Marc wrote:
Could you check the ripple voltage on the +5V rail with a scope?
Yes, I did. Worst case when running OS-9 and "dchecking" the harddisk:
+/-30mV. After reset running 167-Bug and Microware ROM without activity
of the harddisk or other VMEbus cards: +/-20mV. This seems to be
acceptable. The power supply is a little bit oversized :-) Actually the
cards consume approx. 9A @5V, the power supply can deliver up to 30A @5V
(18 years ago, but moderate "mileage").
The scope was connected to Vcc and GND of the 48T08 (NVRAM).
Meanwhile I examined 15 MVME167s: most of the 48T08 internal batteries
are dead. I opened the first one and installed an external fresh
battery. There is no difference of this rubbish send to my terminal
depending on the state of the NVRAM chips.
But probably this is a "regular" timing problem of the Microware
software, means an old problem. When I plug in the Microware ROMs into
sockets U1 and U2 without Motorola's 167-Bug the Microware code
initializes the I/O in a correct way. I don't see the rubbish in this
case.
And there seems to be another problem at the interface between Motorola
code and Microware code. Nearly every time after cold or warm reset the Motorola code starts twice.
Conclusion: I will live with that situation. If I need a system booting
save after reset I will insert just the Microware code without
Motorola's 167-Bug.
Ralf
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