seismologist
Regular
What would it mean? Performance wise
So lets say the PS3 were to ship with 8 SPE's enabled
- Thread starter seismologist
- Start date
So let's say this is completely pointless speculation, because it won't.
Besides, this has been discussed in tons of other threads in the past, use the search function... This may seem as a curt, boring reply, but really. There isn't anything to discuss here that hasn't been said many times before.
Besides, this has been discussed in tons of other threads in the past, use the search function... This may seem as a curt, boring reply, but really. There isn't anything to discuss here that hasn't been said many times before.
If it were to happen, the performance profile would (in a theoretical, abstract sense) look like this:
Workload code is limited by PPE: pretty much no change, possibly slightly, undetectably, worse if the PPE is forced to worry about the extra SPE. It may be that many of the first wave of PS3 titles will have the PPE as a bottleneck. It should get better as people learn to balance the workload or offload more onto the SPEs.
Workload limited by memory bandwidth: pretty much not much change.
Workload limited by the GPU: pretty much not much change.
Workload spends most of its time waiting on the user or IO: pretty much not much change.
Workload limited by the SPEs: considering one SPE is reserved by the OS, the improvement would be in the best case proportional to the increase from 6 to 7. In anything but weirdly pathological code that for some reason is just bad on 6 SPEs but finds that the extra SPE is just barely enough to fix the issue (possible, but more of a sign of a strange problem or bad coding), the best that could be hoped for is slightly less than a 1/6 improvement.
Last edited by a moderator:
8/7~=1.143
In other words: It will rain blood and bone. Dreams will be shattered.
inefficient
Veteran
oh nm..
Less than 15% performance gain only on situations where the SPEs are the limit. Which i don't think happens very often as you'll be slowed down by bandwidth much sooner.
About 25 extra GFlops peak
(he says continuing this rather silly thread where the obvious is pointed out in as many different ways as possible
)
(he says continuing this rather silly thread where the obvious is pointed out in as many different ways as possible
)Not sure if people have seen this video with an video interview with Jim Kahle, IBM's Chief Architect & Chief Scientist for Cell Technology. If you forward to 4.00 min you will fastrack to his interview. He CLEARLY says at 4.55 the PS3 will have 9 Cores. The interviewer asks him again & he verifies 9 Cores again. Sorry if this video interview has already been seen & the 9 core possibility debunked.
http://www.youtube.com/watch?v=gV_95-rmYNo
Archy
http://www.youtube.com/watch?v=gV_95-rmYNo
Archy
Last edited by a moderator:
But he's wrong.
Last edited by a moderator:
Cell on PS3 does have 9 cores. As in, there are 9 independent cores in there (1 PPE + 8 SPEs). Only 8 work though (1 PPE + 7 SPEs).
That kinda depends on what you consider to be a core. Is it a core if there's a hardware fault that stops it working? Not every 1:7 PS3 Cell is going to have a working core disabled; some, quite possibly all early on when yields of 1:8s are rare, will have a broken SPE, at which point I don't think it can be counted as a core.he never says 9 working cores
Megadrive1988
Veteran
depending on the core clockspeed of the entire CELL processor, if the 8th SPE was working, it would add an extra 25~32 billion floating point operations per second. in PS3's case, about ~25 GFLOPs.
The PS3 Cell processor will have have 9 cores. However 1 SPE will be disabled for redundancy. That means better yields and better economy. It can go as either of these examples.
1) The Cell processor you get with your PS3 has 1 PPE + 7 enabled SPEs+ 1 disabled functional SPE
or
2) The Cell processor you get with your PS3 has 1 PPE + 7 enabled SPEs +1 disabled and broken SPE.
Either way, the PS3 will use 8 cores out of 9.
1) The Cell processor you get with your PS3 has 1 PPE + 7 enabled SPEs+ 1 disabled functional SPE
or
2) The Cell processor you get with your PS3 has 1 PPE + 7 enabled SPEs +1 disabled and broken SPE.
Either way, the PS3 will use 8 cores out of 9.
