32768 color dual Shifter ST mod - schematics lost?

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Smonson
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Re: 32768 color dual Shifter ST mod - schematics lost?

Post by Smonson »

mrbombermillzy wrote: Wed Dec 08, 2021 7:50 pm Forgive me, as I'm not a HW guy, but wouldn't what you just explained then create a physical 18-bit palette?
Yes. If it wasn't for the fact that the palette writes are only 16 bits wide they could have made the mod support 18-bit colour. Actually they could have gone up to 5-6-5 format with no extra work, which is a real format used on several video cards back in the old days. Our eyes are more sensitive to green than red or blue so it makes sense to chuck an extra bit at it.

Of the 6 bits per colour coming out of the two shifters, one will always be zero so it would just be left unconnected.
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Smonson
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Re: 32768 color dual Shifter ST mod - schematics lost?

Post by Smonson »

If anyone wants to see more colours on the HDMI mod, we can easily bump it up to 8bpp (which is the native HDMI colour depth).
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Darklord
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Re: 32768 color dual Shifter ST mod - schematics lost?

Post by Darklord »

I'm always amazed how so many times a seemingly random comment or just something
said from left field, even from a totally different tangent, will cause a chain of events
that leads to a great idea. :yay:
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Icky
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Re: 32768 color dual Shifter ST mod - schematics lost?

Post by Icky »

Smonson wrote: Thu Dec 09, 2021 1:01 am If anyone wants to see more colours on the HDMI mod, we can easily bump it up to 8bpp (which is the native HDMI colour depth).
Have been following this thread and was waiting on your thoughts @Smonson for the HDMI shifter. This seems to be the best platform to tinker and try these improvements out on as it has a large FPGA for space of more than one shifter and also provide any plumbing necessary. That said we need to work in steps to get the shifter completed then trial your 256 node and the 8bpp option. I see the shifter recreation as opening the door to this world.
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JezC
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Re: 32768 color dual Shifter ST mod - schematics lost?

Post by JezC »

@Icky @Smonson I'm still hoping that some version of the HDMI Shifter will be available soon...I'd personally settle for something that runs well-behaved GEM apps as a starting point (maybe with the option to upgrade/update the FPGA image in the future) - if only to help support this great development.

I know the issues arising from the chip shortages (fighting with those almost every day at work...which is somewhat tiresome after over 12 months of doing so!) so it won't be imminent...but maybe some pre-order/interest list would help gauge the level of interest (and exactly what degree of compatibility people are expecting).

Obviously, there's a likelihood that adding some of these enhancements might be at the expense of full compatibility with the original Shifter anyway!

The other (selfish) reason for the interest is that the Shifter is proving to be one of the more difficult parts to source for the H4/H5 boards...possibly only second to the Blitter (which I've got a couple of from the @exxos store previously).
But - while most s/w will work without the Blitter, we're pretty much dead in the water without the Shifter (or an alternative)...

Anyway, delighted with the efforts you are all putting into this (and other projects) & happy to do my best to support them however I can!
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Re: 32768 color dual Shifter ST mod - schematics lost?

Post by Icky »

@JezC - at the moment there are delays as you mention on chip shortages. I do have a stash of 5 chips left. I had been having issues with my board assembler who has about 5 boards in flux being on radio silence, until last week :) and am still in the middle of a protracted house move.

So am hoping after Christmas I should have a bunch of boards and time to bring this project back online with being in my new house. Fingers crossed.
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mrbombermillzy
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Re: 32768 color dual Shifter ST mod - schematics lost?

Post by mrbombermillzy »

Ok. Well @sporniket and @Smonson ...

Thank you for your valued input.

Just a thought for the future:

If it gets to that stage where someone can realise the circuit, then if any time anyone can be so kind as to build me a circuit for one of these, shifterless even (I will be prepared to pay of course) then I would be more than happy to re-purpose my 'Shifter Killer' routines from the TT. Any relevant data gleaned there can be fed back to the HDMI Shifter project for compatibility purposes (if that's a needed thing?)
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Re: 32768 color dual Shifter ST mod - schematics lost?

