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General Category => Amstrad CPC hardware => Topic started by: awergh on 15:26, 13 April 10

Title: Best way to experience the world in Colour
Post by: awergh on 15:26, 13 April 10
So I have two 464s and two GT64s but I'm sure it would be good to be able to see colour.
I actually had a strange dream about going absailing off some cliff into a valley to rescue a CTM640 for some reason I didnt actually get to that part of the dream I was just about to.
I did see a CTM644 for sale on some website but with shipping to Australia it came out to be a bit too expensive.
Is RGB to SCART and then SCART to VGA not possible?
I don't have a TV with SCART anyway so I'm not sure SCART is an option, maybe I should just try build myself a parallel cable because that would be more possible.
Still it would be nice to be able to play some games in Colour afterall Colour should always be better.
Title: Re: Best way to experience the world in Colour
Post by: MacDeath on 16:56, 13 April 10
It may depends of the budget/amount of money you may spend in this.

A modern flat screen is a problem as nowaday most (=all) screens come in 16/9.

It was sort of disapointment to me in retroMadrid as many machines (computers or even Arcade games) were displayed on 16/9 monitor with no re-dimension...

Metal slug in large is bad bad bad...
also c64 in large pixel mode and large screen is awfull...

And just imagine an atari 2600 (large larger pixels...ouch...)

The best way may be to find a TV with sweet re-dimension options, or better : a 4/3 flat screen.

Recently I was installing some machines in a factory and they had 4/3 flat VGA screens...But a VGA adapter is perhaps not as easy to craft as a Scart/perital adaptator ?

Also Most VGA screens don't feature re-dimension options.


But from what I saw, a CPC on a TV is not that good too.

I put some of mine on my big old school TV (Peritel) and pixels were not quite precise...
Blured indeed.

it's definitely a problem and i believe if a manufacturer could release a proper 4/3 flat monitor designed and advertised as a Retro computering/gaming specific model, with perhaps sweet in built plugs and/or a range of adaptators for the common machines and so on...

such a monitor would indeed sell well in the retrocomputer/console world.
Title: Re: Best way to experience the world in Colour
Post by: awergh on 03:38, 14 April 10
I have plenty of 15" CRTs that I could use with VGA adapter, but I gather that is a bit harder.
This is something I am willing to try though.


A retro monitor indeed would be cool, if only we had friends in those places.
Title: Re: Best way to experience the world in Colour
Post by: arnoldemu on 11:38, 14 April 10
I have plenty of 15" CRTs that I could use with VGA adapter, but I gather that is a bit harder.
This is something I am willing to try though.


A retro monitor indeed would be cool, if only we had friends in those places.
The problem with most VGA CRT monitors is the horizontal rate is 31Khz. For CPC you need 15Khz.
SCART is much better!
Title: Re: Best way to experience the world in Colour
Post by: awergh on 12:10, 14 April 10
Hmm... but the TV only has composite video whats RGB to SCART to composite like?
Title: Re: Best way to experience the world in Colour
Post by: robcfg on 13:03, 14 April 10
Actually, the SCART (http://en.wikipedia.org/wiki/SCART) connector can carry RGB, S-Video and Composite signals at the same time (It can have any of these or all together).


Ideally if you could find a VGA Box that allows RGB input, it would be the best option, but most of them only allow composite input which leaves us at the beginning of the problem again because you still need to convert the RGB signal to composite.


Regarding quality, RGB is always the best quality.
Title: Re: Best way to experience the world in Colour
Post by: nocash on 14:34, 14 April 10
Hi. Could think of two solutions...

For TV. Since your TV has no RGB input, you'd need a RGB-to-composite converter. Like the http://cpcwiki.eu/index.php/Amstrad_MP1/MP2_modulator (you're using PAL in australia, too, don't you? And shipping may be cheaper than monitors). The problem with the MP1/MP2 is they do output only normal TV signal with poor quality. The raw composite signal is present internally, with some small modification you could wire that to the V input your TV (not having SCART, you DO have an A/V input with cinch connectors, don't you?).

---

For VGA. I've been wondering about that for a while, too. The VGAs higher horizontal clock (=higher vertical resolution) would be the main problem. TV (and CPC) has circa 250 lines, classic VGA has circa 480 lines. Newer SVGA also supports 600 lines, 768 lines, 1024 lines, etc. That is: higher resolutions. But if the monitor hardware is made flexible, it may also be able to handle lower resolutions.

