Hello there my fellow AmiBayers,
Wow this is most certainly a while since I started a new thread, so I thought this information should be re-usable for fellow forum chummies
So for the non technical, what is a Scan Doubler Flicker Fixer?
Well its best to tackle both of these independently -
Scan Doubling
This thread is about the Scan Magic (aka Flicker Magic) made by DCE, so without any more delay - let me introduce the
Scan Magic: Scan Doubler Flicker Fixer
As you can see the device is actually made up of two PCB boards, while the one on the right is what you might call the Business End, the one on the left is the Sync "pickup", thats the Vertical and Horizontal Sync collection.
This is needed to know, I suppose you could say the Shape of the image that is being generated.
Now, if you look closely to the daughter PCB on the left, in the bottom right corner of the 84way socket there is a small part filed away, this is so that it can fit flush to the motherboard, otherwise some SMD monolytic capacitors get in the way.
In the above picture some of you may notice some familiar hardware, namely the VP101 DAC (Digital to Analog Converter) it is actually of the same family that you will find on the A1200 and A4000 motherboard, although the revision is slightly different.
The real magic of the Scan Magic is done in the MACH chip, this small CPLD performs the collecting and writing of scan lines to the memory and screen output buffer (which is very small)
Heres an overview technical drawing of the Scan Magic
I have taken the opportunity to label holes 1 and 2 on both the daughter card and main PCB of the Scan Magic. Its a common fault for wire to snap from either end, and while wiring back up incorrectly wont damage the adapter its best to know where they go first time...
So lets look at installation -
This particular adapter is an Internal Adapter, as such it is only compatible with the A1200 and the A4000
A1200 Installation
Motherboard Orientation -
Scan Magic Installation -
A4000 Installation
Motherboard Orientation -
Scan Magic Installation -
Interestingly while this device would work on a CD32, there isn't enough physical room to actually install the device, well not without some serious hackery -
Colour Bits
I should mention (for completeness) that the Scan Magic is only an 18bit colour device - thats to say, it only has 6 bits of RED, 6 bits of Green and 6bits of Blue colour storage - where as AGA machines, like the A1200 and A4000 have infact 24 bit colour
So what does this all mean, well basically when you have a 24bit colour gradient - imagine a screen phaseing from blue to green - the picture on an 18bit output would not be as crisp, infact, you may notice some colour blocking.
However in terms of 95% of games and software, since it was written for ECS (16bit colour) you simply wont notice the difference.
So there you have it, a little story about a piece of nearly 14 year old history, thanks for reading.
Wow this is most certainly a while since I started a new thread, so I thought this information should be re-usable for fellow forum chummies
So for the non technical, what is a Scan Doubler Flicker Fixer?
Well its best to tackle both of these independently -
Scan Doubling
Simply put, this doubles the output vertical the scan rate from 15.1Khz to 31.2 KHz. It does this by copying the scan line, dublicating it and outputing it to a higher 31.2KHz refresh rate
The reason we do this is so we can display the output on devices that dont sync lower than 31.2KHz, while TV's (for the moment) will happily handle 15KHz vertical refresh signals, things like PC Monitors dont. So to use a PC VGA monitor, you need to have an output of 31KHz before the set can "pickit up"
It should be said that some PC monitors are Multi-Sync and will lock a picture at 15KHz (and lower), but it should also be noted that some (most) LCD monitors wont Sync down to less than 34KHz, as such a device like this would be incompatible.
Flicker FixingThe reason we do this is so we can display the output on devices that dont sync lower than 31.2KHz, while TV's (for the moment) will happily handle 15KHz vertical refresh signals, things like PC Monitors dont. So to use a PC VGA monitor, you need to have an output of 31KHz before the set can "pickit up"
It should be said that some PC monitors are Multi-Sync and will lock a picture at 15KHz (and lower), but it should also be noted that some (most) LCD monitors wont Sync down to less than 34KHz, as such a device like this would be incompatible.
Have you ever wondered why some screens flicker? have you ever wondered why would the programmer want to induce violent fit inducing visuals?
Unfortunately I cannot answer the latter, but the former is quite simple...
