The same CPU and FPU are sued on the KA630cpu (uVAXII)
and in early
microvax3100s so any of them should compare.
I have a uVAXII which I'll be getting to eventually - right now it's
not running, but I hope to change that eventually :-)
Is it possible that someone has overclocked the that
I don't think so, as all the clocks (5Mhz, 40Mhz and 69Mhz) are
right where they should be in frequency.
FYI: gate leakage would kill the chips not make it run
usual reasons for hot running are:
Excessive bus loads (capacitive or resistive)
Since the machine is a closed system for the most part the first is
most likely and the others are least likely.
I've checked the power and it's well within spec.
Clocks appeare to be where they should be.
Cooling fan is not binding, appears to be running at the
right speed, there are no abnormal obstructions to the cooling
I may add that over 60C is way too hot at the heatsink
and the die
due to thermal resistance will be hotter.
I'm trying to pull down one of my uV2ks and fire it up.
I pulled out NETBOT:: a 12mb uV2000 with a RD53 and booted it with the
case off to get the temp and the hotter of the two chips stabilized
at 58C +- a tiny bit while running VMS 5.4-3.
Thanks! that at least tells me I'm not chasing an imaginary fault. At
82C mine is running significantly hotter than yours.
I've partially convinced that the FPU is bad, but I don't have hard
evidence/specs to confirm or deny this theory. Here's some of the
factors which lead me to this hunch:
There is some loading of the 40Mhz clock line going on (this is the
one going to the CPU and FPU). With W4 removed (disconnects the 40Mhz
clock at the osc, can) I measure a peak voltage of about 3.4V - with
the jumper in (connected to CPU and FPU) it drops to about 2.3v ...
Both chips have a CLKO line - on the CPU, this outputs a nice fat
20Mhz signal. On the FPU it outputs only about 130mv - but the technical
manuals says this pin is not used on the FPU and it is a no-connect
(so why label it CLKO - it's a different pinout than the CPU). This
could be normal - I won't know until I get a chance to compare with
There are a couple of no-connect pins from the FPU which show what
appears to be a logic waveform at a very low level - possibly an
indicator of contention somewhere within the chip, possibly normal,
I don't know.
The CPU is obviously running, but I have no real proof that the FPU
us running other than that it passes the power-up '9' self-test. I
have no idea how comprehensive this test is, and how much functionality
is required to pass it. I do note that there are two series of accesses
which occur during the self-test, measured on the !EPS (External Processor
Select) line - this is a line running directly between the CPU and FPU
which is used to communicate with the FPU.
What I see are two accesses 200ns apart, then 800ns idle, followed by 13
acesses 200ns apart, followed by 1000ns. Then a long gap - I didn't measure
it, but it's several ms. The second series of accesses is identical except
that there are 14 accesses in the middle stretch instead of 13 (all 200ns
apart). This would suggest that during the test it has at least issued a
command ... But I really don't know.
The extended system tests 101, 102 and 80000106 will not test the FPU -
this may be normal, I don't know. The docs say they will test all hardware
which is installed - this may mean that the FPU is not being full detected...
I don't know.
The CPU is obvously running - the FPU may or may not be, however it is
directly connected to almost ALL signals in parallel with the CPU - if it
were failed in a heat-generating way, it may well be loading the CPU and
causing it to get hot as well - the CPU does run slightly cooler than the
I think I've done about all I can do at this point - I see some suspicous
signals, but without real signal diagrams, or another system to compare it
to I can't confirm or deny a particular fault - I think the system is going
to have to stay on the shelf until I locate another one to make comparisons
Thanks for everyone for the great ideas and assistance.
dave06a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Collector of vintage computing equipment: