Conroe vs Santa Rosa?

Hi everyone,

I realize that the new Asus C90 has been the hot topic on these boards recently, and that probably all avenues of specs and comparison have been exhausted, but I was wondering if I could start a completely CPU-oriented thread considering the pros and cons of the Conroe processors (quite rare in notebooks) available in the C90, as opposed to the more standard Santa Rosa processors in most other high-end notebooks.

As far as I'm aware, the two processors are quite similar in architecture, and the only thing immediately apparent to me, in terms of performance, is the difference in FSB frequency (Conroe at 1066 MHz, Santa Rosa at 800). The L2 cache size, which is probably the most important aspect of a processor these days is the same at 4MB.

Since we are talking about notebooks, power consumption is an important consideration. If we choose two equally clocked CPUs (the E6600 and T7700) at 2.4 GHz, the power consumptions are 65W and 24W, respectively. However, with Intel Enhanced Halt State technology on the E6600 chip reducing power to 12W during "halt state", the Conroe seems to be very competitive in terms of power.

Now, all I have been doing is comparing numbers. However, there must be some other performance consideration to make, since there is obviously an architectural difference that leads to this dramatic 65W to 24W difference for equally clocked chips. Can anyone tell me exactly what technology Intel is using to save this much power, and what impact it has on the chip performance?

Thanks, and please don't make any comments on why a user called "AMDAthlon" is posting about Intel chips - this account was created 2 years ago when AMD was leading the chip wars.

 

Yea there must be huge differences in the microchip architecture.

the conroe is designed for desktops so it can perform at higher power consumption/heat capacities, but the Santa Rosa chip must fit within a specific heat envelope, power consumtion, etc... which forces the engineers to design a new integrated circuits that do the same that the conroe does but at a lower power consumption, and because of that it costs more.

The C90 uses the Conroe mainly to reduse it's price, it supports some notebook cpu's I believe, but it's mobo auto-oc's Conroe's ^.^

 

So are you saying that there is little or no performance lost by the Santa Rosa due to power issues, and that the only sacrifice made is price?

 

i'm no expert but i'll start my 2 cents by clarifying the apples and the oranges.

conroe is the desktop core 2 duo chip. as you have said, it is supported by the chipsets on compatible motherboards with a fsb of 1066 mhz.

merom is the mobile core 2 duo chip (i think that's still the latest chip). santa rosa is the latest chipset to support this processor and one of it's big features is a fsb of 800.

you are correct, the architecture of these chips is identical - they are core 2 duo processors. in terms of performance, yes the higher fsb is going to improve performance by providing increased bandwidth between the ram and the processor. however, if the ram is not fast enough, it becomes the bottleneck and not the fsb. this is why ddr2 800 is more or less standard on desktop systems now, with people into overclocking going alot higher. the penalty of all this performance in increased power consumption. faster ram, faster fsb = more heat output and more power consumed.

the difference in tdp has to do with voltages. i'm not certain about this so someone else straighten me out please, but i think the mobile chips run at much lower voltages. basically, the mobile chips are binned much higher and so can perform at high clock speeds with less voltage than the deskop units. this is reflected in the price - E6600 is about $300, the T7700 is almost 2.5 times the price.

the "halt" state is exactly that - the processor is halted and not doing anything (this is when your computer is in sleep mode). so no, it's not competitive with the mobile chips in power consumption at all

the l2 cache is also not the most important aspect of a chip, imo. most important is the product of clock speed and operations per clock. second most important is the entire supporting infrastructure of ram, buses, etc, that provide keep the cpu fed so that wasted clock cycles are kept to a minimum. the whole northbridge/fsb approach is not as efficient as the hypertransport bus used by AMD, which is why having bigger l2 cache on an intel chip is indeed an important aspect to obtaining good performance.

so, pros and cons.

the conroe in a laptop gives you faster ram, faster fsb, and higher clock speed for less money. all in all, more bang for your buck.

it also sucks back way more power than a mobile chip and produces a boatload of heat. in a portable case this means high speed fans (and thus lots of noise) to keep things cool. it also means that the conroe will pretty much always need to be plugged in. expect battery life measured in minutes (especially with a powerful graphics card).

 

Thanks for the reply, Dan. You may not think that you are an expert, but you have addressed all of the questions raised in my mind. The low price of the C90, as well as the three massive fans on the back pretty much confirms everything that you said.

Being a Physics major and not an EE major in University, I only have a very theoretical knowledge of electricity. However, I can say that TDP in a CPU is almost exclusively dependent upon the internal resistivity of the CPU, which as you correctly stated is taken into account by the voltage. In very simple terms, V=IR (voltage = current X resistivity). So I think you are safe in your assumption that high TDP is a cause of high voltage.

 

Lets not forget that the desktop chip has about 775 pins, and the laptop chips 478-479. Something else is different about these chips. Higher bandwidths somewhere, FSB increases (we already know about that), etc.

Just because it is the same architecture does not mean they are the same chip but just clocked differently with different voltages. Same architecture means the same legos are being used, but one has more legos than the other.

 

look at the NBR wPrime Hall of Fame for the differences

Of course the desktop CPU's will outperform the mobiles... but the heat and powerconsumptions are factors that need to be thought about.

 

one thing to take into consideration is that the conroes in the c90 are supposedly slightly underpowered from what i remember, so you won't be able to utilize its full power.

 

I was wondering about that - suspected just a voltage change would be a bit of a stretch to knock off 41W of TDP.

So, same Core 2 architecture, same 65nm process, different physical layout? That's quite something to achieve such a reduction in power just by rearranging how the chip is laid out. If that's the case though, I don't understand how it can cause such an increase in price, because if it didn't than the conroe desktop processors would be done like that and have a TDP of 24W also. Guess maybe just lower yields with the merom chips.

 

The c90 is really targeted as a full desktop replacement.

 

I think the c90 sits between super powerfull notebook and desktop replacement, it can do both.

The bigger versions of the C90 the 17" version and possibly a 20" verrsion will definitly be more like desktop replacments.

The big diffrence between desktop and moble cpus is the heat and power of course, but clock for clock the desktop version has more processing power. So a 2.2ghz C2D and a 2.2Ghz Santa Rosa will not be the same. Now in the case of the C90 it has the ability to overclock the C2D to just shy of 3ghz... Now you have a very large lead and even more reason to have one.

The top mobile cpu is 2.4ghz and very expensive, so if you need power the C90 is your cheapest and best way to get it on a notebook.