To get more information on the screen, the computer actually uses two screens of information, and then interpolates the pictures giving more detail...
sounds a bit funky, but bare with me, lets take the Amiga Hires of 640x256 - using this interpolation technique, you can now have 640x512 pixels - so a lot more information can be presented to the user. Unfortinately this interpolated, or I should say interlaced.
imagine clasping hands together... each hand is a screens worth of pixels (640x256) and your interlocked fingers are each a scan line of information
Back in the day this was a very cheap way of adding value to a product by giving more screen modes, however to be honest, unless you ejoy fit enducing headaches, then the interlaced flickering is truly abhorrent.
So now you know what produces the flickering, how does the Flicker Fixing work?
well it requires just a little memory to hold what is called a field I would like to call it about 4 and a half scan lines
So it de-interlaces these screens and re-intergrates the image as one picture of 640x512 pixels - think of it as taking a scan line from screen 1 onto output image, and then a scan line from screen 2 onto output image - this builds up a 640x512 image from two screens of 640x256.
See, it wasn't so scairy eh?
So now you know the basics, you can now see what a Scan Doubler & Flicker Fixer actually does to the output signals of your Amiga.Unfortunately I cannot answer the latter, but the former is quite simple...
To get more information on the screen, the computer actually uses two screens of information, and then interpolates the pictures giving more detail...
sounds a bit funky, but bare with me, lets take the Amiga Hires of 640x256 - using this interpolation technique, you can now have 640x512 pixels - so a lot more information can be presented to the user. Unfortinately this interpolated, or I should say interlaced.
imagine clasping hands together... each hand is a screens worth of pixels (640x256) and your interlocked fingers are each a scan line of information
Back in the day this was a very cheap way of adding value to a product by giving more screen modes, however to be honest, unless you ejoy fit enducing headaches, then the interlaced flickering is truly abhorrent.
So now you know what produces the flickering, how does the Flicker Fixing work?
well it requires just a little memory to hold what is called a field I would like to call it about 4 and a half scan lines
So it de-interlaces these screens and re-intergrates the image as one picture of 640x512 pixels - think of it as taking a scan line from screen 1 onto output image, and then a scan line from screen 2 onto output image - this builds up a 640x512 image from two screens of 640x256.
See, it wasn't so scairy eh?
This thread is about the Scan Magic (aka Flicker Magic) made by DCE, so without any more delay - let me introduce the
Scan Magic: Scan Doubler Flicker Fixer
As you can see the device is actually made up of two PCB boards, while the one on the right is what you might call the Business End, the one on the left is the Sync "pickup", thats the Vertical and Horizontal Sync collection.
This is needed to know, I suppose you could say the Shape of the image that is being generated.
Now, if you look closely to the daughter PCB on the left, in the bottom right corner of the 84way socket there is a small part filed away, this is so that it can fit flush to the motherboard, otherwise some SMD monolytic capacitors get in the way.
In the above picture some of you may notice some familiar hardware, namely the VP101 DAC (Digital to Analog Converter) it is actually of the same family that you will find on the A1200 and A4000 motherboard, although the revision is slightly different.
The real magic of the Scan Magic is done in the MACH chip, this small CPLD performs the collecting and writing of scan lines to the memory and screen output buffer (which is very small)
I have taken the opportunity to label holes 1 and 2 on both the daughter card and main PCB of the Scan Magic. Its a common fault for wire to snap from either end, and while wiring back up incorrectly wont damage the adapter its best to know where they go first time...
This particular adapter is an Internal Adapter, as such it is only compatible with the A1200 and the A4000
A1200 Installation
Motherboard Orientation -
Scan Magic Installation -
Motherboard Orientation -
Scan Magic Installation -
Colour Bits
I should mention (for completeness) that the Scan Magic is only an 18bit colour device - thats to say, it only has 6 bits of RED, 6 bits of Green and 6bits of Blue colour storage - where as AGA machines, like the A1200 and A4000 have infact 24 bit colour
So what does this all mean, well basically when you have a 24bit colour gradient - imagine a screen phaseing from blue to green - the picture on an 18bit output would not be as crisp, infact, you may notice some colour blocking.
However in terms of 95% of games and software, since it was written for ECS (16bit colour) you simply wont notice the difference.
So there you have it, a little story about a piece of nearly 14 year old history, thanks for reading.