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vga, xvga, svga


azagaros70
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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?

Edited by azagaros70
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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.

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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.

Edited by x16tial
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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.

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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/

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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.

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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.

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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.

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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."

Edited by BruceMcF
It was possible to misread the original phrasing in an angry tone of voice.
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20 minutes ago, BruceMcF said:

It's about more than price point. 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."

Right.

I was merely adding yet anooooother reason why not.

It wasn't intended to be 'the only valid reason.'

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Also isn't it more fun to work with the constraints we have now!

Instead of having a 16 or even 32 bit true color screenmode we could try to do something like FLI on the C64 where a bitmap image was showing MORE colors by changing the palette every X scanlines or interpolating 2 colors in interlaced frames....   This kind of trickery is for me a big part of the charm of the original 8 bit systems. Push them to the limits and beyond normal expected results by using interesting new tricks.   I wonder what we can do with the Vera 🧙‍♂️ 

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5 hours ago, Robinkle said:

640x360 would be pixel perfect with HD, 1440p and 4K displays. I would like to know if this was considered. It makes sense mathematically at least.

The design target was to run on original VGA, and original VGA was a 4:3 ratio display, not a 16:9 ratio display. Indeed, that was a secondary strike against the original FPGA video chip design, though the primary strikes were device contention between 6502 bus access and the J1 coprocessor and the lack of a true bitmap mode.

Indeed, you can easily do a 640x360 display by just setting black bars at the top and bottom, and if shown on a TV with all the display options, it would fit. And 640x480 is pixel perfect on a 1440p display if you adjust the display width correctly.

Edited by BruceMcF
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11 hours ago, Robinkle said:

640x360 would be pixel perfect with HD, 1440p and 4K displays. I would like to know if this was considered. It makes sense mathematically at least.

There is no such mode in the VGA specification. So no, I doubt they considered a resolution that does not exist. 

 

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On 2/22/2021 at 4:13 PM, codewar65 said:

640x480 is about all the VRAM on VERA can handle; and about what a 65x02 @ 8MHz can handle populating the VRAM in a timely manner.

This Resolution and the Palette that the VERA is offering is more than enough for an 8-Bit Computer and it's more powerful than a TG16/PCE.

I'm not from the C64 nor DOS era. I'm more from the Windows XP and Windows 7 era and I was 5 years old (that was in the Year 2008) who I am used a Laptop (a Acer Aspire One A110).🙂

Nobody asks me but I want to tell it.😁

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On 2/22/2021 at 7:13 AM, codewar65 said:

640x480 is about all the VRAM on VERA can handle; and about what a 65x02 @ 8MHz can handle populating the VRAM in a timely manner.

Just a note: the preferred group term for the 6502 and its descendants is "65x". 

That would not only cover the MOS designs (6502, 65C02, 65816, etc) but the variants made for Commodore (6510, 8502), Atari (6507), and NES (Ricoh 2A03 - which adds sound and game controller polling, but removed the BCD mode).

So like we say "x86" to mean everything from the 8088 to the Intel Core i12, "65x" means "everything with a 6502 instruction set."

 

Edited by TomXP411
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3 hours ago, TomXP411 said:

Just a note: the preferred group term for the 6502 and its descendants is "65x". 

That would not only cover the MOS designs (6502, 65C02, 65816, etc) but the variants made for Commodore (6510, 8502), Atari (6507), and NES (Ricoh 2A03 - which adds sound and game controller polling, but removed the BCD mode).

So like we say "x86" to mean everything from the 8088 to the Intel Core i12, "65x" means "everything with a 6502 instruction set."

Though it seems pretty clear that we are going to be in the 65xx subset, unless a we get a 3rd party 65c816 daughterboard.

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