Initialization and POST
During initialization, LED and Beep codes are used to show the current step status and indicate initialization problems.
The Power on Self Test (POST) firmware is loaded into the CPU from the SROM at cold power on or after a hard reset. POST then performs the following functions:
- Puts the CPU, Bcache, memory, and I/O into a state which can be used by the operating system firmware.
- Runs some basic hardware tests to insure the operating system firmware can start.
- Memory testing
- Cache testing
- PCI data path test
- ISA data path test
- FlashROM test
- Reports via diagnostic LED and Beep codes.
- Starts the operating system firmware up - AlphaBIOS for Windows NT systems, and SRM for Tru64 UNIX and OpenVMS systems.
POST Hardware Testing
The POST hardware testing encompases the following checks and exercises.
- Memory testing:
- Ensures that each array consists of four identical DIMM's in every other socket.
- Checks the parameters in each SDRAM DIMM's onboard ROM for compatibility with system.
- Rejects whole array containing any incompatible DIMM.
- Ensures that there are identical DIMMs in each bank and rejects the array if the test fails.
- Performs "Checkerboard" test to detect data path errors. The pattern is alternated with each write to memory. The first 32MB of the first array is tested.
- Performs an addressing test to check all address lines in both arrays.
- The memory array is rejected if memory testing fails.
- Rejected arrays are rendered inoperative and not reported to the operating system firmware.
- If no usable memory is detected, a beep code will be heard.
- Cache testing:
- The data path integrity is tested.
- A thorough pattern test is performed on all Bcache SRAM cells.
- PCI data path testing:
- Reads the config registers in PCI configuration address space on both busses.
- Writes and reads back all registers being used to initialize PCI to the ISA bridge.
- ISA data path testing:
- Reads the ISA Super IO chip ID register.
- FlashROM testing:
- Performs a data path test.
- The contents of the FlashROM are fully check summed.
- If the FlashROM image is corrupt, a failsafe 1.44 MB diskette load procedure is started. Recovery firmware can be loaded from the emergency recovery floppy.