[lowrisc-dev] Getting Focused: Quick Release

Logan Streondj streondj at gmail.com
Fri Feb 20 20:02:49 GMT 2015

On Tue, Feb 17, 2015 at 08:54:31AM +0000, Alex Bradbury wrote:
> We went through a selection process when choosing our ISA and
> ultimately RISC-V won out. 

Okay, after having reviewed RISC-V some more, I agree with your
decision to go with it. The fact that there are already at least some
chips using it is a major boost.

> We're very aware of the challenges and the timelines involved in
> producing silicon. e.g. we have a 128-core research test chip on a
> 40nm process taping out this summer.
yes well as you mentioned it is somewhat unrelated. 
Though you mentioned that they have limited instruction sets.
I'm personally a fan of MISC architectures bundled with FPGA's.

> I'm not sure why you think we're
> anywhere near running out of steam, on the contrary we're just getting
> started.
> Alex

It's important to have a good start. 
For instance due to lack of GPU or even USB in OpenCores.
It may be best to go with a microcontroller.

Can make something that will fit an Arduino.
In addition to the RISC-V ISA, it will require
UART, EEPROM, Flash, SDRAM, A/D decoder,
so it could be a drop in replacement,
albeit with different ISA.

I'm here mostly to advocate for AGI friendly chips. 
a Libre FPGA with fully open toolchain being a main point.
EEPROM, Flash and SDRAM all work in that direction.

Also the boards are done, there are lots of -duino boards.
So if something comparable to the ATMega328 is made,
there is already a large market of potential buyers.

That way, all you have to focus on is the one chip.
It does have the constraints of voltage, size and function,
but it also means all those things don't have to be decided.

In terms of nm's I'd recommend using the largest width that gives the
desired functionality (a little more than ATMega328). 
wider width will lower the cost while also increase 
the half-life of the chips. 


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