Clocks
Overview
A, A+, AB, B, B', C, C', D, D' chassis
Clock generation is based around one or two "DRCG-lite" (DRCG = Direct Rambus Clock Generator) clockgen ICs by varying manufacturers (Cypress CY2212 or TI CDCR61A).
DRCG-lite #1
All of these boards have an DRCG-lite IC which has an 18.432 Mhz XTAL connected to it's inputs. This DRCG-lite is set for a multiplier of 64/3 and thus creates a 393.216 Mhz clock for EE and RDRAM.
DRCG-lite #2
Additionally, all boards that have the original GS with metal heat spreader, CXD2934GB (GH-001, GH-003, GH-005, GH-007, GH-012, GH-014, GH-016), have a second DRCG-lite IC (also with an 18.432 Mhz XTAL) which is set to a multiplier of 16 to generate a 294.912 Mhz clock which is fed into GS. This additional DRCG is not found on their same-chassis-counterparts (GH-004, GH-006, GH-008, GH-010, GH-013) that use the second revision GS (CXD2944GB).
F, G, H chassis
Based around one "DRCG-lite" and one "GMCG" (=Graphics Media Clock Generator, e.g. Cypress CY24141) clock generator.
GMCG
The GMCG has a 18.432 Mhz XTAL and generates a 54 Mhz or 53.9 Mhz clock for GS (selection between 54 and 53.9 is done via control line from SSBUS controller, later from the SPU2+SSBUS-Controller combo IC) and also creates a 18.432 Mhz input clock for the DRCG-lite.
DRCG-lite
The main clock output of DRCG-lite is set for a multiplier of 64/3 and thus creates a 393.216 Mhz clock for EE and RDRAM. Additionally, DRCG lite generates a 9.216 Mhz clock signal for GS from the 18.432 Mhz input via a multiplier of 0.5.
I, J, K, L, M chassis
Based around one single DRCG-lite compatible clock generator with an 18.432 Mhz XTAL, generating a 393.216 Mhz clock, which additionally also generates the selectable 54 Mhz or 53.9 Mhz clock (e.g. Cypress CY22313).
N, P, R chassis
Based around one single clock generator IC with an 18.432 Mhz XTAL, similar, but not identical to the "GMCG" mentioned above. It outputs a 18.432 Mhz clock (for EE/the SoC of these chassis), a 25 Mhz clock (for the ethernet transceiver) and a (likely switchable) 54/53.9 Mhz clock (for GS, see above). Part number on IC case is always (?) 627G04LF. Not much else is known, since no public datasheet is available.