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Re: True 16MHz Mode

Posted: Sun May 26, 2019 11:52 am
by exxos
Interesting.. RAM access being 199% is likely the cause. Try adding something like 2.2k pull up on dtack and see if it comes up to 200%.

Re: True 16MHz Mode

Posted: Sun May 26, 2019 2:32 pm
by Smonson
exxos wrote:
Sun May 05, 2019 11:19 am
640x200x16 ;)
What we need now is a shifter which can make use of the extra bandwidth ;)
What needs to be done to get the HDMI mod working at 16MHz? I take it you are feeding the stock shifter with 64MHz to get it to output 32MHz to the MMU, same as Troed? I can give you a firmware file that outputs 32MHz instead of 16MHz with no hardware changes, if you like.

256-colour mode is supported in the mod board since about 9 months ago, but I've only been able to test it at 160x200 because I don't have a double-speed machine, and my mod doesn't want to work on Troed's machine.

Re: True 16MHz Mode

Posted: Sun May 26, 2019 2:39 pm
by Cyprian
Smonson wrote:
Sun May 26, 2019 2:32 pm
256-colour mode is supported in the mod board since about 9 months ago, but I've only been able to test it at 160x200 because I don't have a double-speed machine, and my mod doesn't want to work on Troed's machine.
planar or chunky?
and in what address range palette registers are?

Re: True 16MHz Mode

Posted: Sun May 26, 2019 2:43 pm
by exxos
Smonson wrote:
Sun May 26, 2019 2:32 pm
What needs to be done to get the HDMI mod working at 16MHz? I take it you are feeding the stock shifter with 64MHz to get it to output 32MHz to the MMU, same as Troed?
No.. The shifter is still running at stock speed..
Smonson wrote:
Sun May 26, 2019 2:32 pm
256-colour mode is supported in the mod board since about 9 months ago, but I've only been able to test it at 160x200 because I don't have a double-speed machine, and my mod doesn't want to work on Troed's machine.
oh cool, What I will do is build up a second remake board on the new batch and send it to you (but this will be some time away yet) .. then you can develop the extra video modes in your shifter :) We literally have 200% bandwidth to play with now.

Re: True 16MHz Mode

Posted: Sun May 26, 2019 3:26 pm
by Smonson
I don't have a donor machine (yet) - the chipset ICs on my ST are the QFP type. Anyway, I'm not very good at all the high-speed analogue stuff.

But I can make the HDMI mod board do whatever you need!
Cyprian wrote:
Sun May 26, 2019 2:39 pm
planar or chunky?
It's one byte per pixel, although there's enough room in the resolution register to add another 16,382 more modes if someone wants planes.

I used a free shifter register for the upper 4 bits of the palette index, can't remember what address it was in ram off the top of my head. I think the TT has the same scheme.

Re: True 16MHz Mode

Posted: Sun May 26, 2019 4:09 pm
by Icky
exxos wrote:
Sun May 26, 2019 2:43 pm
Smonson wrote:
Sun May 26, 2019 2:32 pm
What needs to be done to get the HDMI mod working at 16MHz? I take it you are feeding the stock shifter with 64MHz to get it to output 32MHz to the MMU, same as Troed?
No.. The shifter is still running at stock speed..
Smonson wrote:
Sun May 26, 2019 2:32 pm
256-colour mode is supported in the mod board since about 9 months ago, but I've only been able to test it at 160x200 because I don't have a double-speed machine, and my mod doesn't want to work on Troed's machine.
oh cool, What I will do is build up a second remake board on the new batch and send it to you (but this will be some time away yet) .. then you can develop the extra video modes in your shifter :) We literally have 200% bandwidth to play with now.
Or another option is I get the current STF Remake that I am slowly building built up with the 16MHz mode and send to Smonson?

Re: True 16MHz Mode

Posted: Sun May 26, 2019 4:29 pm
by exxos
Icky wrote:
Sun May 26, 2019 4:09 pm
Or another option is I get the current STF Remake that I am slowly building built up with the 16MHz mode and send to Smonson?
That would speed up the shifter development no end.. But don't you need it tho?

Re: True 16MHz Mode

Posted: Mon May 27, 2019 9:03 am
by Smonson
I don't think you should go that far. The 256-colour mode is definitely working, so I'm not sure there's much other work to do, apart from hooking the clock up.

Re: True 16MHz Mode

Posted: Mon May 27, 2019 10:19 am
by exxos
Smonson wrote:
Mon May 27, 2019 9:03 am
I don't think you should go that far. The 256-colour mode is definitely working, so I'm not sure there's much other work to do, apart from hooking the clock up.
Medium res with 16 colours ;). Would be cool to ultimately get 640x400x16 as well :)

Re: True 16MHz Mode

Posted: Mon May 27, 2019 11:45 am
by Smonson
exxos wrote:
Mon May 27, 2019 10:19 am
Medium res with 16 colours ;). Would be cool to ultimately get 640x400x16 as well :)
Med res with 16 colours is just mode 0 at double speed, and 640x400x16 is mode 0 at quadruple the speed, which is pushing your luck a bit :lol: