Low Voltage Questions...

Hi all!

While I've been waiting patiently for the dual core xeons to be released, I've become increasingly interested by the o/c's LV xeons are able to achieve.

I'm not too familiar with LV processors and was wondering if the potiental o/c of 3.0Ghz LV xeons would be worth the trouble getting?

If you get D1 or M0 stepping LV (1.3volt default vcore) or 1.5volt (standard) 533fsb xeons and the right motherboard,
a 3.0ghz overclock is pretty typical, with most topping out around 3.2-3.4ghz (depending on the chips, memory, and cooling you have also).


By the way - welcome to the forums!


Since you're a new member, you won't be able to access the classifieds here for a while, but if you can find used equipment through other sources (such as ebay) then you can build a decent SMP machine for a great price.


Of course one thing to ask yourself if you really need an SMP machine, especially now that another alternative (dual-cores) are available.

Is there any reason besides price that older D and M steppings are used?

my D1's are good for 3.4ish

Are you talking about the new Nocona based LV Xeons? Or are you talking about the older Prestonia LV's ?

I don't think that the prestonia's ever had an 3ghz LV.. The Nocona's might.

The reason people use the D1 or M0 stepping is that there were some specific chips that had the perfect recipe for great clocks.. Say the 2.4ghz LV D1's or M0's... They had an fsb of 133mhz, and a multiplier of 18. With tricks, you can boot up the chips at 200mhz fsb, but the problem is that Xeons will always POST at FSBxbootstrap multiplier. This means that you need a decent chip with a low multiplier to ever have hopes of running at 200. A 3.06 chip will be 133x23. To post this at a fsb of 200, you will end up running for a few seconds at 4.6ghz (200x23) Ouch. The 2.4ghz chips are the best for this, because a lot of xeons can at least post at 3.6, then load up a new multi.

Now, with Nocona's (naitive 200fsb) you just want a high multi. The LV's will be good, because they might give you more overhead (think Mobile Barton) Crank those volts back to normal, and you might have a nicely clocking chip - problem is, you want a high multi because xeons are still hard to push high into the fsb range. MAX you should be able to reach is around 250.. and thats a big maybe.. So to get really high clocks, you want a high multi.


So.. back to your question: Clarify exactly which chip you are looking at :- ] Nocona wise, LV's will be probably be a bit better than their non LV counterpart.. if the cost is prohibitive, though, go with a better chip with a higher multi :-]

Ah, thanks for all the info perfectturmoil

To clear things up a bit, I'm probably most interested in how the newly released "Irwindale" 3.0ghz, R0 lv's would fare. I've been curious ever since since I saw the 55W rating.

Abercrombie_Boy said:

Ah, thanks for all the info perfectturmoil

To clear things up a bit, I'm probably most interested in how the newly released "Irwindale" 3.0ghz, R0 lv's would fare. I've been curious ever since since I saw the 55W rating.

Click to expand...

Irwindales are just Nocona's with extra cache. So: The overclockability is "good", but you MIGHT fare better with regular xeons. Like I said.. the circumstances are good, due to the low wattage low heat output, BUT your limiting factor will most likely be the motherboard.. I think the top you could ever expect would be maybe 260fsb.. and that's with all of the mods possible on a very high dollar, very no warrantee board ;-] More realistically, you will probably be looking more around the 240 range or maybe even lower.

It's my feeling (and this may be way off) that you will not be able to realize the potential of these chips. Yes, they should be able to clock sky high, but the other problems will likely overtake em. IF they are similarly priced to the non LV chip, definatly go for it - IF you could step up a few models for the same price, I would go with that.

Of course, I could be totally off base too ;- ] Lets see if anyone else has any input...

Hey thanks again for the input! After looking around at the current selection of xeon motherboards, I totally agree. I defintely should be worrying more about the mobo then the cpu!

Why not 2.4Ghz 533fsb lv M0 xeon? cheaper and oc better. you usually get at least 3.2 ghz, DH800 is better choice, although pc-dl is also a good choice, but you need to mod it first.

I have a feeling that's what I'll go with. The cheapest I can find the 3.0 lv's is $500!!