Computer tester from the BM9222 MASTER KIT: troubleshooting in the PC system unit. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Measuring technology

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Computer tester VM9222 MASTER KIT, the appearance of which is shown in fig. 1 is used to diagnose malfunctions of personal computers such as the IBM PC or compatible with it [1].

Fig. 1

The tester is a computer expansion board that is installed in any free PCI slot (33 MHz) of the motherboard. It is designed to display POST (Power-On Self-Test) codes generated by the computer BIOS in a user-friendly way.

Technical specifications

1. Indication of POST codes: on the LCD display in two lines of 16 characters each (the first line is the POST code in hexadecimal form and separated by a dash is the BIOS type, the second line is a description of the error in the form of a running line).
2. Indication of PCI bus signals: LEDs on the front side of the board - RST (PCI reset signal) and CLK (PCI clock signal).
3. PCI bus supply voltage indicators: +5, +12, -12, +3,3 V.
4. Compatible with motherboards based on INTEL, VIA, SIS chipsets.
5. PCB size: 95,5x73,6mm.

Checking the PC system unit with a Post Card PCI tester

Checking the PC system unit using the Post Cord PCI tester includes the following steps:

1. Processor testing.
2. Checksum ROM BIOS.
3. Checking and initializing DMA, IRQ and timer controllers. After this stage, sound diagnostics become available.
4. Checking memory regeneration operations.
5. Testing the first 64 kB of memory.
6. Loading interrupt vectors.
7. Video controller initialization. After this step, diagnostic messages are displayed on the screen.
8. Testing the full amount of RAM.
9. Keyboard testing.
10. Testing CMOS memory.
11. Initialization of COM and LPT ports.
12. Initialization and test of the FDD controller.
13. Initialization and test of the HDD controller.
14. Search for additional ROM BIOS modules and initialize them.
15. Calling the operating system loader (INT 19h, Bootstrap), if the operating system cannot be loaded, an attempt is made to start ROM BASIC (INT 18h); on failure - system halt (HALT).

Passage of tests

When passing each of the POST tests, a special code is generated, which is written to the diagnostic register. The information contained in the diagnostic register becomes available for observation when the POST Card diagnostic board is installed in a free slot of the computer and is displayed on a seven-segment display in the form of two hexadecimal digits. The address of the diagnostic register depends on the type of computer, in older versions it is: ISA, EISA-80h, ISA-Compaq-84h, ISA-PS/2-90h, MCA-PS/2-680h, 80h, some EISA-300h. Laptops can issue POST codes via LPT or USB port.

Before using the tester, you must determine the BIOS manufacturer of the motherboard. This can be done either by a sticker on the BIOS chip, or by the inscriptions that are displayed on the screen by a similar working motherboard. In Russia and the CIS, the most common are BIOS firms AMI and AWARD. With the acquisition of some experience, already by the first POST codes, you can confidently name the BIOS manufacturer.

POST code tables are different for different BIOS manufacturers and, due to the emergence of new tested devices and chipsets, they differ even for different versions of the same BIOS manufacturer.

Historically, the values ​​of POST codes in the corresponding tables of BIOS manufacturers are given in hexadecimal form in the range OOh-FFh (0-255 in decimal), therefore, for the convenience of using such tables, it is necessary to ensure that POST codes are displayed in hexadecimal form.

In order not to make it difficult for readers to search for POST codes, the author gives them in a tabular form. According to the codes, you can draw a conclusion about a particular malfunction.

POST codes and their description

Here is a list of POST codes for troubleshooting (see table) on the example of a motherboard with BIOS from Award - AwardBIOS V4.51 PG Elite (see [2]).

In 1995, Award Software introduced a then-new low-level software solution, AwardBIOS "Elite", better known as V4.50PG. The checkpoint service mode has not changed in either the widespread version V4.51 or the rare version V4.60. The suffixes P and G denote, respectively, the support of the PnP mechanism and the maintenance of energy saving functions (Green Function).

