Ebay CGA to VGA adaptor

[alexh]

This is the Cypress CM397

http://www.cypuk.com/cyp_techpage.php?product=259&&parent=

Although they say CGA to VGA adapter, they are actually Analog RGB to VGA adapters. CGA is not an analog video format it is a 4-bit digital (TTL) signal.

They are in theory 16-bit scandoublers, but in practice (because they resample the analog signals) they are much worse than that, closer to 12-bit, and so are ok for OCS/ECS but not really suitable for AGA screens (unless you want to loose colour information).

$90 is a good price, but it is not the cheapest scandoubler available.

Like all of scandoublers on the market they are quite expensive for what is actually inside them.

[alexh]

machinehead wrote:
Even AGA is 16 bit "at best" due to the "custom chip set" and all that, more like 12 bits.

No it isnt. It's 24-bits. The old Amiga Chipset (OCS/ECS) is 12-bits.

And what exactly is inside a scan doubler? I opened a "Toast Scan" and was rather impressed by the complexity of the circuit.

The ToastScan is a VERY VERY old design, it is overly complex and uses lots of discrete components:

o ADC (Analog to digital converter) which samples the RGB out of the Amiga back into a digital signal
o CPLD (Programmable Logic Device) the core logic of the scandoubler, programmed to see the 15KHz horizontal & vertical sync signals and copy the RGB digital data into RAMS and read them back out at the appropriate timing for 31KHz.
o RAM (Usually 2x Frames of data for the Flicker Fixer, 2x Lines for the Scandoubler, sometimes expensive 2-port RAM)
o DAC (Digital to Analog converter) to convert the scandoubled 31KHz digital RGB signals back into Analog.

Today all of these parts (RAM, DAC, CPLD) are all inside one very cheap chip.

machinehead wrote:
Don't forget the "Toast Scan" is $160.00 when and if it is re-released. Software Hut says there is a critical part unavaliable that is causing the delay.

There will be no more ToastScan (Indivision) devices. The people who make them (Jens Schoenfeld) has used all his MACH (CPLD) parts, it is difficult/impossible to get more.

machinehead wrote:
So actually, a scan doubler is quite complex and because of the small market, are somewhat expensive.

Not completely true. Ok, a fully made up Amiga specifc scandoubler has a small market, but scandoublers in general have a huge market.

There is a scandoubler in every LCD-TV, millions sold everyday and that makes the chips that go inside them cost almost nothing. Less than $3 each.

machinehead wrote:
So if they are all the same and there are cheaper ones, can you point us to them?

I didnt say they were all the same.

A guy called Roy R. Justus was selling external 16-bit Flicker Fixing scandoublers (equivalent to the Cypress one) for $48 each, but that was before the US dollar crash.

http://www.miba51.com/CoCo_VGA_Adpater.html

machinehead wrote:
Being this is the only one (I could find) that actually exists I thought $90.00 wasn't too bad.

It's not the only one, just google and you'll find at least 10 and I said $90 was a good price.

[alexh]

machinehead wrote:
But name 5 applications that make use of AGA

1017 : http://aminet.net/demo/aga I love AGA demo's, dont you?

10 decent games?

Aladdin
Alien Breed 3D (/II)
Chaos Engine II
Liberation: Captive II
Brian the Lion
Second Samurai
Speris Legacy
Super Stardust
Street Racer
T-Zero
The Misadventures of Flink

I am sure there are more, but these were all I could think of in 5 mins. But I agree with you, there are not that many compared with ECS games.

I didn't ask how old the Toast Scan was, I just said it is complex and I stand by that remark.

You are right, it is too complex for the ordinary user to replicate.

And VERY VERY old? You mean like an Amiga 1200?

I believe that technology used in the ToastScan pre-dates the A1200. It is not an original design, it was bought from another company, where it was sold under a different name (EZ-VGA, Indivision, ToastScan etc. all the same thing)

How would I interface this "$3.00" chip to the RBG output of an Amiga 2000?

You'd have to make a PCB.

The wiring is ultra simple, 6 wires from the Amiga video port (Red, Green, Blue, HSync, VSync, +12v, Gnd). RGB analog are wired to the AL875 and 15-bits digital output from AL875 are wired to AL250A along with HSync, VSync. You'd need some power regulators to convert the +12v into the supply required, also some pull up resistors.

It's probably beyond the home user, perhaps 2hrs of research and 5hrs of CAD to create the PCB but you'd get a reference design from the vendor for ideas.

This is exactly what Roy Justus did, he developed his own, he one that sold for $48.

How come no one is ripping these out and selling them on Ebay?

I think "ripping them out" wouldnt be cost effective ;-)

BUT you can buy them direct from the manufacturer in low numbers. What do you think is inside the CM397 you bought? Yup, probably the same chips that are in a lot of LCD-TV's, the Averlogic AL875 + AL250A chips.

If I could make this work on an Amiga, you can Bet Your Ass that it would cost you more than $3.00.

At a guess, I would expect you could make them for a cost of about $500 for the first and $15 for each after. You'd have a MOQ (Minimum order quantity) of about 200. But they would still not give correct colour representation in AGA modes.

Isn't that the reason the market is flooded with scan doublers for the Amiga? :shrug:

The market isnt flooded because there isnt one. At least not a big enough one to warrant the time and energy required to research, design and manufacture (and deal with all the associated headaches). You might sell 200, make a profit of $30 on each. A huge profit of $6k not worth the effort.

Please contact Software Hut and tell them to take down the Pre-Order Toast Scan page.

Soft-Hut never update their webpage, they never do. Even after they were found selling pirate software in 2000.

http://www.softhut.com/cgi-bin/test/Web_store/web_store.cgi?page=catalog/software/entertainment/ambermoon.html&cart_id=4870038_84978

I've spoken to Jens Schoenfeld since this was posted on Soft-Hut and he said that he wasnt working on a replacement Toastscan but was concentrating all his efforts on Clone-A. That's not to say he hasnt changed his mind.

And despite your negitivity, I will post the results so that others may benefit if they so choose.

No negativity intended, just plain facts. This subject, and this exact scandoubler has been discussed before on this forum. If you get the Cypress CM397 CGA to VGA adapter you will not get correct representation of colours in AGA modes, simple as that.