Really crazy idea ...

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SolderGirl
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Really crazy idea ...

Post by SolderGirl » Fri Aug 10, 2018 5:26 pm

Recently i watched a talk from CCC, a congress held yearly by a german hacker group.
One talk was about hacking the PS4, wich is totally useless to us as "Atarians".

But there is one little piece of information in this talk wich made me curious.
They hacked the thing by basically routing a PCI Express connection over a 115200 bps serial line, and then hacking into that.
Obviously, while PCIe is designed to be very fast, it is also very tolerant to delays and slowdowns.

So maybe, just maybe, it would be possible to somehow connect a PCIe Graphics Card to the Atari, maybe over the DMA-Port?
The serial ports of the ST only do 19200bps, that would be too slow for use, but the DMA-Port can do well over 1 MB/s,
that might be enough to run a framebuffer at relatively low resolution.

If someone wants to look into what they did, it's after about 6 minutes in this Video:


PS: Wouldn't it be suuuuuuper awesome to say "Look, my Atari ST has a GTX1080Ti in it!"

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Re: Really crazy idea ...

Post by exxos » Fri Aug 10, 2018 5:37 pm

You can hack things right onto the 68000 bus, no need to do much else. ET4000 graphics card is basically just that. Of course need drivers to work.

Could have a x86 quad core CPU onto the bus while at it, not like any support for that, but be super fast for something ;)

Of course things easier if 16bit IO, or 32bit if using 020 or higher CPU.

EDIT:

Clones like the Milan had ISA/PCI slots much like a PC motherboard.

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SolderGirl
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Re: Really crazy idea ...

Post by SolderGirl » Fri Aug 10, 2018 5:51 pm

I had the idea not because of speed.
But those ET4000 cards are getting really hard to find these days,
and even if you find one, it still has "only" VGA output.

But PCIe cards are easy and cheap to find, and even the old and crappy ones
have DVI and often HDMI or DisplayPort outputs.

I don't even think about using much of the GPU at all, just a simple
Framebuffer like with the ET4k cards. Sure, it would run even faster when
it is directly on the 68k Bus, but that needs work to be done for bus logic.

What i basically dream about is something like the VoFa Adapter, just not
with ISA, but with PCIe Slot.

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Re: Really crazy idea ...

Post by exxos » Fri Aug 10, 2018 5:56 pm

Have you seen this project ?

viewtopic.php?f=29&t=330

Replacement shifter in FPGA, HDMI output.. of course when we get faster RAM access, no reason that core can't be updated with more colours higher resolutions.. and it won't need any special hardware or drivers either as its a "updated "shifter.

Also faster RAM means blitter can run at much higher speeds for more graphics processing power.. So isn't much need to go down route of other cards (though I do see the idea :) )
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

SolderGirl
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Re: Really crazy idea ...

Post by SolderGirl » Fri Aug 10, 2018 6:05 pm

Ok, i did not realize that.

Of course, UberShifter would be much more compatible and extremely awesome.

Still, it would be simply hillarious to run something like a RX580 in an Atari at 320x200 mode,
just for the lolz ;-)

PS: keep working on that Shifter, it sounds really amazing!

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Re: Really crazy idea ...

Post by Petari » Fri Aug 10, 2018 8:17 pm

DMA port can actually 2 MB sec, and that would be more than enough to transfer changes on screen to graphic card. But DMA port is not really good for it, because it is designed for so called block devices - hard disks in first place, where transfer goes in 512 byte and it's multiple long blocks (what is size of 1 sector). And that's not good for graphics - because you may need to write 222 bytes, so what with remaining 290 bytes ? They will spoil part of screen.
Interfacing will be problem too, need to add some complex logic for DMA transfers. Then, some higher res. and more colors are just too demanding for slow ST. CPU just will be too slow to process all data necessary.
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Re: Really crazy idea ...

Post by stephen_usher » Fri Aug 10, 2018 10:06 pm

What might be useful would be a VME/68000 bus to PCI adapter.

PCI graphics cards are far easier to come by than ISA ones, especially Mach64 based ones. You'd need a bus controller for the PCI bus and some sort of dual ported RAM probably, especially for any bus mastered AGP-GART emulation. The bonus would be that you'd isolate the two buses and the PCI could run at its proper 33MHz.

AGP would be too painful to do, especially with the strange high density edge connector.

You'd probably have to stick to 5V PCI, rather than 3.3V.

Whatever, it'd probably be a mammoth task.
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Re: Really crazy idea ...

Post by Cyprian » Fri Aug 10, 2018 10:07 pm

Petari wrote:
Fri Aug 10, 2018 8:17 pm
DMA port can actually 2 MB sec, and that would be more than enough to transfer changes on screen to graphic card. But DMA port is not really good for it, because it is designed for so called block devices - hard disks in first place, where transfer goes in 512 byte and it's multiple long blocks (what is size of 1 sector). And that's not good for graphics - because you may need to write 222 bytes, so what with remaining 290 bytes ? They will spoil part of screen.
Interfacing will be problem too, need to add some complex logic for DMA transfers. Then, some higher res. and more colors are just too demanding for slow ST. CPU just will be too slow to process all data necessary.
IIRC minimal data block in ST DMA is 16 bytes.
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Re: Really crazy idea ...

Post by SolderGirl » Fri Aug 10, 2018 10:56 pm

Cyprian wrote:
Fri Aug 10, 2018 10:07 pm
Petari wrote:
Fri Aug 10, 2018 8:17 pm
DMA port can actually 2 MB sec, and that would be more than enough to transfer changes on screen to graphic card. But DMA port is not really good for it, because it is designed for so called block devices - hard disks in first place, where transfer goes in 512 byte and it's multiple long blocks (what is size of 1 sector). And that's not good for graphics - because you may need to write 222 bytes, so what with remaining 290 bytes ? They will spoil part of screen.
Interfacing will be problem too, need to add some complex logic for DMA transfers. Then, some higher res. and more colors are just too demanding for slow ST. CPU just will be too slow to process all data necessary.
IIRC minimal data block in ST DMA is 16 bytes.
If that is correct, it would be perfect.
Because PCIe works with a packet protocol, with packets of 4 x 32bit words each. So That is exactly 16 bytes packets. That would fit nicely.
PS:
"The frame format for PCIe is shown in the graphic below. The frame is made up of a 1-byte Start-of-Frame, 2-byte Sequence Number, 16 or 20-byte Header, 0 to 4096-byte Data field, 0 to 4-byte ECRC field, 4-byte LCRC, and 1-byte End-of Frame. The smaller the number of bits transferred in the data field the greater the over-head becomes. A zero byte data field results in a 100 percent over-head, because no data was transferred."

From this, it looks like a typical Frame would be something like 28 bytes + Data, but i don't know the data formats used.
Also i don't know how flexible the block sizes for the DMA port are

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Re: Really crazy idea ...

Post by Cyprian » Fri Aug 10, 2018 11:10 pm

I found that.
DMA has two FIFO buffers - Read and Write, each 8 words long.
"The FIFOs are not flushed automatically at the end of a transfer, and therefore it is only possible to transfer data in multiples of 16 bytes"
http://info-coach.fr/atari/documents/_m ... amming.pdf
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