[Oberon] FPGA - Colour Support
joerg.straube at iaeth.ch
Mon Oct 16 11:49:37 CEST 2017
If we want to stick wth 1 MB, here some calculations
1024 x 768, 1 BPP = 96 KB, code&data = ~920 KB <— standard config
800 x 600, 2 BPP =117 KB, code&data = ~900 KB
1024 x 768, 2 BPP =192 KB, code&data = ~830 KB
800 x 600, 4 BPP =234 KB, code&data = ~790 KB
The last config would reserve roughly 1/4 of the memory for the screen. I would not go higher to still have a decent amount of memory left for code & data.
BTW: The nice thing with 800x600, we could use a pixel clock of 50 MHz :-)
> Am 16.10.2017 um 10:00 schrieb Jörg <joerg.straube at iaeth.ch>:
> With the resolution of 1024x768 currently used by Project Oberon
> 8 BPP needs 768 KB memory
> 16 BPP needs 1.5 MB (more than the whole system uses today..)
> You definitely need more than today’s 1MB RAM :-)
> With this amount of memory to be moved, stealing clock cycles from the CPU might get critical. So, if you want to go in this direction, you might think of introducing separate RAM for graphics so the HW driver can access video memory without stealing CPU cycles.
> I was more thinking in the direction of 2 MB common memory (no separate video RAM) and 4 BPP (=384 KB)
>> Am 08.10.2017 um 18:50 schrieb Skulski, Wojciech <skulski at pas.rochester.edu>:
>>> Full ACK here. I will likely port Project Oberon to ARM32 Linux. So I
>>> will write a 32bpp display driver anyway. 8bpp would be nearly the same.
>> Note that some ARM boards use 16-bit color. Here is an example. This is the schematic used by BeagleBone Black, which I copied verbatim into my MicroBone. They use some sort of "industry standard" color mapping scheme which is good for driving LCD panels. That's why they call these wires LCD... These LCD wires are then converted to HDMI, using a hardware converter shown in the schematic. I just copied all this into my design in order to stay 100% compatible with existing hardware, as you pointed out.
>> The BBB display driver must exist and it must have taken this color scheme into account. I would bet that the mapping from a general 32bpp color to 16bpp color must have been somehow implemented. I just want to bring this into your consideration.
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> Oberon at lists.inf.ethz.ch mailing list for ETH Oberon and related systems
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