MSI K8N Neo DOT screws up MSI 5900XT

Question

Greeings,
I've asked this question in the motherboard section...now I'd like to try the graphics card section to see if anyone can explain some odd behavior I've seen with the following combo:
MSI K8N Neo Plat
with
MSI 5900XT
Normally, I run the 5900XT with manual overclock:
390/700 --> 490/780.
Since the increase in GPU is higher than the increase in memory,
I prefer manual overclock to DOT on the graphics card.
Anyway, 490/780 is rock solid...sometimes even up to 510/820 is,
but I keep it at 490...
Anyway, that's all well and good, but recently I've tried using
the motherboard's DOT feature to bump up CPU and memory speed
(but which should leave video card performance unaffected, right??)
When I apply a tiny 3% DOT (again, this is on the motherboard,
so I'm not DOT-ing the 5900XT card...), suddenly the video card
will crash (or freeze for 10 seconds and then run very slowly, an
indication that it entered throttle safe mode).  This is really strange.
To investigate, I did the following experiment with aquamark3:
a) no overclocking anywhere: score of about 37500
b) same as (a) but set moboard HTT/FSB from 200 to 206: 37610
    Seems reasonable to get just a slight speedup, since this step
    doesn't boost video card performance, which is presumably the
    limiting factor.
c) same as (a) but use 3% DOT on the moboard. This has the effect
    of boosting the HTT/FSB from 200 to 206, which of course should
    yield about the same performance as (b). But I get about 40000 (!)
This experiment indicates that a little 3% DOT on the motherboard has
the effect of also (drastically) overclocking the video card (and to
make it stranger, the video card overclock is far more than 3%...we're
talking 3000 aquamarks which is more like a 9% graphics card overclock!!)
That's probably why a little motherboard DOT combined with
my usual 490/780 5900XT overclock froze up the video card and causes
it to enter safe mode.
BUT the question is: WHY should motherboard DOT be overclocking
the graphics card in the first place?  Has anyone else seen this?  Is it
intentional?

Answer 1

Using RivaTuner, which plots video card GPU and mem mhz in real time, I'm able to absolutely confirm that turning on either 1% or 3% DOT on the motherboard (k8n) has the effect of dramatically overclocking the video card (a 5900xt)
Strangely enough, the overclock of video card overclocks the GPU mhz but leaves the video card mem speed unchanged. Again, I'm using RivaTuner to make these claims.
I've tried with BIOS 1.2, 1.3, and 1.4b2
Examples:
gfx card set to defaults (390/700). moboard set to 1% DOT.
RivaTuner shows that aquamark3 starts at 390/700 for a few moments, then it jumps up to 429/700. Should have stayed at 390/700.
example 2: 400/700...actually runs at 441/700 (again, a 10% GPU overclock)
weird example 3: 405/700...stays at 405/700 (no GPU overclock)
example 4 (the killer): 410/700...aquamark3 freezes at frame 873 (graphics card goes into throttle mode). What does RivaTuner show?
It shows the graphics card running at 526.5, which is waaaaay over spec and is over a 28% overclock beyond what I asked for! (which was 410)
And where does the 28% come from?  At least in previous runs it was either 0 or 10%, which at least I could plan around if it was consistent...but 28%?!
Bottom line: MSI K8n neo plat motherboard DOT (even at just 1% DOT) has a nasty side effect of also overclocking the GPU core. This is bad, but could be worked around if the amount was consistent. Unfortunately, the amount isn't consistent (usually 10%, but sometimes 0 or even 28%)
I'm not sure if MSI is doing this to look good in anandtech/tomshardware benchmarks, or if it's a real bug...