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Groups > comp.arch.embedded > #29463

Re: Custom CPU Designs

Newsgroups comp.arch.embedded
Date 2020-04-16 12:28 -0700
References <abb9b585-5a14-45d0-b617-543a009a176c@googlegroups.com> <xrB*I6GPx@news.chiark.greenend.org.uk> <cff27757-6124-4094-a015-f85a83fe93b8@googlegroups.com>
Message-ID <d1aea0fb-d970-4ddd-aac2-dcabaf3d672f@googlegroups.com> (permalink)
Subject Re: Custom CPU Designs
From jim.brakefield@ieee.org

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On Thursday, April 16, 2020 at 9:40:55 AM UTC-5, Rick C wrote:
> On Thursday, April 16, 2020 at 6:59:29 AM UTC-4, Theo wrote:
> > Rick C <gnuarm.deletethisbit@gmail.com> wrote:
> > > In the Forth language group there are occasional discussions of custom
> > > processors.  This is mostly because a simple stack processor can be
> > > designed to be implemented in an FPGA very easily, taking little resources
> > > and running at a good speed.  Such a stack processor is a good target for
> > > Forth.
> > > 
> > > I know there are many other types of CPU designs which are implemented in
> > > FPGAs.  I'm wondering how often these are used by the typical embedded
> > > developer?
> > 
> > It's not uncommon when you have an FPGA doing some task to need a processor
> > in there to manage it - for example to handle error conditions or to report
> > status over some software-friendly interface like I2C, or classical printf
> > debugging on a UART.
> > 
> > Xilinx provides Microblaze and Intel/Altera provide NIOS, which are a bit
> > legacy (toolchains aren't that great, etc), although designed to be fairly
> > small.  There's increasing interest in small 32-bit RISC-V cores for this
> > niche, since the toolchain is improving and the licensing conditions more
> > liberal (RISC-V itself doesn't design cores, but lots of others - including
> > ourselves - have made open source cores to the RISC-V specification).
> 
> Someone showed me that RISC-V can be a small solution, but at that size it isn't fast.  So the size performance tradeoff isn't so great.  Stack processors tend to be very lean and speed effective without pipelining.  I know my processor was designed to run 1 instruction per clock cycle on all instructions.  
> 
> 
> > I don't see that Forth has much to speak to this niche, given these cores
> > are largely offloading work that's fiddly to do in hardware and people just
> > want to write some (usually) C to mop up the loose ends.  I can't see what
> > Forth would gain them for this.
> 
> Not sure what you mean about Forth and "speaking".  Forth is a natural language for a stack based processor.  Often there is a 1 to 1 mapping of instructions to language words.  It is also very easy to retarget to new modifications to a processor design. 
> 
> 
> > If you're talking using these processors as a compute overlay for FPGAs, a
> > different thing entirely, I'd suggest that a stack processor is likely not
> > very efficient in terms of throughput.  Although I don't have a cite to back
> > that up.
> 
> I recall someone had a very large compendium of soft core processors with size and speed measurements with a calculation of something like IPS/LUT.  It was amazing what some designs could achieve.  I wish I knew where to find that now. 
> 
> -- 
> 
>   Rick C.
> 
>   + Get 1,000 miles of free Supercharging
>   + Tesla referral code - https://ts.la/richard11209

|>very large compendium of soft core processors
https://opencores.org/projects/up_core_list/summary

Several legacy processors are listed:
https://opencores.org/projects/up_core_list/downloads
uP_core_list_by_style-clone190221.pdf

Also look into MISTer as it supports several legacy systems.
None are competitive speed wise with high performance uP.

With LUTs costing less than $0.001 each some soft core uPs are inexpensive, free if you have unused LUTs and block RAMs.
For debug, changing block RAM contents is much faster than rerunning the FPGA design.

