Performance Verification Boot Procedure - HP 64100A Service Manual

Model 64100A - Performance Verification
"XY" corresponds to the UI of the failing RAM.
Depending on which RAM is failing, the display
could be affected. Evidence of this is a random
pattern on the CRT or incorrect spelling of
messages. For this reason the accuracy of a RAM
test failure is always suspect. Because the RAMs
are 1 bit wide, 16 of the 32 RAMs are used to store
display information. U23-U30 and U38-U45 on the
display controller board are used for display
memory. Thus, if any of these 16 RAMs is failing,
the display will be unintelligible to various
degrees. If this occurs see display section IV, SA
table E, to troubleshoot the outputs of the RAMs.
4-11. PERFORMANCE VERIFICATION BOOT PROCEDURE.
a. Place the control source switches in the Performance verification
position shown on the control source label on the rear panel.
See Figure 4-1 for the switch locations.
b. Turn power off and then back on. The display test pattern,
figure 4-2, should be on screen after the boot tests. However,
there are several steps that occur before the display test
pattern is shown.
MF 4-6
1. Suspend operation of the PHI chip (U20 on I/O board) and
take it off line.
2. Initialize the CRT chip (U33 on Display Control board).
3. Enable the display and sound the beeper once.
4. Disable interrupts.
5. Disable CPU direct memory access.
6. Clear base page RAM (FOOO- FFFF hex).
7.
Set up interrupt vector.
8. Clear keyboard power up interrupts.
9.
Clear display screen.
10. Set up and enable keyboard interrupts for display test.
11. move cursor off screen.
12. Determine what local mass storage is present so the
correct softkey will appear.