Can someone explain me about these bandwidth numbers in Cell

[marconelly!]

OK, first published information about the bandwidth specs can be found in here and it says:

As previously announced, the off chip I/O interface is Rambus Redwood and the memory interface is XDR. Similar clocking/deskewing schemes. Looks to be about ~50 GB/s BW to memory, and 50~100 GB/s to I/O.

This seem to be in agreement with anothe press release from Rambus, talking about 100GB/s to I/O.

Then, on another slide, it was publicized that Cell would have 25.6 GB/s (per chip?) and ~75GB/s to I/O, if I remember correctly

So, why are these numbers so conflicting?

Also, and this is unrelated, can we be sure about the total amount of memory in PS3 (256MB), based on the size of individual chips they plan to use?

 

[London Geezer]

Re: Can someone explain me about these bandwidth numbers in

OK, first published information about the bandwidth specs can be found in here and it says:

As previously announced, the off chip I/O interface is Rambus Redwood and the memory interface is XDR. Similar clocking/deskewing schemes. Looks to be about ~50 GB/s BW to memory, and 50~100 GB/s to I/O.

This seem to be in agreement with anothe press release from Rambus, talking about 100GB/s to I/O.

Then, on another slide, it was publicized that Cell would have 25.6 GB/s (per chip?) and ~75GB/s to I/O, if I remember correctly

(1)So, why are these numbers so conflicting?

(2)Also, and this is unrelated, can we be sure about the total amount of memory in PS3 (256MB), based on the size of individual chips they plan to use?

(1) Cause no one knows at this point what's gonna be in the box.

(2) No, cause no one knows what's gonna be in the box yet.

 

[j^aws]

Re: Can someone explain me about these bandwidth numbers in

OK, first published information about the bandwidth specs can be found in here and it says:

As previously announced, the off chip I/O interface is Rambus Redwood and the memory interface is XDR. Similar clocking/deskewing schemes. Looks to be about ~50 GB/s BW to memory, and 50~100 GB/s to I/O.

This seem to be in agreement with anothe press release from Rambus, talking about 100GB/s to I/O.

Then, on another slide, it was publicized that Cell would have 25.6 GB/s (per chip?) and ~75GB/s to I/O, if I remember correctly

So, why are these numbers so conflicting?

Also, and this is unrelated, can we be sure about the total amount of memory in PS3 (256MB), based on the size of individual chips they plan to use?

There's a thread/ post on the front page about the XDR confusion,

http://www.beyond3d.com/forum/viewtopic.php?p=462167#462167

And about the FlexIO from Real World Tech,

...
What is known about the system interface of the CELL processor is that the FlexIO consists of 12 byte lanes. Each byte lane is a set of 8 bit wide, source synchronous, unidirectional, point-to-point interconnects. The FlexIO makes use of 96 differential signaling pairs to achieve the data rate of 6.4 Gb per second per signal pair, and that data rate in turn translates to 6.4 GB/s per byte lane. The 12 byte lanes are asymmetric in configuration. That is, 7 byte lanes are outbound from the CELL processor, while 5 byte lanes are inbound to the CELL processor. The 12 byte lanes thus provide 44.8 GB/s of raw outbound bandwidth and 32 GB/s of raw inbound bandwidth for total I/O bandwidth of 76.8 GB/s.
...

http://www.realworldtech.com/page.cfm?ArticleID=RWT021005084318&p=11

FWIW, the whole RWT article is a good technical read.

 

[Qroach]

Can someone explain me about these bandwidth numbers in Cell

um... no

 

[j^aws]

Can someone explain me about these bandwidth numbers in Cell

um... no

Bah...you lazy! ...Read the above article!

 

[hugo]

We'll know when Sony officially announce the PS3 in due time at E3.They can't announce everything yet for now as MS and Nintendo are watching them closely for every step they make in order to one up them.I would also want to know how many PPEs the Cell for PS3 will use and how much memory they put in is still not mentioned by them.Everything on the setup for the PS3 is still speculation.

 

[Megadrive1988]

Ive been confused over this first generation Cell's bandwidth myself.


~25 GB/sec is not very high, if it has to share that with the GPU.

 

[zidane1strife]

We'll know when Sony officially announce the PS3 in due time at E3.They can't announce everything yet for now as MS and Nintendo are watching them closely for every step they make in order to one up them.I would also want to know how many PPEs the Cell for PS3 will use and how much memory they put in is still not mentioned by them.Everything on the setup for the PS3 is still speculation.

If they could just use a BE, 1GB ram, and an equally beefy-PS heavy gpu, I'm sure it'd not be feasible to 1up'em... though it's probably unlikely.

 

[Megadrive1988]

We'll know when Sony officially announce the PS3 in due time at E3.They can't announce everything yet for now as MS and Nintendo are watching them closely for every step they make in order to one up them.I would also want to know how many PPEs the Cell for PS3 will use and how much memory they put in is still not mentioned by them.Everything on the setup for the PS3 is still speculation.

If they could just use a BE, 1GB ram, and an equally beefy-PS heavy gpu, I'm sure it'd not be feasible to 1up'em... though it's probably unlikely.

baw! why not use a dual-Broadband Engine
(thats eight Processing Elements, thus 8 PPEs plus 64 SPEs)
and 2 GigaBytes of 102 GB/sec (or ~204 GB/sec!) XDR

plus an Nvidia GPU with 128 pixel shader ALUs and it's own private
2 GigaBtyes RAM.


^___^