very nature is going to fall short   
   > here), it's about producing the best possible output on a VGA monitor.   
      
   ACK from my site. But I don't like "definition" in this context.   
   And CGA low resolution should everyone understand.   
      
   > To be clear, I'm not proposing at all that our box is cost-effective   
   > for anyone who wants to _only_ do CGA-VGA - far from it! But if you   
   > own a range of *PAL* and NTSC computers/consoles that have composite,   
   > s-video, component, analogue rgb and digital rgb outputs (as I do)   
   > and want to be able to display them _all_ on a single VGA/DVI monitor   
   > - scaled to fit the whole screen, or scaled approriately on a   
   > wide-screen monitor - then you may wish to consider our box.   
      
   OK. ACK.   
      
   >> My issue is that native presentation by an adapter (VGA card) will be   
   >> more cost sensitive than any converter.   
      
   And why you then state it's not cheap?   
   A VGA adapter should be less than 20 USD.   
      
   >> I don't see any reason why to use such old boards any more.   
   >   
   > That's not the point at all. Wesley _wants_ to use an old computer   
   > for his own reasons - you can't just say "I don't see any reason to   
   > use such an old board, get a newer one".   
      
   Ok, but then he will need to look for "personal" solution.   
   Either he already have a CGA monitor or need to "upgrade".   
      
   Routed to comp.sys.pc.classic   
   Horst   
      
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