The VGA input doesn't really need to support lower resolutions, but it may be there as hidden feature. I think, old CRTs (until 1993 or so) contained separate clock generators for each resolution, so chances are bad that they have one for CPC resolution. Newer LCDs (and maybe also newer multisync CRTs) may have better chances. Especially if they do also include a TV input, or if the manufacturer used the same components also in TVs - then they have kept the low resolution support also on the VGA input.

So far in theory. Looking here, http://forums.bit-tech.net/showthread.php?t=152858 it seems that SCART to VGA is possible, and at least one of them got it working, though with a greenish picture (which may be easy to fix). SCART is more or less the same as CPC monitor, so CPC to VGA should work the same way.

Dunno if the RGB-VGA voltages are safe. SCART RGB is 0.7V peak-to-peak. On my CPC I measured around 0.3V=black, 1.0V=bright, which would be 0.7V peak-to-peak with a 0.3V offset. That, with the CPC connected to a TV with RGB input. When not connected (=no load on the monitor output), it gives 4.0V=bright, which would be pretty high (the VGA might apply a similar load, so the signal might drop to suitable 1.0V or less, too).

Guess, I will give it a try... Wiring RGB-to-VGA looks simple. And would be interesting to see if it blows up the video input of my PC screen :-)
Title: Re: Best way to experience the world in Colour
Post by: robcfg on 16:50, 14 April 10
The problem there is not that you can't physically connect the RGB output to the VGA input, but the refresh rate.


The most probable outcome for your experiment is your monitor telling you that the input signal is out of range.


Maybe it would work if you have a multisync monitor... maybe...
Title: Re: Best way to experience the world in Colour
Post by: awergh on 03:47, 16 April 10
Yeah I have cinch connectors (not that I'd heard of them called that before, wikipedia knows everything though), IT would have to be PAL yes. MP1/MP2 would be cheaper to ship much lighter.
I do have some other CRTs but I have no idea if they would work, I like the idea of RGB to VGA because it doesn't require modification
Title: Re: Best way to experience the world in Colour
Post by: archcosmo on 14:10, 16 April 10
Hi there,

There's a few options out there, depending on what connections your monitor/TV screen has available

for VGA monitor, you'll need an upscan converter: RGB from the CPC is using 15kHz horizontal refresh, whereas VGA (SVGA, XVGA etc) uses 30kHz horizontal refresh, so not compatible without some kind of scandoubling..

the best example of these gadgets would be Micomsoft XRGB2 - see here
 (http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=270561297292)
or this (http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=260383584808&ssPageName=STRK:MEWAX:IT) kind for use on plasma TV

or perhaps something like this (http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=370365401504) - requires you to make a suitable input cable though, as it's meant for JAMMA arcade cabinet use

for a modern TV/combo LCD with component YPbPr input, you could use one of these (http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=140322681196) CSY2100 SCART RGB to Component converters (just need a separate cable for audio)

my personal preference is to get a Commo'dore (*) 1084 (or 1084S with 9pin Dsub port) CRT monitor, and wire up a suitable cable.... or find a combo LCD TV/DVD unit with VGA/SCART input for the same result....

good luck!

(*) apostrophe added to defeat the weirdness with the text preview - it was showing up as COMMODORK ?!
Title: Re: Best way to experience the world in Colour
Post by: nocash on 15:53, 16 April 10
I've gave it a try and built a CPC to VGA adapter (just some wires, no extra electronics), and tested it with two VGAs.

First, on a Fujitsu TFT from 2008 or so: Didn't work, displayed "Out of Frequency". A pity, being an TFT, it's digitizing the RGB input, buffering it in RAM, and upsampling it to 1024 lines. So, hardware-wise, there's absolutely no reason why it shouldn't work. As it seems, the software-devrs have chosen to include a IF LINES<400 THEN PRINT "OUT OF FREQUENCY" feature :-( Still it might have good chances with TFTs from other manufacturers.

Second, on a ARX CRT from 1992 or so: Gives a picture, but breaks each CPC scanline into two VGA scanlines: First VGA line is left half of first CPC line, second VGA line right half of first CPC line, and so on. Not too surprising since it's an old raw analogue CRT with separate potentimeters inside for manipulating each of the support 3-4 video resolutions. And as far as I know, most or all CRTs are directly forwarding the incoming signal to the electron beam (without using the resampling method found in TFTs).