Fig. 2

Consider the procedure for testing the system unit of a personal computer. After installing the tester in a free PCI-slot of the motherboard and turning on the PC power, the BIOS of the computer performs a serial poll of all devices included in the system unit (Fig. 2).

If all peripheral devices of the system unit are working, then after the download is completed, the inscription shown in fig. 3.

Fig. 3

If, however, various failures and errors occur during the operation of the PC, the tester displays the corresponding code. For example, in fig. Figure 4 shows a PC RAM error message.

Fig. 4

POST code	Description
Executing POST start procedures from ROM
WITH	Disable External Cache. Disable Internal Cache. Shadow RAM ban. Programming DMA controller, interrupt controller, timer, RTC block
С1	Determining the type of memory, the total volume and placement by line
sz	Verification of the first 256K DRAM for the organization of the Temporary Area. Unpacking BIOS in Temporary Area
С5	Executed POST code is transferred to Shadow
С6	Determining the presence, scope and type of External Cache
С8	Checking the integrity of programs and BIOS tables
CF	Determining the type of processor
POSTing to Shadow RAM
3	Disable NMI, PIE (Periodic Interrupt Enable), AIE (Alarm Interrupt Enable), UIE (Update Interrupt Enable). SQWV Programmable Frequency Generation Prohibition
4	Checking the formation of requests for regeneration of DRAM
5	Checking and initializing the keyboard controller
6	Testing the area of ​​memory starting at address FOOOh where the BIOS is located
7	Checking CMOS and battery operation
BE	Programming the configuration registers of the South and North Bridges
9	Initializing L2 Cache and Cyrix Advanced Cache Control Registers
0А	Interrupt vector table generation. Configuring Power Management Resources and Installing the SMI Vector
OB	CMOS checksum check. Scanning the bus PCI devices. Processor microcode update
OS	Keyboard controller initialization
0D	Search and initialization of the video adapter. IOAPIC setup. Clock frequency measurements, FSB setting.
0E	MRS initialization. Video memory test. Display Award Logo
0F	Checking the first DMA 8237 controller. Keyboard detection and its internal test. BIOS checksum check
10	Checking the second DMA 8237 controller
11	Checking the page registers of DMA controllers
14	System timer channel 2 test
15	1st Interrupt Controller Request Masking Register Test
16	2nd interrupt controller request masking register test
19	NMI Passivity Check
30	Determining the amount of Base Memory and Extended Memory Setting the APIC. Programmatic control of the Write Allocation mode
Preparing tables, arrays and structures to start the operating system
31	The main on-screen test of RAM. USB Initialization The Plug and Play BIOS Extension splash screen is displayed.
32	Setting up Super I/O resources. Programmable Onboard Audio Device
39	Programming the clock generator on the 12C bus
ZS	Setting the software flag to allow entry in Setup
3D	PS/2 mouse initialization
WE	Initializing the External Cache Controller and Cache Permissions
BF	Setting configuration registers chip set
41	Initializing the floppy disk subsystem
42	Disabling IRQ12 if no PS/2 mouse is present Performs a soft reset of the hard drive controller. Scanning other IDE devices
43	Initializing Serial and Parallel Ports
45	FPU coprocessor initialization
4E	Error message indication
4F	Request a password
50	Restoring a previously saved CMOS state in RAM
51	Allow 32 bit HDD access. configuring ISA/PnP resources
52	Additional BIOS initialization. Setting PHX Configuration Registers Forming NMI and SMI
53	Setting the DOS Time counter according to Real Time Clock
60	Installing anti-virus protection BOOT Sector
61	Final steps to initialize the chipset
62	Read keyboard ID. Setting its parameters
63	Correction of ESCD, DMI blocks. Clearing RAM
FF	Transferring control to the bootloader. BIOS executes INT19h command

Literature

1. Description "Device for repair and testing of computers - POST Card PCI" BM9222.
2. Award BIOS Error Codes - award.com.
3. Magazine Repair and service

Publication: radioradar.net

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