Suska 68000 core

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exxos
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Suska 68000 core

Post by exxos » Mon Nov 27, 2017 10:00 pm

I have been talking briefly to Ingo Uhlemann about the Suska core. We have been digging through the code as far as we can tell it is a cycle accurate 68000 core.. Which I was actually shocked about..

---- Description: ----
---- This model provides an opcode and bus timing compatible ip ----
---- core compared to Motorola's MC68000 microprocessor.



It also seems to be synchronising DTACK

---- Synchronous timing topics: ----
---- During the synchronous timing, the DTACKn must not be ----
---- asserted and due to asynchronous timing, the VPAn must not ----
---- be asserted, otherwise unpredictable behavior will result

P_WAITSTATES: process
-- During read, write or read modify write processes, the read access is delayed by wait
-- states (slow read, slow write) if there is no DTACKn asserted until the end of S4.
-- This is done by stopping the slice counter. After the halt, in principle a S5 would be
-- possible. This is not correct for not asserted DTACKn. This process provides a locking
-- of this forbidden case and the stop control for the slice counter. For more information
-- see the 68000 processor data sheet (bus cycles).


It also seems to have all the control lines etc in there also.. Such as BGACK, VMA, etc etc

We are considering building a development boards to investigate this... It looks like a complete core, and if we can tweak it to give faster internal instructions, then there is really no need continue trying to overclocked the original CPU as the core would do it anyway.

Here are the files in case I lose them...
vhdl.zip
(1.62 MiB) Downloaded 17 times
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
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Zarchos
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Re: Suska 68000 core

Post by Zarchos » Tue Dec 26, 2017 4:51 am

I have no idea if it is relevant or not, but the latest QL clone uses a 68000 FPGA giving the power of a 68000 running at 40 Mhz.
It has peculiar features like 1 cycle multiplication. (The FPGA has socalled "sysDSP" blocks for high performance multiply and accumulate).
No idea if that brings something useful here, but the author of this new ql (Q68) can be found on qlforum.co.uk and he is a nice and helpful person.

And yes, I have ordered 2 Q68s .... they will proudly sit next to my Falcon.

Petari
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Re: Suska 68000 core

Post by Petari » Tue Dec 26, 2017 7:41 am

Well, I'm sure that it is possible to make such 68000 compatible FPGA clone, so only CPU, with all lines as on original, what can be replacement CPU.

But ideal case would be to make it working in at least 3 modes:
1. 100% same speed as original - because old SW compatibility.
2. Internal faster, same bus speed as 8 MHz org. - that would be what exxos meant, I guess. So, can work with org. RAM, org peripherals, but faster. How much faster ? It depends a lot of SW running. In any case, speed gain will be not so big. I guess that average max some 80% .
3. Everything faster mode - then will need of course faster RAM in first place. Access to peripherals may remain at regular ST speed, or to be faster.

And latest mode just indicates that designers need to think not only about CPU self, but about whole computer design.
Those who did not think about it properly would be Vampire designers, in my opinion.

We need compatibility and we want speed. Those 2 go not together at once. But user can select what mode to run.
I think that it is great idea to push 68000 as much can, instead some 68020-80 - they are not 100% code compatible.

Zarchos
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Re: Suska 68000 core

Post by Zarchos » Tue Dec 26, 2017 8:48 am

I wonder what is left of the original hardware when a card like a Vampire is used.
Still, don't misunderstand me : I find it awesome for the amount of work and skills involved in such projects.

Petari
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Re: Suska 68000 core

Post by Petari » Tue Dec 26, 2017 8:57 am

Zarchos wrote:
Tue Dec 26, 2017 8:48 am
I wonder what is left of the original hardware when a card like a Vampire is used.
Still, don't misunderstand me : I find it awesome for the amount of work and skills involved in such projects.
I meant here design of CPU core self. As I know, there is nothing of ST org. HW implemented yet.
And CPU core in Vampire is not compatible. That's the problem.

Zarchos
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Re: Suska 68000 core

Post by Zarchos » Tue Dec 26, 2017 10:16 am

Can't the VHDL code for the Mist or Mister serve as a working base ?
Sorry I don't know enough about FPGA although I have started reading an introductory book about VHDL.

Cyprian
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Re: Suska 68000 core

Post by Cyprian » Tue Dec 26, 2017 11:13 am

exxos wrote:
Mon Nov 27, 2017 10:00 pm
We are considering building a development boards to investigate this... It looks like a complete core, and if we can tweak it to give faster internal instructions, then there is really no need continue trying to overclocked the original CPU as the core would do it anyway.
what about porting Suska core to existing hardware like MiST or MiSTer?

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Re: Suska 68000 core

Post by exxos » Tue Dec 26, 2017 11:21 am

I opened a new topic about CPU compatibility issues such, rather than post it here as it was drifting a lot off topic..

viewtopic.php?f=29&t=473
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.

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Re: Suska 68000 core

Post by exxos » Tue Dec 26, 2017 11:28 am

Cyprian wrote:
Tue Dec 26, 2017 11:13 am
exxos wrote:
Mon Nov 27, 2017 10:00 pm
We are considering building a development boards to investigate this... It looks like a complete core, and if we can tweak it to give faster internal instructions, then there is really no need continue trying to overclocked the original CPU as the core would do it anyway.
what about porting Suska core to existing hardware like MiST or MiSTer?
While I cannot say for that, as I know nothing about VHDL programming or the MiST.. You would have to speak to the developers of those machines about it.. But of course the whole system architecture is replaced on those machines, so cannot simply just test out the CPU which is what I was really talking about. It would not be a fair test otherwise.

I was just looking at the Suska core as it should be relatively simple port to get working.. Or at least test it out.. As for adding changes into the core, it is nothing I would be able to do, someone else would have to do it. But as support from other people is always basically near nothing, it would fall on my shoulders to learn all about it all and do the changes myself, this would just be too much work for me to take on. But of course if someone else took on the work I could integrate cause my future booster designs.

But of course a first step would be to validate how compatible the core was before making any decisions. But this really depends on support from others ultimately. If there is no help with the project, then I will likely just stick to real CPU's.
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.

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