Thermal sensors
Overview
The PS2 has a thermal sensor IC in proximity to the EE (or EE+GS, depending on the revision).
On consoles with a Dragon MechaCon (SCPH-500XX and later), the thermal sensor is connected to the MechaCon and the temperature can be read from software. On earlier consoles, the thermal sensor is connected to the SysCon and the temperature can (currently) not be read from software. GH-001 and GH-003 use a simple thermostat instead of a temperature sensor.
Texas Instruments LM56
Thermostat, 2 digital outputs for 2 configurable temperature thresholds, used in conjunction with NJM062V op-amp
Used on GH-001 and GH-003
Texas Instruments LM74
SPI/Microwire temperature sensor, 13 bit, 8-pin SOIC-8
Used on GH-004, GH-005, GH-006, GH-007, GH-008, GH-010, GH-012, GH-013, GH-014
Texas Instruments LM70
SPI/Microwire temperature sensor, 11 bit, 8-pin VSSOP-8
Used on GH-015, GH-016, GH-017, GH-019, GH-022
Texas Instruments LM71
SPI/Microwire temperature sensor, 14 bit, 5-pin SOT-23, SMD-code: T16C. Some boards that use the LM71 also have alternate solder pads and wiring for a LM20.
Used on GH-023, GH-026, GH-029, GH-032, GH-035, GH-036, GH-037, GH-040, GH-041
Texas Instruments LM20
Analog output temperature sensor, 5-pin SOT-323/SC-70, SMD-code: T2B. Analog output connected to Dragon-MechaCon, which probably has an internal ADC for this. Some boards that use the LM20 also have alternate solder pads and wiring for a LM71.
Used on GH-051, GH-052, GH-061, GH-062 (also likely on GH-070, GH-071, GH-072, but unconfirmed)
Seiko S-58LM20A
Analog output temperature sensor, 4-pin SC-82AB, SMD-code: DRE. Analog output connected to Dragon-MechaCon, which probably has an internal ADC for this. Drop-in replacement for Texas Instruments LM20 that can be mounted on the same footprint with 1 pin less (which is NC on Texas Instruments LM20).
Used on GH-072 (also likely on GH-070, GH-071, but unconfirmed)
PS2 hardware in PS3
COK-001 has unpopulated pads for a thermal sensor next to EE+GS. COK-002 doesn't have any temperature monitoring capabilities next to GS.