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8RDA+: low voltage but stable?

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rogerdugans

Linux challenged Senior, not that it stops me...
Joined
Dec 28, 2001
Location
Corner of No and Where
I recently got an 8RDA+ (Rev 2) and am currently a bit surprised by something:

I am overclocked a decent bit and my 5v rail is down around 4.81 volts yet the system is completely stable!!!

I am not surprised that the voltage has dropped considerably as I am using a cheapo psu for the moment, but the fact that the system is completely stable with a 5v rail reading 4.81 does surprise me a lot: every other AMD mobo I have used started having stability problems around 4.84 volts, yet this one has been running without issues for over 48 hours at 4.81.

Has anyone else run one of these with a low 5v rail?
I am just curious to know if this is me getting lucky or common with these boards.
 
what kind of fsb does yours do? got my revision2 8rda+ last week.



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Oops :(
I really meant to put more info in my first post but I got sidetracked ;)

So far I have not really pushed the system hard: I have a third rate heatsink with a Delta fan on the chip- and I am not sure which chip it is, lol: I have 2 1700s that don't do great and two XP1600 agoia y 0213s that do.
I am only certain that one of the agoias is in my main rig.......


Right now the FSB is at a mere 178 with pc2100 ram at 100% speed. I know that stick of ram will do a bit more- about 180 and a few, but I have some pc2700 and pc3200 in another rig that needs to move over:)
I hope to have time this weekend to test the limits of the board a bit more, but I am still wondering just how much of a limit the psu is going to be......
 
well mine is running at 4.75v...

Its not the powersupply, my PSU is putting out a nice steady 5.1v (Sparkle 400w). I have active cooling on my mosfets, but not on the voltage regulator chip above them (thats a soon-to-come project).

In your case with a not so good powersupply it may limit you. Also, definetly cool the mosfets. Before i did that i couldnt raise the vcore over about 1.85 without it crashing. After i could go to 2v stable (this was with my 1600+).
 
How are you cooling your mosfets, WyrmMaster? I'm going to put some hacked up RAMsinks on mine pretty soon - I'm hoping I can get some extra FSB mhz out of it.

Also, the rule of thumb is that if your rails are within 5% of spec, you're ok. 4.75v is just on the edge.
 
i hacked up an old CPU heatsink, and i have had a 50mm fan on it (i think im going to go to an 80mm though, get better cooling on them and also on everything else in that corner of the board)

I dont know if you will get any more FSB speed for it, but if you cpu will go faster with more voltage then it should help you there.


another thing, i just did the 5v mod on my board (only one lead to one of the mosfets) and it didnt change my voltages at all under load. When i first boot up the bios shows 5v a bit higher than it used to be, but in windows under full load its right where it was.
 
I'm going to go nuts with the RAMsinks and stick them all over the board. I want to reach 200mhz but I think the only way to do that will be to do the vdd mod. So extra cooling will be a last-ditch effort.

Do you have a link or a guide for the 5v mod? I'd like to hear about it.
 
check the power supplies / cases forum, hoot has a great stick on it. Its a bit tough to do and heatsink them as well, you need to be careful to keep it below the top of the mosfet so you can fit the heatsink on. What i did after i finally got it to stick (soldering it was a pain) was put a small piece of electirical tape over the solder joint (jsut pressed down on top) to keep it away from the heatsink. I dont think it would matter though if i did touch the heatsink, as long as nothing else is touching the heatsink.

Also, be sure to cool the voltage regulator chip above the mosfets. That sucka gets HOT. I just put a heatsink on mine, and i seriously cant keep my finger on the heatsink for more than a half a second or it would burn me. Definetly need that 80mm over the entire area. However, i am running at a new high, 2400mhz, 1.9v core (my barton kinda sucks). Not sure how stable it is but its atleast running windows and folding.
 
Did you check with a multi? I think my 8rda 2.0 read like 5.1 but it was really 5.35v.. btw my 8rda+ rev2 did 230+ fsb with 1.6vdd.. 3.27 vdimm

ss
 
yah, it reads kinda low with the multi meter on the mosfets too, not quite as low as windows reads it, but low.

turned out to not be stable at 2400, no mater what i did... Maybe it needs more voltage than i can give it. I dont know. One thing thats strange is my 5v drops a bit when i put a fan on the mosfets... Actually with no heatsinks at all on them it started out much higher than it usually runs, although it does slowely drop to the normal level.
 
Finally posting up in this thread again ;)

I have checked the molex voltage and it reads the same as MBM/BIOS so I am getting a true reading, and it is lowere than I have seen stable with any AMD chip since a K62- 4.76v and rock solid stabilty.

I have still not pushed the board too hard because I have too many other things to do lately and nowhere near enough time, but I will say that this is a great board:
cpu is an XP1700 (Pally) that would not go above 1740 or so in any other board- including a highly modified 8KHA+ with adjustable vcore,vdimm and 5v psu rail.
In the 8RDA+ it is running at 1810 with a 4.76 5v rail and has passed prime for 24 hours with no issues.

If I ever have spare time.....adding some sinks to the mosfets and some of the other hot chips will happen.
I may put a better chip and psu in there and see what it does sometime too. :)
 
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