Beyond Super Gold Card

A place to discuss general QL issues.
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tofro
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Re: Beyond Super Gold Card

Postby tofro » Thu Nov 14, 2019 9:19 am

Peter,

well, it's not only the screen refresh for high color display that slows the Q68 - Also, the poor CPU has lots more to do to initially fill the screen with information.

Setting a pixel in MODE 4 requires to set two bits in screen memory.
In high-color modes, you have to set two bytes.

Scrolling the whole screen requires to move 32k bytes around in 512x256 in MODE 4/8.
Doing effectively the same thing in even the simplest high-color mode (DISP_MODE 6) moves 10 times the memory,
32 times the amount in DISP_MODE 3, 48 times in DISP_MODE 7.

Don't get me wrong - I'm not claiming the Q68 is slow (it is blazingly fast for a 68000) - But handling a high-color display requires brute, raw CPU power or support from a GPU. There's a reason why Amigas and Atari STs (with even inferior graphics to the Q68) had to have custom chips to help them juggle with high-res/high-color screens. What the Q68 does in terms of graphics (sound as well), is very probably scratching the limits of a non-hardware-accelerated graphics system (and it also shows there are more than enough applications that don't even require this speed - were talking games here).

This is why I like DISP_MODE 6 on the Q68 - It is a good compromise between display quality and achievable performance.

I also like the Aurora modes if you want to be even faster - I personally don't care so much about color depth, even find pixelized 8-bit color modes quite appealing on a retro machine. A mix between DISP_MODE 6 and 5 (512x384 with 8-bit color) could even be my favorite mode if it were available.

But these are personal preferences - I think the main challenge with retro machines is their limits. If these limits weren't present, the Q68 (or all QL-alikes) would just be mediocre modern computers. An unlimited-speed QL would be very, very boring.

(I have an Amiga 600, with 128kB of memory and a Vampire CPU - blazingly fast. It doesn't see much use)


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Peter
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Re: Beyond Super Gold Card

Postby Peter » Thu Nov 14, 2019 9:25 am

Derek_Stewart wrote:Could we have this type of display on the QL, with the same speed as the Q68.

Technically it is possible, if I move on to a new generation FPGA. I have already started to work toward a solution.
I'm not sure how to deal with HDMI licensing. It seems that other FPGA projects just use HDMI connectors without paying anything, so maybe we can do the same.
Otherwise, I'd have to use a DVI connector, and then let people use DVI to HDMI cables. Which would be ridiculous, because the signals are the same, and it justs wastes space on the board.


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vanpeebles
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Re: Beyond Super Gold Card

Postby vanpeebles » Thu Nov 14, 2019 9:52 am

Could you use a pi zero just for hdmi? I think that's how a lot of projects get round the licensing?


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Peter
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Re: Beyond Super Gold Card

Postby Peter » Thu Nov 14, 2019 9:55 am

tofro wrote:well, it's not only the screen refresh for high color display that slows the Q68 - Also, the poor CPU has lots more to do to initially fill the screen with information.

Yes I'm aware, but the initial fill (or things like moving windows) is not what I think bugs users like Fabrizio most. I have also heard from another user who is only concerned about the 56% loss of overall speed in the highest resolution, and otherwise okay with display speed. Let's see how Fabrizio perceives 1024x768 in 4 colours - if that is already too sluggish for folks like him, it makes little sense to only add separate video memory.

All this reminds me of my initial plan to hide the memory intensive display modes altogether. I have always warned about them, and the manual warns about them, but in the end people just use and feel annoyed.


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Peter
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Re: Beyond Super Gold Card

Postby Peter » Thu Nov 14, 2019 10:07 am

vanpeebles wrote:Could you use a pi zero just for hdmi? I think that's how a lot of projects get round the licensing?

No, the Raspi Zero has no sufficently fast interface to receive the Q68 video data. Note that we are talking about 1.5 MB screen memory, a completely different league than typical retro computers.

Also: The additional board space consumption for a DVI connector instead of HDMI is much smaller than a Raspi Zero and costs 3 times less.

Another option is a display port connector, but that could create confusion as it would work only with HDMI monitors by a suitable cable, not with actual display port monitors.


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Peter
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Re: Beyond Super Gold Card

Postby Peter » Thu Nov 14, 2019 10:56 am

tofro wrote:But these are personal preferences - I think the main challenge with retro machines is their limits.

The issue here might be that, surprisingly, some SMSQ/E users don't see it as pure retro computing, but still actually do some of their work on native hardware. Could have to do with the fact that at design time, the Q60 was so fast that it even outperformed contemporary PCs in some aspects. For example video memory transfer rates. And the 68060 wasn't too bad versus Pentium either. Sales start was too late to directly compete with non-emulation PCs, but stil...

The Q68 is sort of a compromise between pure QL retro computing and the Q60, and it does not play either role perfectly well.

On the other hand, demand for the Q68 has widely exceeded all expectations, and this seems related to 68000 compatibility. With a 68060, or even a FPGA equivalent like Vampire, some very old software would not have worked, probably losing retro users.


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Peter
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Re: Beyond Super Gold Card

Postby Peter » Thu Nov 14, 2019 12:02 pm

By the way, I'm all but sure that HDMI is a good idea! I have a number of monitors with only VGA input. And all my HDMI ones also have VGA! Many brandnew ones still have VGA, very easy to get. Definitely no problem yet, if one takes a little care. For myself, HDMI would be a clear disadvantage! Even more so, as I prefer the 4:3 screen dimensions of the QL and Q60 times, not widescreen.

It's so easy to cry that an interface is "obsolete" expecting supply shortages which are not yet here. But the actual situation is that retro users usually have monitors, and creating a need to dump them might not always be clever. An adator from VGA to HDMI is a matter of a few Euro, a new monitor costs much more.


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dilwyn
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Re: Beyond Super Gold Card

Postby dilwyn » Thu Nov 14, 2019 12:19 pm

Watching this discussion with interest, even though I'm not (yet!) a Q68 user (been so busy this year I've barely had time to touch a QL). Thanks goodness for QPC2!

I'm definitely of the opinion that some form of super-duper-gold-card is needed to keep the good old bbql going. While Vitaly (Tetroid) is able to produce Super Gold Card clones, that's fine. But we are seeing a steady trickle of new or returning QL users appearing on here and the QL-related groups on Facebook, so there would be a ready market for one - Peter may well find that the demand exceeds his expectations like the Q68 did if he decides he has the time and energy to design one. Definitely room for both stand-alone Q68-style systems, plus a plug-in derivative to keep the bbql going.

So, please keep the discussion going and help Peter decide which way his thoughts should go.


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vanpeebles
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Re: Beyond Super Gold Card

Postby vanpeebles » Thu Nov 14, 2019 12:21 pm

Great to hear that the Q68 did well :)


stephen_usher
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Re: Beyond Super Gold Card

Postby stephen_usher » Thu Nov 14, 2019 2:24 pm

vanpeebles wrote:Could you use a pi zero just for hdmi? I think that's how a lot of projects get round the licensing?


Not using the bitmapped graphics the QL uses as there's no shared memory. Unfortunately QDOS doesn't have a display abstraction layer, such as the Atari ST has with GEM, so there's no way of sending commands over the restrictive data bus provided by any GPIO interface and asking the Pi to render it natively.

I don't know how the pointer environment works but I guess that has it's own abstraction layer which may be usable over such an interface but the normal bitmapped graphics is right out of the question. (The closest you could get would be to have a graphics sub-system like the MSX one where you have to tell the TI graphics chip what bytes to write at what graphics location.)



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