Raspberry Pi / Mushashi powered 68k Hardware Emulator

IanP · 26 October 2020, 04:46

Claude Schwarz has posted on twitter that he has Diagrom running on an A500 with a Raspberry Pi and interface plugged into it where the 68000 should be.
https://twitter.com/Claude1079/statu...825558530?s=20

I don't know what sort of performance is possible with the CPU emulation on the Pi and the hardware interfacing. But there may be some interesting hybrid possibilities in addition to emulation (I'm thinking A314 on steroids).

Ernst Blofeld · 26 October 2020, 17:30

I'd love to know more about this, but I'm afraid I don't have the expertise to really understand it. The 7ish MHz that the 68K originally ran at is very slow by modern standards, but is it actually possible to interface something like a RaspberryPi to the 68K socket and actually make it work?

Niklas · 26 October 2020, 18:07

Quote:

Originally Posted by Ernst Blofeld

... but is it actually possible to interface something like a RaspberryPi to the 68K socket and actually make it work?

It is, he actually got it to run Pinball Dreams just today: https://twitter.com/Claude1079/statu...67372853190659

Sim085 · 26 October 2020, 18:54

Finally!

I have been dreaming about this since the first day the Raspberry Pi came out. Unfortunately I am no hardware guru (I am no hardware nothing actually) and therefore could never do anything about it. Finally projects like this are under development. Cannot wait for something similar also for the A1200.

Looking so forward for this.

Sim085 · 26 October 2020, 19:06

As I said I am no expert. However I believe for the Amiga changes nothing, signals are sent to the CPU and signals are returned from the CPU, the only difference is that the CPU is emulated by the raspberry pi. It is a great project. Wonder what pi resources can be shared.

Quote:

Originally Posted by Ernst Blofeld

I'd love to know more about this, but I'm afraid I don't have the expertise to really understand it. The 7ish MHz that the 68K originally ran at is very slow by modern standards, but is it actually possible to interface something like a RaspberryPi to the 68K socket and actually make it work?

IanP · 26 October 2020, 19:22

As I understand it he is using the GPIO connector in a mode called SMI (Secondary Memory Interface). This gives 18 data bits and 6 address bits and read/write signals. This talks to a MAX II CPLD on the interface card between the PI and the 68000 socket. The interface card also includes a set of latch ICs. So the PI can signal the CPLD probably using the SMI address lines and a combination of the read/write lines "the lower16 bits for the address latches are on the SMI databus", "the upper 8 bits for the address latches are on the SMI data bus", "8 or 16 bits to write to the databus latches are on the SMI databus" or "get the contents of the Amiga data bus into the latches", "put the contents of the data latches on the SMI databus". there are about 20 other signals (bus control, interupts etc.) on the 68000 that also need to be handled by the CPLD and PI.

Radertified · 26 October 2020, 23:39

According to the Musashi GitHub, it's a "68000, 68010, 68EC020, 68020, 68EC030, 68030, 68EC040 and 68040 emulator".

I've been waiting for FPGA as the next iteration of budget accelerators, but it may be Pi powered which is pretty exciting!

jotd · 26 October 2020, 23:50

Earlier this year, Musashi author allowed me to contribute to the emulator to fix 68040 features (missing/wrong instructions, FPU stuff), and I also suggested a few optimizations.

So if there are issues with Musashi itself I can help. Where Musashi is excellent is because of its architecture. It's rather quick to have something running with it.

(but of course Amiga custom chips aren't supported, but that probably doesn't matter here)

NovaCoder · 27 October 2020, 00:55

Yep this is very interesting, a cheap and fast accelerator would be great for the classics.

I've heard of a few of these hybrid cards being discussed over the years, I'd personally love to see an FPGA/ARM hybrid solution released as a plug in accelerator....that would be very cool.

khph_re · 27 October 2020, 10:21

Quote:

Originally Posted by NovaCoder

Yep this is very interesting, a cheap and fast accelerator would be great for the classics.

I've heard of a few of these hybrid cards being discussed over the years, I'd personally love to see an FPGA/ARM hybrid solution released as a plug in accelerator....that would be very cool.

Definitely, I've never watched any of the 060 demo's on real hardware, the gulf in cost between my 030 and an 060 has always been to great for me. I hope one of these devices can bridge that divide someday.

madgrizzle · 27 October 2020, 17:45

It seems even with some hacked together support for fastmem, it is already pretty quick.

https://twitter.com/Claude1079/statu...22503716081665

amiman99 · 27 October 2020, 19:02

This is what @majsta Vampire should have been, CPU and RAM, not plus everything else, or stand alone.
I hope something comes from it.