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Thread

Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-15 20:51 -0700
  Re: Custom CPU Designs Theo <theom+news@chiark.greenend.org.uk> - 2020-04-16 11:59 +0100
    Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-16 13:28 +0200
    Re: Custom CPU Designs Grant Edwards <invalid@invalid.invalid> - 2020-04-16 13:10 +0000
      Re: Custom CPU Designs Theo <theom+news@chiark.greenend.org.uk> - 2020-04-16 22:16 +0100
        Re: Custom CPU Designs Grant Edwards <invalid@invalid.invalid> - 2020-04-16 22:01 +0000
          Re: Custom CPU Designs Paul Rubin <no.email@nospam.invalid> - 2020-04-16 17:13 -0700
            Re: Custom CPU Designs jim.brakefield@ieee.org - 2020-04-16 18:10 -0700
            Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-16 18:37 -0700
              Re: Custom CPU Designs Paul Rubin <no.email@nospam.invalid> - 2020-04-16 22:08 -0700
              Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-17 10:02 +0200
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-17 10:49 +0100
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-17 15:44 +0200
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-17 15:23 +0100
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-17 18:15 +0200
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-17 17:49 +0100
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-18 15:06 +0200
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-18 16:08 +0100
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-20 15:13 +0200
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-20 14:24 +0100
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-20 16:00 +0200
                Re: Custom CPU Designs Paul Rubin <no.email@nospam.invalid> - 2020-04-20 14:32 -0700
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-20 23:55 +0100
                Re: Custom CPU Designs Reinhardt Behm <rbehm@hushmail.com> - 2020-04-21 15:14 +0800
                Re: Custom CPU Designs Theo <theom+news@chiark.greenend.org.uk> - 2020-04-18 16:51 +0100
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-18 18:06 +0100
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-18 14:53 -0700
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-19 10:11 +0100
                Re: Custom CPU Designs upsidedown@downunder.com - 2020-04-19 13:19 +0300
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-19 11:33 +0100
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-20 15:26 +0200
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-20 14:59 +0100
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-19 13:37 -0700
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-19 22:02 +0100
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-19 22:15 +0100
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-19 15:02 -0700
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-20 02:03 +0100
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-18 14:44 -0700
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-20 15:20 +0200
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-20 14:57 +0100
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-18 12:38 -0700
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-20 15:58 +0200
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-20 16:27 +0100
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-20 17:36 -0700
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-21 14:02 +0200
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-21 06:15 -0700
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-21 17:25 +0200
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-21 16:56 +0100
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-21 12:42 -0700
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-21 23:16 +0100
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-22 11:10 +0200
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-22 08:09 -0700
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-22 20:07 +0200
                Re: Custom CPU Designs Paul Rubin <no.email@nospam.invalid> - 2020-04-18 13:09 -0700
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-18 21:28 +0100
                Re: Custom CPU Designs upsidedown@downunder.com - 2020-04-21 20:29 +0300
                Re: Custom CPU Designs Grant Edwards <invalid@invalid.invalid> - 2020-04-21 18:10 +0000
                Re: Custom CPU Designs upsidedown@downunder.com - 2020-04-22 09:54 +0300
                Re: Custom CPU Designs Grant Edwards <invalid@invalid.invalid> - 2020-04-22 13:19 +0000
                Re: Custom CPU Designs upsidedown@downunder.com - 2020-04-22 18:09 +0300
                Re: Custom CPU Designs Grant Edwards <invalid@invalid.invalid> - 2020-04-22 17:03 +0000
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-22 11:16 +0200
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-17 10:48 -0700
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-18 16:57 +0200
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-18 14:21 -0700
                Re: Custom CPU Designs Paul Rubin <no.email@nospam.invalid> - 2020-04-18 14:50 -0700
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-20 16:32 +0200
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-20 18:12 -0700
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-21 10:09 +0100
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-20 16:31 +0100
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-20 16:42 +0100
                Re: Custom CPU Designs upsidedown@downunder.com - 2020-04-18 00:43 +0300
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-18 17:07 +0200
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-17 09:11 -0700
                Re: Custom CPU Designs Paul Rubin <no.email@nospam.invalid> - 2020-04-17 12:17 -0700
