Kara (karaardalan.delete@this.gmail.com) on August 27, 2022 11:18 am wrote:
> Björn Ragnar Björnsson (bjorn.ragnar.delete@this.gmail.com) on August 27, 2022 11:07 am wrote:
> > Rayla (rayla.delete@this.example.com) on August 27, 2022 10:35 am wrote:
> > > Nobod (Nobod.delete@this.nospam.com) on August 27, 2022 9:21 am wrote:
> > > > Chips & Cheese analyzes Tachyum’s Revised Prodigy Architecture
> > > >
> > > > The new architecture is more traditional and more likely to work. Unfortunately it is trying to address
> > > > both HPC and datacenter server markets, but isn’t better than the alternatives at either job.
> > >
> > > So... A somewhat unbalanced OoO design (gshare predictor, only 96 physical regs), a pair of massive vector
> > > units, tiny total caches per core (1MB is fine as an L2, but in the absence of a dedicated L3 it's awfully
> > > small unless 32+ cores are inactive, isn't it?), clock
> > > targets that can politely be described as optimistic,
> > > and a memory interface far slower than those present in GPUs in a similar FLOPS range?
> > >
> > > What am I missing?
> >
> > I don't think you're missing anything. It appears that the Chips and the Cheese
> > got to imbibe Tachyum kool aid directly from the fount after which they seem to
> > be slightly giddy without being totally inebriated.
> >
> > Ian Cutress's video piece with the c&c's is basically a waste of time if you read
> > the chipsandcheese text.
> >
> > What we are being presented with now is, in today's tech, for all intents and
> > purposes a pretty conventional design. Hopefully they'll have something interesting,
> > hopefully they'll have something :) but I'd be amazed (even delighted) if they live
> > up to a fraction of their hype.
>
>
> The vector coprocessors are still very much vliw and denver I don't get how no one's mentioning
> it. They don't get rob! An rob for such thing would quadruple the size of the entire core.

Pretty sure the 256-entry "Scheduler/Instruction Control" acts similar to a ROB.

They claim to use a checkpointing system to do OoO, but all modern high-end OoO processors already use checkpointing.
I believe the bottom line is that their micro-architecture relies much more on checkpointing. My guess is that instruction retire on Prodigy can only be performed on instruction marked by a checkpoint, which groups instructions into retire instruction groups.
This should greatly simplify rollback but requires inserting checkpoints where they would usually not be required.

But anyway if you are doing OoO execution (with exception or interrupt) then you have to track all instructions between 2 "retire-points" (just like a ROB) no matter if retire can be done on any individual instruction or on instruction groups marked by a checkpoint.

Also, a ROB does not quadruple the core area.