RetroBrew Computers Forum: General Discussion

Home » RBC Forums » General Discussion » Retro-uC (An open silicon microcontroller with a Z80, MOS6502, and M68K)

Show: Today's Messages :: Show Polls :: Message Navigator

Retro-uC [message #3633]

Sat, 21 October 2017 13:44

w9gb
Messages: 55
Registered: October 2015
Location: Chicago, IL

Member

Retro-uC
An open silicon microcontroller with a Z80, MOS6502, and M68K - start the open silicon revolution.
https://www.crowdsupply.com/chips4makers/retro-uc

The Retro-uC pilot run will produce an open source silicon ASIC that contains the RTL for some retro CPUs - the Zilog Z80, MOS 6502 and Motorola M68K. The IC will be on a board that has Arduino-compatible I/O for use in all your cool projects. But beyond the product itself, the intent is to put together an open source EDA flow and manufacturing supply chain that will make creating open silicon an easier process for any who care to get involved.

Report message to a moderator

Re: Retro-uC [message #3634 is a reply to message #3633]

Sat, 21 October 2017 15:33

etchedpixels
Messages: 333
Registered: October 2015

Senior Member

What has it got to offer over an existing FPGA board that can already run a dozen more processors, all sorts of different I/O configurations and all happily at the speed of the original processors. socz80 runs at 128MHz (to the point it needs caches to front the modern DRAM on the board) on an FPGA card.

I don't get why you need an ASIC when you can hit way over the original clock rates with synthesized processors even into the 32bit space. And once you push the clock rates up then you can't use the original I/O devices with the system except with a ton of wait states, or often modern ones because of the signal frequencies. At least if it's in an FPGA you can syntheize a 50MHz 8255 to go with your overfast processor.

The Arduino format with FPGA already exists - Papilo Duo for one does this. There's even a a shield for retro computing (vga, audio jacks, ps/2, atari joystick. microsd, control buttons, rs232).

Report message to a moderator

Re: Retro-uC [message #3635 is a reply to message #3634]

Sat, 21 October 2017 16:43

Andrew B
Messages: 467
Registered: October 2015
Location: Near Redmond, WA

Senior Member
Administrator

I think the part their stated goal to make custom ASIC fabrication easier is an admirable goal.

But I agree with that etchedpixels that it's not clear what this offers over say, Grant's Multicomp. The limited I/O pins of the Arduino formfactor will make it difficult to integrate into larger retro projects, while cheap and plentiful FPGA modules on eBay have tons of pins broken out for different uses.

Report message to a moderator

Re: Retro-uC [message #3637 is a reply to message #3634]

Sun, 22 October 2017 03:59

biged
Messages: 9
Registered: April 2016

Junior Member

I think an affordable open-source ASIC provider is an interesting idea: the headline is chips for $100 at quantity 100, and of course lower prices at larger volumes. There are a few retro computing projects which get to volumes of 100 and more, and there are a few projects priced at the $200 level, so the idea might have some good fit. It's hard to say what all the possibilities are until the idea is out there and people can try to apply it.

It's certainly easy to spend $200 on an FPGA dev board - although it's also possible to spend $50 or less. But dev boards are not so end-user friendly. If you compare the messages on say Stardot with the messages on the BBC Micro Facebook group, you see that there's a much larger audience of less-technical people who like a plug-and-play solution.

The thing to do, probably, is to look at the ways in which FPGAs don't work well, or are not acceptable to the target audience. Some proportion of retronauts would draw a distinction - rightly or wrongly - between a custom chip and an FPGA.

Report message to a moderator

Re: Retro-uC [message #3641 is a reply to message #3637]

Mon, 23 October 2017 15:36

etchedpixels
Messages: 333
Registered: October 2015

Senior Member

The custom ASICs at low volumes may well be interesting I don't disagree

In terms of FPGA I don't think FPGA or ASIC changes anything about plug and play. Theere are lots of FPGA plug and play boards, many of them ones where the user probably has no idea that it's done that way. At least one of the C64 65C816 super extenders for example doesn't actually have a 65C816. It and almost all the glue are an FPGA. The Vampire Amiga accelerators are another example I can think of. In fact they've now gone beyond emulating a 68K series processor to building their own soft "68080" Cool

Report message to a moderator

Re: Retro-uC [message #3642 is a reply to message #3641]

Mon, 23 October 2017 15:55

w9gb
Messages: 55
Registered: October 2015
Location: Chicago, IL

Member

.... like Jeff Leighton's KimKlone (KK) Project?
Short Summary
http://laughtonelectronics.com/Arcana/KimKlone/Kimklone_shor t_summary.html
Project
http://laughtonelectronics.com/Arcana/KimKlone/Kimklone_intr o.html

[Updated on: Mon, 23 October 2017 16:00]

Report message to a moderator

Re: Retro-uC [message #3643 is a reply to message #3642]

Mon, 23 October 2017 23:18

biged
Messages: 9
Registered: April 2016

Junior Member

Jeff Laughton's project is an excellent example of extending the 6502, but the design pre-dates FPGAs entirely - it's all built in discrete TTL.

