Raven. A homemade Atari-like computer

[luciodra]

Chapter strange video cards with 5429 and rj45.
Two pieces of news, one negative and one positive: the negative is that after turning on Raven, bang, smoke and smell of burning. The isa slot it's broken.
The positive thing is that changing the ISA slot to the old ET4000 Raven works. So maybe I just broke the first isa slot...

Oh dear

[agranlund]

It's a tad low resolution.. 640x480? 640x240?

Yeah I think it went all the way up to 640x480 (?)
But as I recall most games ran 320x200 or thereabout and probably at a blistering 20fps or so

Don't know an actual sane usecase other than there are plenty of PSOnes out there and it would be cool if someone desoldered GPU+Vram and used it for something

As far as I understand the GPU itself has a simple 32 bit host port for a cpu to communicate with and issue draw commands.
I believe/hope you can ignore the DMA channels and upload texture data through the host-port too.

It doesn't know anything about 3D so transforms has to be done on CPU and in the end ask the GPU to draw 2D triangles or quads, which it can do pretty quickly and even texture-map them (without perspective correction = the classic 'wobbly' texture issue on playstation1 games)
Also doesn't even have a Z-buffer so the programmer needs to sort primitives by their average Z and draw them back-to-front.
This causes plenty of per-face Z fighting issues, but who cares.. it was still mind blowing for a mid 90's home console.

"Perfect is the enemy of good"


But for Atari machines in general it feels like there must be an opportunity to use the ATW800/2 card to do some pretty neat stuff?
With the transputer having direct access to the framebuffer perhaps someone will experiment adding some more gpu-like features to it someday.
Sprite scaling/rotation, triangles and whatnot being drawn by transputer while the 68k is doing other things? Maybe even do the 3D transforms on the transputer side. (Though I don't have a card and have no idea about performance and practical viability of using it for those kinds of things )

[Mikerochip]

Yeah I think it went all the way up to 640x480 (?)

I did a quick check, and it seems to say, 24-bit colour, at 640x240 progressive, or 680x480 interlaced.

It *sounds* like you've almost got the schematics drawn out

I did, after looking closely, see that recent transputer board... has a transputer implemented in an fpga, is that right? (Using a tang nano 20k)

Emu68 is soon gonna have a PowerPC implementation, on the pi's second core! Not useful to us, just interesting.
That said... I wonder..

PiStorm '060 when??

The future is looking bright, for these old machines...

I guess, if someone was so inclined, they could implelement a bunch of similar "GPU" processors, in FPGA, on an ISA card.
MiSTer certainly has a bunch of them...
Not sure where I was going with that though. But. Anyhow.

[Darklord]

But for Atari machines in general it feels like there must be an opportunity to use the ATW800/2 card to do some pretty neat stuff?
With the transputer having direct access to the framebuffer perhaps someone will experiment adding some more gpu-like features to it someday.
Sprite scaling/rotation, triangles and whatnot being drawn by transputer while the 68k is doing other things? Maybe even do the 3D transforms on the transputer side. (Though I don't have a card and have no idea about performance and practical viability of using it for those kinds of things )

You saw the DOOM demo running on the ATW800/2, right?

[Mikerochip]

I certainly hadn't!
Running is a bit of a stretch It's a great proof of concept, to start with.

I wonder, though, if it wouldn't be faster on the Raven!

One of the 68060 Amiga ports, on the A1200 with a 68060 accelerator card, runs at aroun 35FPS !!

[PhilC]

I certainly hadn't!
Running is a bit of a stretch It's a great proof of concept, to start with.

I wonder, though, if it wouldn't be faster on the Raven!

One of the 68060 Amiga ports, on the A1200 with a 68060 accelerator card, runs at aroun 35FPS !!

The Raven runs Doom quite nicely actually and will even run Quake, albeit mine is running at 100mhz.

[mrbombermillzy]

Im not really a 3D math guru, so this may be naive thinking but...

Just before 3DFX folded and was absorbed into Nvidia, their SW engineers released some last ditch OpenGL drivers which incorporated a hidden surface removal (HSR) system which whist buggy - improved render speed significantly enough to make an improvement.

I wonder if a more downscaled version of this can be used to speed rendering for the Raven Doom (or better still Quake) build?

Possibly this could be 'injected' inbetween rendering processes rather than having to change the structure of the whole SW rendering system itself.

[Darklord]

Running is a bit of a stretch It's a great proof of concept, to start with.

That's why I said "demo".

I did set it up on my ATW800/2 card here in my Mega STe and it certainly
looked and ran fantastic.

[agranlund]

Running is a bit of a stretch It's a great proof of concept, to start with.

That's why I said "demo".

I did set it up on my ATW800/2 card here in my Mega STe and it certainly
looked and ran fantastic.

That's really cool!
And not bad considering it's also upscaling the picture according to the youtube description.

[agranlund]

Some minor svga driver tweaks in latest:

Code: Select all

rvnova: option to scale dac value
rvnova: fixed potential bug with blitter fillpattern address

I noticed that blitter fillpattern worked by luck rather than intentional so fixed that.
Or rather, the address as given to blitter was 2MB too high and on my cards that basically just wrapped and ended up correct anyway but I think @PhilC had some weirdness with fillpatterns on a card and maybe it was due to this.

The other change is a new option in rvga.inf which allows you to scale the DAC values in case it's too "hot" and washes out / clips on modern displays.
There's nothing fancy, it's just scaling the dac palette values so you'll end up loosing precision by scaling down.
An actual hardware between card and display which is capable of adjusting the analogue gain would surely be better.

All my cards are displaying as they should on my particular LCD monitor except for a WD90C33 which produce that washed out image with clipped highlights. That prompted me to add this setting and "dacscale = 196" makes the monitor happy.

I'm wondering if it's due to ageing components and a recap would help, or if the card in question is just not that bothered about being accurate with the 0.7V range. I'm guessing a CRT didn't really care too much and just fired harder rather than clipping like a modern device?
Perhaps also, the fact that color0 is white is throwing the black/white level calibration off on some modern digital devices.