If you have a lot of VGAs, it may be worth building the adapter, and trying it with all VGAs. Though, since you said you have old CRTs, chances aren't too good, TFTs should be more likely to work.
PS. I needed to connect VSYNC and HSYNC (CRTC chip pin40 and pin39), the both-in-one SYNC (on CPC monitor output) didn't do it.
Title: Re: Best way to experience the world in Colour
Post by: orange on 19:22, 16 April 10
you need scandoubler. its a well known problem in Amiga world. and other such computers.
unfortunately it costs from 70 to 100 euros.

or you can use multisync VGA monitor. they used to make some CRTs like that. dunno about these newer ones.

still, best solution is to get LCD or plasma TV with RGB SCART.
Title: Re: Best way to experience the world in Colour
Post by: OCT on 20:23, 16 April 10
Wouldn't the first thing one needs in nocash's experiment often be a sync separator, as VGA expects the horizontal and vertical pulses on different pins (13&14), while the CPCs and SCART use a composite sync signal, which isn't supported by all monitors on pin 13 ?
Title: Re: Best way to experience the world in Colour
Post by: Alcofribas on 20:30, 16 April 10
There is an interesting topic about BenQ G2420 & 15khz resolutions with A1200 (http://eab.abime.net/showthread.php?p=609751).
Title: Re: Best way to experience the world in Colour
Post by: nocash on 21:42, 16 April 10
> Wouldn't the first thing one needs in nocash's experiment
> often be a sync separator
Not fot the CPC... I've had wired it to HSYNC and VSYNC, not to SYNC (see postscriptium in above message).

> composite sync signal, which isn't supported by all monitors on pin 13 ?
Ah, that would be an optional feature, supported by some monitors?
Been wondering why the VGA pinouts listed that pin as "hsync or composite sync". On my old CRT-VGA that input took only hsync. But if newer VGAs accept comp.sync, then one wouldn't even need to attach wires to the CRTC chip.
Title: Re: Best way to experience the world in Colour
Post by: OCT on 21:44, 16 April 10
There is an interesting topic about BenQ G2420 & 15khz resolutions with A1200 (http://eab.abime.net/showthread.php?p=609751).
Regrettably for a line of monitors that gets quite some heavy spanking in consumers' forums: http://geizhals.at/eu/?sr=475490,-1,0 (not sure what differences precisely the trailing letters indicate)
Title: Re: Best way to experience the world in Colour
Post by: awergh on 06:18, 17 April 10
Well the Micomsoft XRGB2 is definitely not an option on that link since I might as well buy a CTM644 then.
The problem with an RGB to VGA board is that I think I didn't want to spend too much.
The CRTs are manufactured in 94,94,96,99 the 17" 2001 and this 19" I didn't look cause then I might have to clean the dust.
Here is the info on the 99 one I found http://www.mitsubishielectric.com.au/2331.htm if that tells you anything at all.
There are 2 19" LCDs but they aren't mine so I'm not counting them 
Title: Re: Best way to experience the world in Colour
Post by: nocash on 00:39, 23 April 10
Hi awergh, you (and your cpcs) are from australia, aren't you? Just read that australian cpcs would display "Awa 64K Microcomputer" instead of "Amstrad 64K Microcomputer" in the boot message - is that true?

Found that info here, http://amstrad.cpc.free.fr/article.php?sid=13 don't know how serious that page is (it also has the cpc5512, http://amstrad.cpc.free.fr/article.php?sid=14 though that one is marked as fake).
Title: Re: Best way to experience the world in Colour
Post by: awergh on 09:32, 23 April 10
It looks like it is true I assumed it wasn't but I just checked both my CPC464s and they show Awa 64K Microcomputer
I've never noticed that before the message underneath is the same though, I would of told you it wasn't true without looking if I'd posted earlier this morning.
Title: Re: Best way to experience the world in Colour
Post by: Gryzor on 12:25, 23 April 10
Awa, eh? Imagine that! Anyone has any details on Awa?