Very interesting to hear there's an '816 design in FPGA - I don't know of any open source core. I would think high-volume obvious-spec offerings like packaged Amiga-in-a-joystick could get a lot of cost benefit from custom silicon. (But you do miss out on ability to fix problems or to upgrade in the field, even without special equipment, something which I believe Spectrum Next offers. That could be worth a lot, given the negative publicity of shipping a flawed early version. Perhaps early versions should be FPGA and a cost-reduced version use custom silicon. Wink

Report message to a moderator

Re: Retro-uC [message #3644 is a reply to message #3643]

Tue, 24 October 2017 03:52

biged
Messages: 9
Registered: April 2016

Junior Member

w9gb

.... like Jeff Leighton's KimKlone (KK) Project?

biged wrote on Mon, 23 October 2017 23:18

Jeff Laughton's project is an excellent example of extending the 6502, but the design pre-dates FPGAs entirely - it's all built in discrete TTL.

Oops, I see I've misunderstood - you're saying that KK in a custom chip would be rather interesting.

[Updated on: Tue, 24 October 2017 03:53]

Report message to a moderator

Re: Retro-uC [message #3645 is a reply to message #3644]

Tue, 24 October 2017 05:30

etchedpixels
Messages: 333
Registered: October 2015

Senior Member

@biged: There is a reason ASIC's require enormous amounts of simulation and validation Cool

Even a moderarely complex ASIC design however usually contains enough extra logic to switch between multiple paths and to disable certain features or optimizations, because you need a plan both for "I just spent a lot of money and it's got a bug" and also field discovered problems. Entertainingly in a lot of the silicon world the controls for these are known as 'chicken bits'.

Report message to a moderator

Re: Retro-uC [message #3646 is a reply to message #3645]

Tue, 24 October 2017 05:39

biged
Messages: 9
Registered: April 2016

Junior Member

Wow, a long time since I heard that term! Indeed, this might be the big negative for ASICs in the retro space - not only does it mean you need the volume to pay for the extra effort, but you need the practices, the skills, the discipline to make that effort count.

Report message to a moderator

Re: Retro-uC [message #3648 is a reply to message #3646]

Tue, 24 October 2017 07:48

Andrew B
Messages: 467
Registered: October 2015
Location: Near Redmond, WA

Senior Member
Administrator

There is a lot of good commentary on the Parallax Propeller 2 forum about the process of getting a custom ASIC made. Parallax is a pretty small company, the entire Propeller 2 design is being done by one person + community feedback, and they have prior experience from Propeller 1.

Report message to a moderator

Re: Retro-uC [message #3658 is a reply to message #3648]

Wed, 25 October 2017 07:35

biged
Messages: 9
Registered: April 2016

Junior Member

Thanks Andrew - I've seen those forums a couple of times, but I'm not a regular there. A possible starting point post:
http://forums.parallax.com/discussion/167433/prop2-costs

Report message to a moderator

Re: Retro-uC [message #3692 is a reply to message #3633]

Sun, 29 October 2017 11:14

Andrew B
Messages: 467
Registered: October 2015
Location: Near Redmond, WA

Senior Member
Administrator

I am super happy about the Propeller 2. The Propeller 1 has been an excellent companion chip for several RBC designs. Since Chip Gracy does the entire design himself (with help from the community on the Prop 2), they tend to be elegant designs that you can really wrap your mind around how the chip works.

Report message to a moderator

Re: Retro-uC [message #3935 is a reply to message #3643]

Tue, 12 December 2017 17:29

etchedpixels
Messages: 333
Registered: October 2015

Senior Member

biged wrote on Mon, 23 October 2017 23:18

Jeff Laughton's project is an excellent example of extending the 6502, but the design pre-dates FPGAs entirely - it's all built in discrete TTL.

Very interesting to hear there's an '816 design in FPGA - I don't know of any open source core

Its not open source. The 65C816 core they use is apparently supplied by WDC themselves.

Alan

Report message to a moderator

Previous Topic:	SD card socket for the Cyclone II v1.10 [solved]
Next Topic:	SBC V2 unstable (memory)

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Thu May 02 04:15:43 PDT 2024

Total time taken to generate the page: 0.00900 seconds