1NOM155 · 27 October 2020, 20:32

This could change a lot, its seems very promising project. congrats

rare_j · 27 October 2020, 23:22

Quote:

Originally Posted by Sim085

Cannot wait for something similar also for the A1200.

Would probably be more difficult as there's no cpu socket for the 680ec20. It'd have to go on via the trapdoor connector I think which is more complicated.

IanP · 27 October 2020, 23:57

Quote:

Originally Posted by amiman99

This is what @majsta Vampire should have been, CPU and RAM, not plus everything else, or stand alone.
I hope something comes from it.

The Raspberry PI could add everything the Vampire boards have and more if the software is written to make the features available from the emulator.

Bruce Abbott · 28 October 2020, 03:46

Quote:

Originally Posted by amiman99

This is what @majsta Vampire should have been, CPU and RAM, not plus everything else, or stand alone.
I hope something comes from it.

"Everything else" being extra RAM, RTG and IDE? I disagree. What's the point of a fast CPU without those other things?

This Raspberry Pi CPU emulator is interesting, and could be attractive if it is cheap. However I doubt that it could match the performance of the Vampire, and I feel happier with real hardware anyway.

Seems a pity to use a Pi without the Amiga having access to its video, RAM, SD Card etc. Oops! I forgot, we don't want 'everything else'.

amiman99 · 28 October 2020, 05:40

Quote:

Originally Posted by Bruce Abbott

"Everything else" being extra RAM, RTG and IDE? I disagree. What's the point of a fast CPU without those other things?

This Raspberry Pi CPU emulator is interesting, and could be attractive if it is cheap. However I doubt that it could match the performance of the Vampire, and I feel happier with real hardware anyway.

Seems a pity to use a Pi without the Amiga having access to its video, RAM, SD Card etc. Oops! I forgot, we don't want 'everything else'.

When you add more features, you add more cost, adds dev time, you know feature creep. Then at the end it costs €300-€450.
I'm not saying Vampire is bad.

Sim085 · 28 October 2020, 08:15

I always saw the advantage of putting a raspberry pi to emulate resources as a cheap alternative since the resources are there available to use on the raspberry pi and the raspberry pi is mass produced (unlike any amiga specific hardware).

I do not see why if the cpu and fast ram are emulated by the pi, why then storage cannot also be emulated by the pi. After all aren't those signals also going through the CPU socket? Maybe people with more knowledge then me can confirm or reject, I am really curious, I always thought so however given there are cards with ide.

I understand that the emulation software might not have reached that point (I do not know, maybe it already does). However the fun part is that this moves the problem to the software world rather then the hardware world + more powerful raspberry pi will continue to come out.

Quote:

Originally Posted by amiman99

When you add more features, you add more cost, adds dev time, you know feature creep. Then at the end it costs €300-€450.
I'm not saying Vampire is bad.

madgrizzle · 28 October 2020, 14:45

I agree scope creep drives price and delivery time up, but with him looking at moving to a CM4 with this, then the only Amiga-specific hardware is the carrier board. He could start with an initial version with just the functionality his adapter board currently has and down the road, if he desires, he could release a different version with hdmi, Ethernet, whatever. The CM4 would still remain the same. And if the CM5 comes out, people can just swap that in if he updates the software to support it. It provides a level of future-proofing that's not readily available with the current (and other future) accelerators out there. I have a 3640 with an '060 and am hesitant about some of the newer accelerator designs where you have to solder the '060 into them.

roondar · 28 October 2020, 15:09

That's quite cool!
Hope it ends up very successful, a PI based accelerator would be a very useful alternative for when the 680x0's start running out.

26 October 2020, 04:46	#1
IanP Registered User Join Date: Mar 2015 Location: Bristol/UK Posts: 166	Raspberry Pi / Mushashi powered 68k Hardware Emulator Claude Schwarz has posted on twitter that he has Diagrom running on an A500 with a Raspberry Pi and interface plugged into it where the 68000 should be. https://twitter.com/Claude1079/statu...825558530?s=20 I don't know what sort of performance is possible with the CPU emulation on the Pi and the hardware interfacing. But there may be some interesting hybrid possibilities in addition to emulation (I'm thinking A314 on steroids).

