On Mon, Mar 18, 2013 at 10:10 AM, Troy Benjegerdes <[email protected]> wrote:

> If registers are precious, why not add more? .. what is the relative cost
> (in terms of latency, silicon area, and energy) to double the register set
> size?
>

For CPUs, 32 was found to be optimal by some paper published back in the
early 90's, I think.  16 was a second best, while 64 had diminishing
returns.  I'm not sure how this applies to GPUs, however.  One problem with
doubling the RF size is that you slow it down.


>
> So what if we have 8 'bitbucket/constant' registers of these most used
> constants, and then instead of hardcoding the constants, make them be
> something the application can load.
>

This would be a good alternative to immediates.  Somes CPU architectures
don't/didn't have immediates.


>
> As for the dependency issue, I think the point of the bitbucket register(s)
> was that they have none, and we throw away all writes going to those
> registers.
>

It's a good alternative to the 'wr' bit in the ISA I posted.



-- 
Timothy Normand Miller, PhD
Assistant Professor of Computer Science, Binghamton University
http://www.cs.binghamton.edu/~millerti/
Open Graphics Project
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