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-17 13:22 -0700
                Re: Custom CPU Designs Paul Rubin <no.email@nospam.invalid> - 2020-04-17 14:48 -0700
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-17 15:27 -0700
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-20 16:53 +0200
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-20 17:03 +0100
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-20 19:39 +0200
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-20 21:25 +0100
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-20 18:27 -0700
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-21 17:58 +0200
                Re: Custom CPU Designs Niklas Holsti <niklas.holsti@tidorum.invalid> - 2020-04-21 19:41 +0300
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-21 14:01 -0700
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-21 23:21 +0100
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-19 20:53 +0200
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-19 14:47 -0700
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-20 02:11 +0100
                Re: Custom CPU Designs Paul Rubin <no.email@nospam.invalid> - 2020-04-19 18:31 -0700
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-19 20:32 -0700
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-20 07:46 +0100
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-20 00:33 -0700
                Re: Custom CPU Designs Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-04-20 11:01 +0100
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-20 17:44 +0200
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-20 19:57 -0700
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-21 18:02 +0200
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-21 14:56 -0700
            Re: Custom CPU Designs Theo <theom+news@chiark.greenend.org.uk> - 2020-04-17 16:34 +0100
              Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-20 17:57 +0200
                Re: Custom CPU Designs Theo <theom+news@chiark.greenend.org.uk> - 2020-04-21 15:20 +0100
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-21 08:26 -0700
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-21 18:09 +0200
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-21 15:00 -0700
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-22 11:28 +0200
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-22 08:24 -0700
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-22 20:18 +0200
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-22 11:45 -0700
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-23 17:47 +0200
                Re: Custom CPU Designs jim.brakefield@ieee.org - 2020-04-21 15:35 -0700
            Re: Custom CPU Designs Przemek Klosowski <przemek@tux.dot.org> - 2020-04-19 18:52 +0000
              Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-19 13:42 -0700
              Re: Custom CPU Designs Clifford Heath <no.spam@please.net> - 2020-04-20 22:59 +1000
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-20 17:01 -0700
                Re: Custom CPU Designs Clifford Heath <no.spam@please.net> - 2020-04-21 10:23 +1000
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-21 03:47 -0700
                Re: Custom CPU Designs Clifford Heath <no.spam@please.net> - 2020-04-22 09:26 +1000
                Re: Custom CPU Designs Theo <theom+news@chiark.greenend.org.uk> - 2020-04-22 22:06 +0100
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-22 14:18 -0700
                Re: Custom CPU Designs Theo <theom+news@chiark.greenend.org.uk> - 2020-04-23 22:35 +0100
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-21 18:20 +0200
                Re: Custom CPU Designs Dimiter_Popoff <dp@tgi-sci.com> - 2020-04-22 18:16 +0300
                Re: Custom CPU Designs Grant Edwards <invalid@invalid.invalid> - 2020-04-22 17:06 +0000
                Re: Custom CPU Designs Dimiter_Popoff <dp@tgi-sci.com> - 2020-04-22 20:17 +0300
                Re: Custom CPU Designs Grant Edwards <invalid@invalid.invalid> - 2020-04-22 17:28 +0000
                Re: Custom CPU Designs George Neuner <gneuner2@comcast.net> - 2020-04-23 04:59 -0400
                Re: Custom CPU Designs jim.brakefield@ieee.org - 2020-04-20 17:27 -0700
              Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-20 17:58 +0200
                Re: Custom CPU Designs pault.eg@googlemail.com - 2020-04-21 01:00 -0700
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-21 19:21 +0200
          Re: Custom CPU Designs Theo <theom+news@chiark.greenend.org.uk> - 2020-04-17 17:18 +0100
    Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-16 07:40 -0700
      Re: Custom CPU Designs jim.brakefield@ieee.org - 2020-04-16 12:28 -0700
        Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-16 13:50 -0700
          Re: Custom CPU Designs jim.brakefield@ieee.org - 2020-04-16 14:19 -0700
          Re: Custom CPU Designs Theo <theom+news@chiark.greenend.org.uk> - 2020-04-16 22:33 +0100
    Re: Custom CPU Designs Clifford Heath <no.spam@please.net> - 2020-04-17 11:29 +1000
      Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-16 18:42 -0700
        Re: Custom CPU Designs Clifford Heath <no.spam@please.net> - 2020-04-17 12:35 +1000
          Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-16 20:01 -0700
            Re: Custom CPU Designs Clifford Heath <no.spam@please.net> - 2020-04-17 14:54 +1000
              Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-16 23:54 -0700
              Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-17 10:38 +0200
                Re: Custom CPU Designs Rick C <gnuarm.deletethisbit@gmail.com> - 2020-04-17 09:13 -0700
                Re: Custom CPU Designs David Brown <david.brown@hesbynett.no> - 2020-04-20 18:02 +0200

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