MiSTer FPGA Forum

Hello,

I have been very curious about this 18bit colour depth of the analog IO board's video output. Could maybe someone explain why it is just 18bit instead of 24bit? Was there any particular reason fur such design decision? And is it even possible/realistic that one day a new version of analog IO board would be released which could properly handle 24bit colour? Or is the direct video + DAC the only option to achieve that?

I understand that MiSTer was originally developed with 8/16bit consoles and computers in mind so 18bit colour could seem much more than actually needed back then, but now with the arrival of PSX core and N64 not being completly out of the cards, wider colour space seems essential and I am wondering if it is time already to look for a good DAC or wait for MiSTer development.

Many thanks in advance to anyone who answers.

Kind regards.

If I am not mistaken it uses a resistive DAC, the more colors the more I/O pins needed and also the resistors have to be very accurate.

jca wrote: ↑Fri May 19, 2023 8:54 pm

If I am not mistaken it uses a resistive DAC, the more colors the more I/O pins needed and also the resistors have to be very accurate.

Exactly this.

For those who, like me, want to have 24 bit colour analogue video output for their CRT's, and are struggling find a solution (again like me), it seems the only option currently available is a IOUSB PLUS/MINI board available from here:

• https://antoniovillena.es/store/product/iousb-plus/
• https://antoniovillena.es/store/product/iousb-mini/

It is R-2R DAC (full RGB range as confirmed with the creator via email) and uses additional pins of DE10 to produce 24 bit colour depth. At this moment, it is unclear to me whether it requires modified cores to make use of the additional pins and generate more colours. For sure it needs modified core for the handling enhanced SNAC port.

Obviously second memory module is not supported so you need to have that in mind hoping to play Saturn core in case it won't be eventually optimised for one module, or looking far more into the future and dreaming of Jaguar or 3DO.

Still, perfect for outstanding PSX core and likely for N64 coreif it will ever happen, as it seems it will be using DDR3 (though I may be completly wrong about this).

And I wrote "the only option" as there are no direct-video DACs in the existence that would be full RGB range and compatible with MiSTer. Those HDMI converters available everywhere are all the same and limited RGB range. I will be more than happy to hear that I am wrong on this so please correct me if you know of any full RGB one. It would be awesome if Analogue's DAC (https://www.analogue.co/dac) could be made compatible with MiSTer, but I am guessing Analogue is not interested in allowing ohters to integrate with their solution. So unless some magican on MiSTer scene could create similar solution dedicated to MiSTer, I suppose there will be no 24 bit video on CRT on cores supporting it but requiring two memory sticks. And that makes me sad :/

I am buying this IO board from Antonio.
Do I need modified cores for 24-bit colors?

I have a 24-bit analog board (mezzanine AV board)
All of the console cores I have tested work.

The only arcade core I have found that works (I have not tried anywhere near all of them) is the Cave core available on discord. It is dated 20240703

dickhardpill wrote: ↑Wed Jul 03, 2024 10:52 pm

I have a 24-bit analog board (mezzanine AV board)
All of the console cores I have tested work.

The only arcade core I have found that works (I have not tried anywhere near all of them) is the Cave core available on discord. It is dated 20240703

Do you mean arcade cores besides cave are not showing 24bit images or not working entirely?

They work via HDMI but nothing via analog out.