Raven. A homemade Atari-like computer

[agranlund]

I got a W32i with working interleaved mode and that certainly boosts the internal vram bandwidth.
How much practical difference this makes on an Atari is questionable but I can see this being a big deal on PC back in the day, where pretty much everything automatically took advantage of 2D hardware acceleration and on-card caching of sprites thanks to Windows and DirectDraw.


Bandwidth:
Mach32 vs W32i (interleaved) vs W32i (non-interleaved)
Video move shows a significant difference in vram-to-vram copy speed over the W32i with interleaving disabled.

Kronos_RAM_Mach32.jpg (54.64 KiB) Viewed 408 times

VDI operations:
Mach32 vs W32i (interleaved) vs W32i (non-interleaved)
We can see that the Mach32 is accelerating more operations compared to w32i.

Kronos_VDI_Mach32.jpg (55.15 KiB) Viewed 408 times

Gembench W32i (interleaved) vs W32i (non-interleaved)

W32i-interleaved__W32i-standard_hires.jpg (99.66 KiB) Viewed 408 times

Gembench Mach32 vs W32i (non-interleaved)
We see the Mach32 driver taking advantage of more accelerants here.

Mach32__W32i-standard_hires.jpg (45.31 KiB) Viewed 408 times

And as an interesting experiment, if we run the test on a lower resolution then the difference becomes minimal and the non-interleaved W32i test is almost the same speed as the interleaved one.
My best guess is that the card is nowhere near starved for vram bandwidth at the slow pixel clock needed for this resolution, together with the tiny area of graphics that Gembench is using for blit related tests.

W32i-interleaved__W32i-standard_lores.jpg (74.99 KiB) Viewed 408 times

[PhilC]

@agranlund was that using the W32i program you sent me? The blitter scores are so much quicker

[agranlund]

@agranlund was that using the W32i program you sent me? The blitter scores are so much quicker

Yep the same program (and a card that is wired up to support interleaved mode. mine has 16 pieces of 45ns ram chips)
I'll integrate the interleave-enable code in the bios and add an option for it in the menu.

[PhilC]

@agranlund was that using the W32i program you sent me? The blitter scores are so much quicker

Yep the same program (and a card that is wired up to support interleaved mode. mine has 16 pieces of 45ns ram chips)
I'll integrate the interleave-enable code in the bios and add an option for it in the menu.

Ok, that definitely doesn't work for mine but I do have another W32i card on its way, already with 2mb ram, so hopefully this one will do.

[PhilC]

BTW, this looks an interesting project

http://www.alexandrugroza.ro/microelect ... index.html

If my other W32 card works, I might try building one of these using the current one as a donor board.

[agranlund]

Updated the release package:
https://github.com/agranlund/raven/rele ... .A1.latest

20250620
rom: ckbd support
rom: eiffel key-repeat fix
rom: autorun srec programs after upload
firmware: (ckbd) added ckbd firmware binary
firmware: (nessi) reversed order of ram slots
rvbios: ET4000/W32i memory interleave setting
rvnova: ET4000/W32i memory interleave support

@dml , this nessi firmware should be a good match for your huge cpu heatsink

[dml]

@dml , this nessi firmware should be a good match for your huge cpu heatsink

That's awesome - thank you!

Hopefully I'll get the final bits very soon to start testing the machine properly.

[frank.lukas]

BTW, this looks an interesting project

http://www.alexandrugroza.ro/microelect ... index.html

If my other W32 card works, I might try building one of these using the current one as a donor board.

I have an ET4000W32i with 8x 256kx4 chips. Is it possible to solder 8x 1MBx4 chips in and add A9, creating so a 4MB W32i ISA card? The W32i GPU chip has a MAD9 pin.

[PhilC]

@frank.lukas the cards that I've seen that do 4mb all have 8 chips but I guess it's possible by adding the appropriate address line. You'd need to read the datasheet

[agranlund]

Updated rvbios to claim _MCH cookie value 0x00070000 for Raven instead of having it as -1
(V4SA is using 0x00060000 so I took the next free one as far as I'm aware)