[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [f-cpu] F-CPU vs ALPHA



hi !

nicO wrote:
> 
> >FC0 issues in-order all the instructions that are considered as valid.
> >if a trap occurs, it must NEVER enter the pipeline (because of the OOO
> >completion, it would become a nightmare to rewind the pipeline !!!).
> 
> !!! "rewind the pipeline !" You just have to bypass the write back stage !

i told you i was really lazy :-)

> >Currently, FC0 uses two addressing spaces : "private" space where the CPU
> >is the only master (cache coherency is straight-forward) and "outside world"
> >where all the accesses are in-order and uncacheable.
> 
> I don't think it will be very interresting (too slow). It will be much
> interresting to manage this inside the VM unit by page (the page will
> have the information of none caching, none registering,...). And then a
> decoder will send the data thought memory port or fbus port.

there will be something like that.
however i have to solve a bunch of problems concerning the
"execution pipeline" first.

> >Use semaphores that are mapped in the SRs !
> In all case, we need to write something in memory or to touch something
> in the VM unit.
why ? a semaphore is a semaphore, a flag if you want.
whether it is implemented in memory or with a dedicated HW in
a different addressign space, is "implementation dependent".


> So it's just pushing the problem away !
and if possible where it doesn't disturb us :-P

the L/S unit is optimised to allow high bandwidth through
cache-line width packet transfers, accessing single bytes
in scattered order is a good way to "kill" your memory subsystem
and the speed of your synchronisation.

> More generaly, i find the text very agressive against Alpha.(the 2 first
> sentences of the text, for example). We should never forget that alpha
> work since 10 years and fcpu is in it's very beginning. So this kink of
> speech could make laught a futur investor in the fcpu, never forget
> that.

i think that you know that i am not "agressive" and that i respect the
ALPHA. I have two expensive books about it and unfortunately no
Alpha server at home.

We can still discuss whether Alpha is dead or not. CPQ will keep
Alpha alive artificially as long as IA64 is not a serious competitor.
that is enough for me : it's just marketing and financial manipulation,
the ALPHA engineers have a very reduced freedom of decision now,
because they know that it will be dropped after the 364.

So i could say : Alpha is dead as much as F-CPU is alive.
it's time to learn alpha's lessons, i think.

> nicO
> *************************************************************
WHYGEE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*************************************************************
To unsubscribe, send an e-mail to majordomo@seul.org with
unsubscribe f-cpu       in the body. http://f-cpu.seul.org/