vga, xvga, svga

azagaros70 · Post by **azagaros70** » Mon Feb 22, 2021 12:49 am

As far as I know, the vera should be able to do any mode that was on the vga connector. Why did you stop at vga? the fpga should be able to handle the color concepts and the higher pixel maps. vga is 16 bit and svga 24 and the other 32. why did you use a 6502 instead of a 65c02-14?

Elektron72 · Post by **Elektron72** » Mon Feb 22, 2021 1:07 am

15 minutes ago, azagaros70 said:

why did you use a 6502 instead of a 65c02-14?

The Commander X16 is using a 65C02S, according to the FAQ. As for the VERA, more advanced video would likely consume too much VRAM to be practical, as the VERA is limited to 128K of memory.

azagaros70 · Post by **azagaros70** » Mon Feb 22, 2021 1:54 am

It is the same chip.. I did not realize that.. Ram is cheep.. It is just the addressing scheme on the fpga.. Memory is cheap. you can map the video memory

x16tial · Post by **x16tial** » Mon Feb 22, 2021 2:12 am

I'd recommend watching David's (8-bit Guy) videos on his "Dream Computer", there are 2 parts. He goes into many of the details and design decisions.

They are close to the top of the FAQ page.

StephenHorn · Post by **StephenHorn** » Mon Feb 22, 2021 2:51 am

No, the VERA cannot just do any signal that was ever put on a VGA cable. No, it is not just a matter of memory.

Want to change the resolution? That means changing the pixel clock speed. It also means implementing additional smarts in the video processing to deal with rasterizing lines of multiple widths (and not at a convenient power of 2, either). This likely means having to put the VERA onto a more expensive FPGA to support the additional sophistication.

Even if it were just a matter of memory, the VERA's memory is built in with the same FPGA used to implement the video processing. This kind of memory is not cheap. The cheap kind of memory would mean redesigning the entire daughter board for the FPGA chip to use external memory, and this still represents increasing the cost of the VERA due to the added components needed to deal with the external memory source.

Cyber · Post by **Cyber** » Mon Feb 22, 2021 4:34 am

3 hours ago, azagaros70 said:

As far as I know, the vera should be able to do any mode that was on the vga connector. Why did you stop at vga? the fpga should be able to handle the color concepts and the higher pixel maps. vga is 16 bit and svga 24 and the other 32. why did you use a 6502 instead of a 65c02-14?

The main goal is to recreate an 8 bit computer in the modern world, using available off the shelf components. It is ok for this computer to be a little bit more powerful than computers of 8 bit era, but it should not be too powerful, so to keep the 8 bit spirit. Another goal is to use a simple architecture, so one person coluld understand what each component do and how they interact.

More details here: http://www.the8bitguy.com/2576/what-is-my-dream-computer/

And here: https://www.commanderx16.com/forum/index.php?/about-faq/

BruceMcF · Post by **BruceMcF** » Mon Feb 22, 2021 7:45 am

5 hours ago, azagaros70 said:

It is the same chip.. I did not realize that.. Ram is cheep.. It is just the addressing scheme on the fpga.. Memory is cheap. you can map the video memory

Is RAM built into an FPGA actually all that cheap? Did you price the families of FPGA with built in SRAM before making the claim?

It's pretty central to the row buffer design that the SRAM the VERA is accessing is dual port asynchronous memory that VERA can access while running at 50MHz internally. Otherwise you lose a lot of your sprite per row capability.

kelli217 · Post by **kelli217** » Mon Feb 22, 2021 8:25 am

The highest resolution I ever personally have seen sent down a VGA cable is 2048×1536. I think it is unreasonable to expect VERA to be able to do this, even in monochrome, much less 24-bit color (or 32-bit including an 8-bit alpha channel) and still meet the price point the team is targeting.

Cyber · Post by **Cyber** » Mon Feb 22, 2021 8:57 am

32 minutes ago, kelli217 said:

The highest resolution I ever personally have seen sent down a VGA cable is 2048×1536. I think it is unreasonable to expect VERA to be able to do this, even in monochrome, much less 24-bit color (or 32-bit including an 8-bit alpha channel) and still meet the price point the team is targeting.

I think you are missing the point and project goal.

BruceMcF · Post by **BruceMcF** » Mon Feb 22, 2021 10:09 am

19 hours ago, kelli217 said:

The highest resolution I ever personally have seen sent down a VGA cable is 2048×1536. I think it is unreasonable to expect VERA to be able to do this, even in monochrome, much less 24-bit color (or 32-bit including an 8-bit alpha channel) and still meet the price point the team is targeting.

And the price point is just one part of it. It's an 8bit system with an 8bit processor driving an 8bit data bus. What would be the point of 24bit color support,for 1280x1024? How effectively could the 65c02 support it?

640x480 has a very real point: it allows 80 column text mode. Once that is hit (as some if not all 8bit systems did), the question becomes WHY raise the cost of the system with the next tier up FPGA in both number of available slices and available built in SRAM?

There's always "more" to be hit in terms of resolution, which is why they are now pushing consumers to "upgrade" to 4K TVs. To paraphrase Jurassic Park, "your computer scientists were so busy trying to find out how to do it, they forgot to ask WHETHER they should do it."