Raven. A homemade Atari-like computer

[PhilC]

Oh wow, I tested my second GD5426 card and the results are really interesting.

Gembench in 1024x768 256 colors.

Card1 (Diamond Speedstar Pro)
Blitting: 2173
VDI scroll: 1800

Card2 (FastMax by Vidtech Microsystems)
Blitting: 1280
VDI scroll: 1143

The slower one has only 10ns slower ram and I doubt that can responsible for such a huge difference?
Feels likely that the Diamond bios is configuring the chipset better and/or much more aggressive by default.

That sounds interesting. I'm wondering if I try a different bios on this 5429 whether I can speed it up. The Diamond Speedstar Pro also uses the same GPU.

[agranlund]

My Diamond Speedstar 24X (Western Digital WD90C31) scores this with hardware blitting in 1024x768x8bpp
Blitting: 2022
VDI scroll: 1628

Just a smidge lower than the Diamond Speedstar Pro (Cirrus Logic GD5426)
That WD90C31 has a bit more interesting graphics engine though, it can do lines and trapezoids as well.

[PhilC]

Just looking at the results from my 5429 and it's slower using the same tests. I suspect that the driver will want optimising for this card.

When running this card on Win98, there is a separate driver for 29,30 and 34 GPUs, so the clue maybe there.

I'll have a read of the datasheet a bit later on.

PXL_20250819_093323872.NIGHT.jpg (525.53 KiB) Viewed 1015 times

[mrbombermillzy]

@agranlund and @PhilC you two are on fire with this! Great stuff going on right here!

That auto switching to run Tyrian is some cool trick.

Perhaps one day, some of this awesome work can transition over to the mere mortals with 'regular' STs/ISA cards.

[Cyprian]

Just looking at the results from my 5429 and it's slower using the same tests. I suspect that the driver will want optimising for this card.

When running this card on Win98, there is a separate driver for 29,30 and 34 GPUs, so the clue maybe there.

I'll have a read of the datasheet a bit later on.

PXL_20250819_093323872.NIGHT.jpg

cool.
I wonder how it looks compared to Falcon and TOS 4.04

@agranlund well done. Thanks. Would it be possible to use your Cirrus Logic GD5426 driver on Mega STE with Nova adpter?

[agranlund]

Just looking at the results from my 5429 and it's slower using the same tests. I suspect that the driver will want optimising for this card.

That looks suspicously similar to the slower of my two GD5426 cards.

I'm not at all surprised the Diamond is faster than my other "lesser" Vidtech card even with the same GPU.
The likelyhood of that brand picking fast components and having aggressively tuned bios for the particular card is quite high, but the difference here is just a bit too much.

Memory clock can differ almost 2x from lowest to highest setting, and the width can be set at 8, 16 or 32bit at the manufacturers leisure.
So my bet is on a difference in settings applied by their respective bioses.
Wether that would be intentional, or set badly in error due to some x86 emulation issue I don't know.

But I think I'll have to first print out and compare the interesting config registers for both cards and see what they are actually set to.

Hmm, I wish I had a 486 retro machine so I could compare the cards in Winbench -- as well as all the other fun you can have with a 486

[PhilC]

@agranlund only 486 I have is a 486slc, so not a real one but if it's any good for your needs?

[agranlund]

@agranlund well done. Thanks. Would it be possible to use your Cirrus Logic GD5426 driver on Mega STE with Nova adpter?

Thank you Cyprian!

For the time being it's only compatible with Raven.
It makes it much less painful and quite easy and fun to implement, is the only reason really.

I don't think it would be that much effort for someone to make it work on other very fast machines, but getting it to run on 68000 would take quite a bit more effort I think. There you'd want to do card initialisation and setting of graphics modes manually rather than calling onto vgabios to do it for you.

[agranlund]

So it turns out that yes, true to form Diamond is more aggressive with its settings.

Code: Select all

Diamond Speedstar Pro:
 mclk: 62.6 mhz
 dram: 50 mhz, 32bit, extended RAS, fpm on
 fifo: 16, threshold: 1

Code: Select all

Vidtech Fastmax:
 mclk: 50.1 mhz
 dram: 37 mhz, 32bit, standard RAS, fpm on
 fifo: 8, threshold: 2

62.6mhz is well above what Cirrus rates the GD5426, and even a bit over that of the GD5429
(50mhz for GD5426 and 60mhz for GD5429)

Dram is also set faster and they set a larger fifo by default.

Probably the Vidtech settings are sensible in that they keep safe and well inside specs, or maybe they had no interest or time to experiment with whatever over-spec settings they could get away with. It's also using worse drams.
I'm going to see what happens if I push that Vidtech a bit.

[PhilC]

@agranlund how did you find that out?

I've got a Diamond 5429 coming from the US, so would be good to be able to do the comparison.