[HN Gopher] 16-bit RISC-V processor made with carbon nanotubes (...
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       16-bit RISC-V processor made with carbon nanotubes (2019)
        
       Author : signa11
       Score  : 50 points
       Date   : 2022-06-15 03:01 UTC (2 days ago)
        
 (HTM) web link (arstechnica.com)
 (TXT) w3m dump (arstechnica.com)
        
       | messe wrote:
       | (2019)
       | 
       | IMO it's also debatable whether or not it should be really called
       | RISC-V, because RISC-V doesn't have a 16-bit ISA. Instead this
       | seems to use the same ISA, but it limits both data and addresses
       | to 16-bits (while keeping 32-bit instructions).
        
         | progre wrote:
         | Also, saying it's made with nanotubes kind of implies that
         | nanotubes was used as transistors. Instead, "nanotubes" seems
         | to be used as a substrate, and the transistors are formed using
         | traditional oxide doping.
        
         | yjftsjthsd-h wrote:
         | Thanks, that was my immediate question on reading the title - I
         | didn't think RISC-V had a 16-bit variant.
        
           | snvzz wrote:
           | It doesn't.
           | 
           | It is possible to e.g. have 32bit registers but 16bit ALU
           | (and do 32bit operations in steps, hidden from the
           | programmer).
           | 
           | This is how the 68000 worked.
        
             | jecel wrote:
             | And the Z80 had a 4 bit ALU. Note that the 68000 actually
             | had three 16 bit ALUs and could crunch 48 bits per cycle,
             | depending on what operations you were doing since one was a
             | full ALU while the other two more simple
             | adders/subtractors.
        
           | jecel wrote:
           | It also only implements 3 registers, not 16 (RV32E) or 32
           | (RV32I), though it might count as 4 since register 0 is
           | hardwired to a 0 value.
           | 
           | But using the RISC-V instructions means that all kinds of
           | existing tools will work just fine for them as long as their
           | programs keep within the limitations. No need to write their
           | own assemblers and such.
        
       | [deleted]
        
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