Re: mips64 on port-cobalt

[Andy Ruhl <acruhl%gmail.com@localhost>]

On Fri, Dec 18, 2009 at 9:54 AM, Alex Pelts <alexp%broadcom.com@localhost> 
wrote:
> Not that this should stop anyone from trying, but I am not sure Qube
> will gain anything by going 64 bit. While RM5231 processor is certainly
> 64bit, the system interface is 32bit so for every data memory read and
> write it will require 2 accesses in 64 bit mode. Also data cache will be
> effectively cut in half if most of the structure size would double due
> to going to 64 bit.
> Even all of this is mediated somehow, context switch will become 2x
> slower due to doubling amount of data that needs to be saved and restored.
> So aside from satisfying curiosity the 64bit mode will be detrimental to
> Qube performance. And this thing already is not a speed daemon. Plus
> this system can't physically accommodate enough memory to need 64 bits.

Sometimes when you're doing research and trying new stuff you learn
something you didn't expect.

I'm not sure what the chances of that are here, probably not super duper good.

I always thought the whole point of working with this wacky stuff was
to make the MI code stronger.

Andy