PCI Express video

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Peter
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Re: PCI Express video

Postby Peter » Wed Feb 19, 2020 11:29 am

Pr0f wrote:I have been thinking about this for some time too, and trying to figure out a way of getting QL video out of an HDMI socket.

There are several hurdles and problems, but some thoughts below:

1) QL screen memory use is a little strange in the layout - so that tends to rule out all but a large CPLD or FPGA to do the video so that compatibility is maintained

[...]

If you go FPGA anyway, HDMI signals can be generated. The obstacle here is to solder modern BGA chips as a hobbyist, and all the ground work to move from a classic chip to a modern one with more pins and more highspeed considerations. But in general I see this closer to realism than other ideas mentioned on the forum.

Since every modern FPGA suitable for HDMI has enough space to include a CPU, my question is: Would you still want the CPU outside the graphics chip, and why?


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Pr0f
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Re: PCI Express video

Postby Pr0f » Wed Feb 19, 2020 11:48 am

Peter wrote:
Pr0f wrote:I have been thinking about this for some time too, and trying to figure out a way of getting QL video out of an HDMI socket.

There are several hurdles and problems, but some thoughts below:

1) QL screen memory use is a little strange in the layout - so that tends to rule out all but a large CPLD or FPGA to do the video so that compatibility is maintained

[...]

If you go FPGA anyway, HDMI signals can be generated. The obstacle here is to solder modern BGA chips as a hobbyist, and all the ground work to move from a classic chip to a modern one with more pins and more highspeed considerations. But in general I see this closer to realism than other ideas mentioned on the forum.

Since every modern FPGA suitable for HDMI has enough space to include a CPU, my question is: Would you still want the CPU outside the graphics chip, and why?


That all boils down to purpose again. I was thinking about this from the possiblity of making a QL from the ground up, but at the same time breaking this down into modules that may in their own write become plug in cards for QL's bases on the BBQL or Gold/SGC and Aurora - as there is still some appetite for these.

I've identified some possible candidates:

1) Serial port card - fast and reliable serial ports with full modem control signals
2) Video card with support for new monitors
3) USB devices - this seems the most difficult because it would involve 2 layers of driver to support multiple device types (printer, keyboard, joystick, mouse, serial port, parallel port, flash stick, disk drive)


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Peter
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Re: PCI Express video

Postby Peter » Wed Feb 19, 2020 12:29 pm

Peter wrote:Since every modern FPGA suitable for HDMI has enough space to include a CPU, my question is: Would you still want the CPU outside the graphics chip, and why?

How about a reply on this?


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Pr0f
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Re: PCI Express video

Postby Pr0f » Wed Feb 19, 2020 1:56 pm

Peter wrote:
Peter wrote:Since every modern FPGA suitable for HDMI has enough space to include a CPU, my question is: Would you still want the CPU outside the graphics chip, and why?

How about a reply on this?


I thought I had covered this with the explanation that what was being considered was a circuit / module that could be applied to a recreation or as an add on card to existing bbql - so FPGA with the CPU on board doesn't really fit the requirement if it's just a video add on for existing hardware.

I suspect the logic payload I am thinking about may even fit into a MACH4256, with a readily available chip to provide digital to hdmi conversion.

You have already provided CPU+Graphics on an FPGA by providing the excellent Q68, so I didn't see any reason to repeat that work.


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Peter
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Re: PCI Express video

Postby Peter » Wed Feb 19, 2020 3:20 pm

Pr0f wrote:I thought I had covered this with the explanation that what was being considered was a circuit / module that could be applied to a recreation or as an add on card to existing bbql - so FPGA with the CPU on board doesn't really fit the requirement if it's just a video add on for existing hardware.

Thanks for the clarification - for me it was not obvious you'd still go for separate graphics if it means lots of unused FPGA space.

Pr0f wrote:I suspect the logic payload I am thinking about may even fit into a MACH4256, with a readily available chip to provide digital to hdmi conversion.

Just that the MACH4256 costs more than twice the LFE5U-12F, plus the extra costs/space for the external HDMI chip and the external CPU.

I'm not saying a modular system is a bad idea. I was just curious if you still want it once you are aware of the "resource waste". Would all your potential modules fit into a QL case?


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Pr0f
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Re: PCI Express video

Postby Pr0f » Wed Feb 19, 2020 5:47 pm

Pr0f wrote:I suspect the logic payload I am thinking about may even fit into a MACH4256, with a readily available chip to provide digital to hdmi conversion.


Peter wrote:Just that the MACH4256 costs more than twice the LFE5U-12F, plus the extra costs/space for the external HDMI chip and the external CPU.

I'm not saying a modular system is a bad idea. I was just curious if you still want it once you are aware of the "resource waste". Would all your potential modules fit into a QL case?


I am on target to fit into the QL case at the moment, but the design going into the QL case was just on the one board, the circuit layout is where the modular nature is, the idea being that individual sections could be taken out and turned into a euro board for fitting in a backplane / QL expansion slot. All the ROMS that would have been on separate boards for instance are all in one 29F040 Flash ROM, along with the base OS so much saving of space there.

I have been playing around with both an FPGA or a CPLD for video generation - I already had the MACH device for another project - it still might change.



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