Service manual

If a processor’s yellow LED is OFF and the six red LEDs show an error
code in the range 1–22 (hex), the power-up self-test failed and the processor
board is bad. On the self-test console display, the processor shows a minus
sign (–) on the STF line.
After the power-up tests, each processor runs the CPU/memory tests. If a
test fails, the processor shows a minus sign (–) on the ETF line of the self-
test console display. With the first memory, LED error codes are numbered
from 25 to 38 (hex), to distinguish them from the power-up tests. For
example, assume that a processor fails self-test (yellow LED is OFF) and
shows the following pattern in the error LEDs:
TOP
(MSB) off 1
on 0 = 2
on 0
off 1 = 7
off 1
off 1
BOTTOM
The failing test number decodes to 100111 (hex 27), which corresponds to
the third CPU/memory test. If you then ran the ROM-based diagnostic 1
with TRACE ON, the last test number you would see displayed is T0003.
Each processor, after testing with the first memory, runs the CPU/memory
test on every other good memory module. (However, only CPU/memory
test T0002 is run.) If a failure occurs, the memory module is probably
bad, although the processor’s yellow light is OFF and the memory module’s
yellow light is ON. If several processors fail on the same memory, the
memory is certainly bad. Try using SET MEMORY to configure the bad
module out of the interleave set. For error codes higher than 38, consult
Table 3–2 to determine the failing memory.
The last series is the DWMBB tests. If one fails, the top six LEDs contain
an error code, although the processor’s yellow self-test LED is ON (because
the CPU itself has passed). The failing error code (converted to decimal)
corresponds to a test number in Table 7–5. Note that only the boot processor
performs the DWMBB tests, so the red LED next to the yellow LED is OFF.
<REFERENCE>(xyp) Scalar Processor 3–23