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Free Core, Some Assembly Required

RISC-V rallies engineers for open hardware
1/7/2016 07:50 AM EST
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KarlS01
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Still another RISC ISA/ load store machine,,,Ho Hum!
KarlS01   1/12/2016 10:33:44 AM
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RISC came about because compilers had problems using CISC, but every RISC requires a new compiler.  On top of that, the RISC is running as/emilating a stack machine.

A compiler generates a compact intermediate language which is byte code that is EXPANDED to RISC code sometimes at run time JIT compiler which inserts the loads and stores.

Then the superscalar crowd tells us that the data is in register filess so the loads and stores do not access memory --  RISCV load and store certainly expect to access memory and will do so unless the CPU is designed as a super scalar.  Yes memory accesses may be reduced somewhat.

Systems have problems due to the "memory wall" so there certainly are a lot of memory accesses.

The compiler can essentially be eliminated by parsing the source code to extract the control flow and then a straight forward FSM can be designed to execute the control flow.

Another factor is that accxelerators and GPUs are given a block of data that is kept in local memory for peocessing,  ASMP is alive and well.

I have a prototype FPGA stack machine that uses three dual port memories and a couple of hundred LUTs to execute C source code.

rick merritt
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Re: slight correction on my coreboot talk
rick merritt   1/10/2016 7:55:31 PM
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@ronaldgminnich I rewrote the sentence on Coreboot to make these points more clear. Sorry for any confusion and stay in touch!

krste
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Re: RISC-V core in 350 LUTS!
krste   1/10/2016 1:43:40 PM
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Slides from the 3rd workshop are now available at the riscv.org website.

Videos to follow.

ronaldgminnich
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slight correction on my coreboot talk
ronaldgminnich   1/10/2016 1:31:53 PM
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Hi, I enjoyed the article, but I do have a slight correction.

Coreboot runs on all Chromebook and Chromebox devices. There no Android devices that I know of running coreboot.

Coreboot runs on the RISCV simulators and has for 15 months, booting to Linux. We are hoping to have it on RV64G hardware as soon as we can get some :-)

There are no available RISCV Chromebook/box devices and I am sorry if I left that impression.

Thanks!

ron

krste
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Re: RISC-V core in 350 LUTS!
krste   1/8/2016 7:29:12 PM
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Yes, both slides (soon) and video (later) as before.

 

modal
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Re: RISC-V core in 350 LUTS!
modal   1/8/2016 2:55:19 PM
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Are the videos going to be placed online again?

http://riscv.org/workshop-jun2015.html

http://riscv.org/workshop-jan2015.html


Didn't see the second seminar till just now.

krste
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RISC-V is not a free core, it's a free and open ISA
krste   1/8/2016 4:56:36 AM
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Hi Rick,

Thanks for great coverage of the event.

I just wanted to clarify for your readers that RISC-V is not an open-source core - it's a free and open ISA specification around which a whole ecosystem is being built.

Of course, there are now many open-source RISC-V cores available, and not just from Berkeley.

But there are also quite a few proprietary RISC-V cores in various stages of development, most of which will probably never be publicly announced.

 

rick merritt
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Re: India Processor Effort
rick merritt   1/8/2016 12:55:00 AM
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@GSMD: Thanks for the url. Let's talk.

pattrsn
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RISC-V core in 350 LUTS!
pattrsn   1/7/2016 2:03:29 PM
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While there were many impressive presentations, the highlight for me was Jan Gray's "GRVI-Phalanx" that fit ~400 RISC-V cores onto a single FPGA.

Each runs at >300 MHz and needs only 350 LUTS. Stated alternatively, he is able to deliver 1 million instructions per second per LUT, which must be a new world record. Note even less ambitious processor cores take ~2000 LUTS and run at ~100-150 MHz.

This achievement is a testament to both the Gray's engineering poweress and the simple elegance of RISC-V.

perl_geek
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Siblings, not derivatives
perl_geek   1/7/2016 1:58:45 PM
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I'm not sure who would be more offended by your description of FreeBSD as a "Linux variant"; the BSD people or the Linux people.

Though both descend from and embody The One True Religion (Unix), they are entirely separate bodies of code, with different histories and licenses. Enlightenment has many paths. :-)*

 

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