Post by Smonson »

mrbombermillzy wrote: Thu Dec 09, 2021 9:01 am I would be more than happy to re-purpose my 'Shifter Killer' routines from the TT. Any relevant data gleaned there can be fed back to the HDMI Shifter project for compatibility purposes (if that's a needed thing?)
Yes please, that is definitely needed. What we need for test cases is a short sequence of code (one scanline or so) that twiddles the shifter in some advanced way and causes it to output data differently. {Closure} is doing this sort of thing but we don't have enough info to build a test case.
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mrbombermillzy
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Re: 32768 color dual Shifter ST mod - schematics lost?

Post by mrbombermillzy »

Smonson wrote: Fri Dec 10, 2021 11:47 pm
mrbombermillzy wrote: Thu Dec 09, 2021 9:01 am I would be more than happy to re-purpose my 'Shifter Killer' routines from the TT. Any relevant data gleaned there can be fed back to the HDMI Shifter project for compatibility purposes (if that's a needed thing?)
Yes please, that is definitely needed. What we need for test cases is a short sequence of code (one scanline or so) that twiddles the shifter in some advanced way and causes it to output data differently. {Closure} is doing this sort of thing but we don't have enough info to build a test case.
Well, probably best to explain from the beginning, so you know where Im coming from...

The routines I am working on (1st display method) are actually code for high colour static display output for 8bpp palette machines (i.e the TT, but will likely transfer to F030, A1200, etc). These routines are similar to Spectrum512/Quantum but with extra colour write avoidance code. The more advanced stuff (2nd display method) is similar, but almost like a poor mans MJPG codec for the use of action games with a similar high colour content available (IF I can pull it off and don't find any minor detail, of many, that becomes a major show stopper in the meantime).

I've blogged the initial testing here: https://www.exxosforum.co.uk/forum/viewt ... =18&t=3936 but things have slowly advanced a bit more since then (nowhere near getting complete however, but some of the errors in the explanations in that post have been corrected or better ways of doing things have been realised) and more importantly, I believe the end goals of both display methods can be achieved, especially if boosters are included in the mix with display method 2.

Anyhow, (finally!) to my point... a 'side effect' of this research is some crazy experiments on the poor TT shifter to try and realise the above end goal.

I have several simple sync locked test programs, write limit stress tests, etc; mainly visual aids as to the working of the shifter essentially.

What I can attempt to do is transfer these mainly visualisation tests to an ST shifter. But is the one you are creating an exact copy of one of the ST/F/Mega shifters or will it be an 'augmented copy' i.e. fully 100% compatible, but with extra features? Let me know any differences and I will factor that in.

While I have pretty much done my own thing with the TT shifter because of lack of detailed info (wish the Atari Profibuch had been translated! lol), the ST one has been far more thoroughly documented.

As you have already mentioned, Troed is one of the major sources of accurate detailed information for the workings of the ST shifter. I'm sure he will have far more knowledge than I do (having never actually coded for the ST yet! :o ), but I would maybe be able to chip in if no one better is available...happy to help if I can at all.

One last thing to note... If you DO need/want my help, my work for this will be done/tested from my end on the only ST I own, which is a Mega2 with 4Mb. Now I'm not sure if it either needs attention, as 'Closure' displays graphical artifacts, or perhaps its the fact that the Mega has its own special 'close to but not quite the same as' an STFM 8Mhz osc. Perhaps @troed knows if its the demo not suitable for the slightly out clock, or my machine that needs attention! :lol:

P.S. Sorry about the overly long post guys. Just thought it best to explain everything properly to ascertain whether what I can contribute will be useful/relevant at all.

Perhaps any further correspondence can be done via PM to avoid completely derailing this interesting topic? :)
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sporniket
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Re: 32768 color dual Shifter ST mod - schematics lost?

Post by sporniket »

I got some time slice to make a schematic from my doodle. Comments are welcome, of course. EDIT : and a last minute screw, CS2 = CS or R/W of course... will fix that now.

rgb565-experiment--2021-12-14.png
rgb565-experiment--2021-12-14.png (210.81 KiB) Viewed 2854 times

ha, seems the image is zoomed out, here is a pdf version. The sheet is A3-sized, but I took care to put nothing crossing the middle line, so it's safe to print into two A4-sized sheets.

EDIT 2 : fixed version

rgb565-experiment.pdf
(82.49 KiB) Downloaded 113 times
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