CELL (diagrams from IBM)

1
CELL(diagrams from IBM)

• Andrew Williams
• A.Williams_at_bolton.ac.uk

2
CELL partners

• Sony, IBM, Toshiba
• We all know why Sony wants the CELL
• What is IBMs angle?
• What about Toshiba what do they want out of the
  CELL?

3
CELL chip image
What is this?
4
PPU

• Power Processing Unit
• Where might you have expected to find one of
  these a couple of years ago?

5
SPE questions

• Each SPE has 128 128-bit registers
• What is a register anyway?
• Name an example from an x86 compatible CPU
• How many bytes per register?
• 128-bits seems a lot (modern desktop CPUs have
  64-bit registers)
• Why does it need 128-bit registers?

6
This is an SPE 256K?? What the.?!
7
Multiplying a matrix by a vertex

• void Matrix4fmultiply(const Vector4f vec4f,
  Vector4f resultVector)
• float vD (float )vec4f.data // Just for
  convenience
• resultVector-gtdata0 data0vD0
  data1vD1 data2vD2 data3vD3
• resultVector-gtdata1 data4vD0
  data5vD1 data6vD2 data7vD3
• resultVector-gtdata2 data8vD0
  data9vD1 data10vD2
  data11vD3
• resultVector-gtdata3 data12vD0
  data13vD1 data14vD2
  data15vD3

8
SPE FP performance

• A CELL can handle 250GFLOPS as long as youre
  happy with SP
• Translate that into English
• What (according to IBM) is the likely performance
  penalty if you really want DP FP?

9
EIB
10
EIB questions

• What is the clock speed of the PS3 CELL?
• What is the clock speed of the EIB?
• How is the theoretical maximum bandwidth
  calculated?
• How many concentric data pathways (rings) are
  there in the EIB?
• How many data transfers can run concurrently on
  each ring?

11
EIB questions (continued)

• Give examples of the sorts of activity that could
  reduce the bandwidth of the EIB

12
RSX

• What is the RSX?
• Who developed the RSX?
• Which consumer PC product is most like the RSX?
• What does the design of the RSX say about the
  work that the SPEs are likely to be doing?