Acer Veriton Z291G Service Guide - Page 56

System Internal Inspection 1. Turn off the power to the computer and all peripherals. 2. Unplug the power cord from the computer. 3. Unplug the network cable and all connected peripheral devices from the computer. 4. Place the computer on a flat, steady surface. 5. Remove the TV stand and the rear cover. 6. Verify that the processor, memory module(s), and expansion board(s) are properly seated. 7. Verify that all power and data cables are firmly and properly attached to the installed drives. 8. Verify that all cable connections inside the system are firmly and properly attached to their appropriate mainboard connectors. 9. Verify that all components are Acer-qualified and supported. 10. Reinstall the rear cover and the TV stand. 11. Power on the system. If the cause of the failure is still can not be determined, review the POST messages and BIOS checkpoints during the system startup. Checkpoints A checkpoint is either a byte or word value output to I/O port 80h. The BIOS outputs checkpoints during bootblock and Power-On Self Test (POST) to indicate the task the system is currently executing. Checkpoints are very useful in aiding software developers or technicians in debugging problems that occur during the pre-boot process. Viewing BIOS Checkpoints Viewing all checkpoints generated by the BIOS requires a checkpoint card, also referred to as a POST card or POST diagnostic card. These are ISA or PCI add-in cards that show the value of I/O port 80h on a LED display. Checkpoints may appear on the bottom right corner of the screen during POST. This display method is limited, since it only displays checkpoints that occur after the video card has been activated. NOTE Please note that checkpoints may differ between different platforms based on system configuration. Checkpoints may change due to vendor requirements, system chipset or option ROMs from add-in PCI devices. Boot Block Initialization Code Checkpoints The boot block initialization code sets up the chipset, memory, and other components before system memory is available. The following table describes the type of checkpoints that may occur during the boot block initialization portion of the BIOS. Checkpoint Before D1 D1 D0 D2 D3 Description Early chipset initialization is done. Early super I/O initialization is done including RTC and keyboard controller. NMI is disabled. Perform keyboard controller BAT test. Check if waking up from power management suspend state. Save power-on CPUID value in scratch CMOS. Go to flat mode with 4GB limit and GA20 enabled. Verify the bootblock checksum. Disable CACHE before memory detection. Execute full memory sizing module. Verify that flat mode is enabled. If memory sizing module not executed, start memory refresh and do memory sizing in bootblock code. Do additional chipset initialization. Re-enable CACHE. Verify that flat mode is enabled. 48 Veriton Z290G AIO Computer Service Guide