26 October 2020, 18:54	#4
Sim085 Registered User Join Date: Apr 2009 Location: N/A Posts: 962	Finally! I have been dreaming about this since the first day the Raspberry Pi came out. Unfortunately I am no hardware guru (I am no hardware nothing actually) and therefore could never do anything about it. Finally projects like this are under development. Cannot wait for something similar also for the A1200. Looking so forward for this. Last edited by Sim085; 26 October 2020 at 19:00.

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26 October 2020, 17:30	#2
Ernst Blofeld <optimized out> Join Date: Sep 2020 Location: <optimized out> Posts: 321	I'd love to know more about this, but I'm afraid I don't have the expertise to really understand it. The 7ish MHz that the 68K originally ran at is very slow by modern standards, but is it actually possible to interface something like a RaspberryPi to the 68K socket and actually make it work?

26 October 2020, 19:22	#6
IanP Registered User Join Date: Mar 2015 Location: Bristol/UK Posts: 166	As I understand it he is using the GPIO connector in a mode called SMI (Secondary Memory Interface). This gives 18 data bits and 6 address bits and read/write signals. This talks to a MAX II CPLD on the interface card between the PI and the 68000 socket. The interface card also includes a set of latch ICs. So the PI can signal the CPLD probably using the SMI address lines and a combination of the read/write lines "the lower16 bits for the address latches are on the SMI databus", "the upper 8 bits for the address latches are on the SMI data bus", "8 or 16 bits to write to the databus latches are on the SMI databus" or "get the contents of the Amiga data bus into the latches", "put the contents of the data latches on the SMI databus". there are about 20 other signals (bus control, interupts etc.) on the 68000 that also need to be handled by the CPLD and PI.

26 October 2020, 23:39	#7
Radertified Registered User Join Date: Jan 2011 Location: - Posts: 728	According to the Musashi GitHub, it's a "68000, 68010, 68EC020, 68020, 68EC030, 68030, 68EC040 and 68040 emulator". I've been waiting for FPGA as the next iteration of budget accelerators, but it may be Pi powered which is pretty exciting!

26 October 2020, 23:50	#8
jotd This cat is no more Join Date: Dec 2004 Location: FRANCE Age: 52 Posts: 8,160	Earlier this year, Musashi author allowed me to contribute to the emulator to fix 68040 features (missing/wrong instructions, FPU stuff), and I also suggested a few optimizations. So if there are issues with Musashi itself I can help. Where Musashi is excellent is because of its architecture. It's rather quick to have something running with it. (but of course Amiga custom chips aren't supported, but that probably doesn't matter here)

27 October 2020, 00:55	#9
NovaCoder Registered User Join Date: Sep 2007 Location: Melbourne/Australia Posts: 4,400	Yep this is very interesting, a cheap and fast accelerator would be great for the classics. I've heard of a few of these hybrid cards being discussed over the years, I'd personally love to see an FPGA/ARM hybrid solution released as a plug in accelerator....that would be very cool.

27 October 2020, 17:45	#11
madgrizzle Registered User Join Date: Oct 2020 Location: Tallahassee Posts: 2	It seems even with some hacked together support for fastmem, it is already pretty quick. https://twitter.com/Claude1079/statu...22503716081665

27 October 2020, 19:02	#12
amiman99 Registered User Join Date: Sep 2009 Location: San Antonio, TX USA Age: 50 Posts: 1,184	This is what @majsta Vampire should have been, CPU and RAM, not plus everything else, or stand alone. I hope something comes from it.

27 October 2020, 20:32	#13
1NOM155 Registered User Join Date: Apr 2015 Location: Lisbon Posts: 65	This could change a lot, its seems very promising project. congrats

28 October 2020, 14:45	#19
madgrizzle Registered User Join Date: Oct 2020 Location: Tallahassee Posts: 2	I agree scope creep drives price and delivery time up, but with him looking at moving to a CM4 with this, then the only Amiga-specific hardware is the carrier board. He could start with an initial version with just the functionality his adapter board currently has and down the road, if he desires, he could release a different version with hdmi, Ethernet, whatever. The CM4 would still remain the same. And if the CM5 comes out, people can just swap that in if he updates the software to support it. It provides a level of future-proofing that's not readily available with the current (and other future) accelerators out there. I have a 3640 with an '060 and am hesitant about some of the newer accelerator designs where you have to solder the '060 into them.

28 October 2020, 15:09	#20
roondar Registered User Join Date: Jul 2015 Location: The Netherlands Posts: 3,406	That's quite cool! Hope it ends up very successful, a PI based accelerator would be a very useful alternative for when the 680x0's start running out.

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