
AMD-K5 Processor
25
21062E/0—June 1997
AMD K86 Family BIOS and Software Tools Developers Guide
Preliminary Information
Normal BIST
The normal BIST is invoked if INIT is asserted at the falling
edge of RESET. The BIST runs tests on the internal hardware
that exercise the following resources:
I
Instruction cache:
Linear tag directory
Instruction array
Physical tag directory
Data cache:
Linear tag directory
Data array
Physical tag directory
Entry-point and instruction-decode PLAs
Microcode ROM
TLB
I
I
I
I
The BIST runs a linear feedback shift register (LFSR) signature
test on the microcode ROM in parallel with a March C test on
the instruction cache, data cache, and physical tags. This is
followed by the March C test on the TLB arrays and an LFSR
signature test on the PLA, in that order. Upon completion of
the PLA test, the processor transfers the test result from an
internal Hardware Debug Test (HDT) data register to the EAX
register for external access, resets the internal microcode, and
begins normal code fetching.
The result of the BIST can be accessed by reading the lower 9
bits of the EAX register. If the EAX register value is
0000_0000h, the test completed successfully. If the value is not
zero, the non-zero bits indicate where the failure occurred, as
shown in Table 12. The processor continues with its normal
boot process after the BIST is completed, whether the BIST
passed or failed.
Table 12. BIST Error Bit Definition in EAX Register
Bit Number
Bit Value
0
1
31–9
8
7
No Error
No Error
No Error
Always 0
Data path
Instruction-cache instructions