Can you post a photo? :)
Title: Re: Best way to experience the world in Colour
Post by: Axelay on 13:48, 23 April 10
It looks like it is true I assumed it wasn't but I just checked both my CPC464s and they show Awa 64K Microcomputer
I've never noticed that before the message underneath is the same though, I would of told you it wasn't true without looking if I'd posted earlier this morning.

You really had to check?!  I reckon you might have been using emulators too much!  :P

The thing I've always wondered about is why the 464 says Awa, but the 6128 I got a couple of years later says Amstrad.
Title: Re: Best way to experience the world in Colour
Post by: Devilmarkus on 14:37, 23 April 10
Special top-secret info for Gryzor:
Let's have a deep look into the CPC rom:
Code: [Select]
00000730h: 7E 23 B7 20 FB 10 F9 C9 41 72 6E 6F 6C 64 00 41 ; ~#· û.ùÉArnold.A
00000740h: 6D 73 74 72 61 64 00 4F 72 69 6F 6E 00 53 63 68 ; mstrad.Orion.Sch
00000750h: 6E 65 69 64 65 72 00 41 77 61 00 53 6F 6C 61 76 ; neider.Awa.Solav
00000760h: 6F 78 00 53 61 69 73 68 6F 00 54 72 69 75 6D 70 ; ox.Saisho.Triump
00000770h: 68 00 49 73 70 00 FE 03 D0 F3 D9 CB 89 CB 81 B1 ; h.Isp.þ.ÐóÙˉˁ±

All these names were possible in startup-screen.
Changeable by jumpering/opening some LK-bridges on the CPC board. (The last LK-bridge in this row is to toggle between 60/50 hz)

Edit: For some reason the name "Arnold" was not chooseable!
Title: Re: Best way to experience the world in Colour
Post by: Gryzor on 15:05, 23 April 10
<sarcasm>Ooooh thanks! By gods, I had never heard of that before! </sarcasm>

I was just saying I haven't actually seen it on-screen...
Title: Re: Best way to experience the world in Colour
Post by: Devilmarkus on 15:17, 23 April 10
<sarcasm>Ooooh thanks! By gods, I had never heard of that before! </sarcasm>

I was just saying I haven't actually seen it on-screen...

<sarcasm>No eyes, no see</sarcasm>

We played with these LK bridges already in the 80s. I also had a 60hz switch in my 464 ;)
Title: Re: Best way to experience the world in Colour
Post by: Gryzor on 16:06, 23 April 10
Never had one (60Hz switch, that is). Does it make a lot of difference?
Title: Re: Best way to experience the world in Colour
Post by: Devilmarkus on 16:07, 23 April 10
Never had one (60Hz switch, that is). Does it make a lot of difference?

It's not really necessary, that you would have a 60hz switch. It's absolutely enough when your CPC has one.
Well some things are faster then, with 60hz, also the sound.
Title: Re: Best way to experience the world in Colour
Post by: awergh on 17:05, 23 April 10
Yeah well I wanted to check, I don't use emulators that often, I probably wouldn't use them if I had a better way of getting games onto my CPC then going out and buying some blank tapes to record to.
I probably didn't notice it because it says Amstrad everywhere else.
I'll see if I can get a photo later bit late now
Title: Re: Best way to experience the world in Colour
Post by: ukmarkh on 18:48, 23 April 10
The games run at exactly the same speed... regardless of the amstrad Hz
Title: Re: Best way to experience the world in Colour
Post by: Devilmarkus on 19:16, 23 April 10
The games run at exactly the same speed... regardless of the amstrad Hz

Thats not quite correct.
Games or demos which use VSync as timing would be faster.
Title: Re: Best way to experience the world in Colour
Post by: arnoldemu on 19:21, 23 April 10
The games run at exactly the same speed... regardless of the amstrad Hz
If games set the crtc registers they will not work with 60Hz, because they will reset the screen refresh back to 50Hz.

Essentially yes the game code takes the same time *but* if the game is   syncing with the vsync then there could be less wasted time.
  potentially games could run smoother or slightly faster at 60Hz, but it depends.
It depends on if there is wasted frame time.
e.g.
a game which runs at 25Hz (because it is slower than 50Hz, but has some wasted time until the next vsync and waits for a vsync for displaying graphics).
Could run at 30Hz (if the time the game takes is <2 frames at 60hz).
So effectively the game is running faster and smoother.
Really depends on what time the game is using.