Core 2 Duo : Indian Perspective
Hey guys
I have seen a lot of speculation going on regarding what parts everyone is going to get to jump onto the "C2D" (Core 2 Duo) bandwagon. Many are undecided about which processor to get, many undecided about what RAM will benefit them most. And the biggest question of all, how much mullah to blow into buying a Motherboard.
I will try my best to put some of these perspectives to rest to make the job a bit easier for others.
Source and Credits
Apun ka research bhai logon
Was prepping myself for my Conroe plans. Just decided to write this down because I thought this might be of some help to others. Thats it.....Prologue
In 3 hours time I will be making my shift to Bangalore (I hate the new name
) So this is like my last article from Orissa For the time being atleast. I dont know how soon I will get access to the internet again, so I request everyone to kindly forgive any mistakes in the article and to get it corrected via the Mods.... as I wont be able to see the feedback. Hmmph, reps welcome 
[break=Efff Esss Beee]
FSB : "Front Side Bus"
We all know by this time that current Intel processors lack a IMC (Integrated Memory Controller.) While it puts a server limitation on Intel (added latencies, having to communicate over a 'constrained bus' to access memory), it also helps Intel in making radical changes to their architechture without having to redo their memory controller design everytime. FYI, a major portion of the A64 and now AM2 die goes into the implementation of the IMC, which is available to Intel to use for other stuff like gigantic L2 caches.
So now coming back to topic, what is the FSB thing? Basically its a bus over which the CPU accesses the rest of the system resources, MOST prominently the RAM. Since the memory controller resides on the North Bridge (for example, i9xx, RD600, 8xx series, etc, etc and now the brand new NB, 965XX.) Lets do a little math:
Say we have a FSB speed of 533 Mhz (taking for example the cheapest Dual core CPU available now, the Intel Pentium 805D.) Currently, the FSB is Quad Pumped. Meaning the actual bus speed is 133 Mhz, but it is quad pumped (multiplied by 4 by a clock generator) to serve as the system wide FSB.
Now the FSB is 8 bits wide (bidirectional?.) So that gives the total FSB bandwidth to be:
Bandwidth (BW1) = 533 x 8 = 4264 MBps theoritical MAX bandwidth
This implies that the FSB is capable of transferring a max of BW1 to the CPU from the Northbridge per second.
Now lets see how that applies to RAM.
Considering a single stick of DDR2-533 1GB Ram (running 1:2 FSB : DRAM)
The stick is 64 bits wide. Thats 64/8 = 8 bytes wide.
With a signalling frequency of 533Mhz (Double Data Rate, so effectively 2 x 266 Mhz) we have a theoritical MAX bandwidth capacity of:
Bandwidth (BW2) = 533 x 8 = 4264 MBps (same as BW1 from above)
So we see that single channel DDR2-533 is more than capable of saturating the FSB. So contrary to popular belief, putting another stick of matched would do zilch to your bandwidth.
Now this is with your FSB : DRAM at 1:2. Whats the use of the higher multipliers you ask?
Well, raising your clocks greater > DDR2-533 will do zilch for your bandwidth alo. Simply because the FSB is limiting you. However, IF YOU ARE ABLE TO USE A 4:5 multiplier and MAINTAIN THE SAME RAM TIMINGS, what you are effectively doing is cutting down the LATENCY while maintaining the Bandwidth at 100%, which is a win-win situation.
If we wanted to use Dual channel, a 1066 Mhz FSB would easily be saturated because the FSB bandwidth would exactly match the bandwidth of the 2 DDR2 RAM sticks.
So unless you up the FSB to match the DRAM speed, you are not gaining anything other than increasing latencies like mad because of the need to relax them to go to higher frequencies.
So unless you are trying to just test out your RAM, stick to 1:1 or at max 4:5 and tighten the timings as much as possible. That will give max performance.
[break=The price of multis....]
The price of multipliers
Now everybody here doesnt have $500 to spare to get that 10x multiplier and a slightly higher binned chip. Ofcourse it would make things so much easier, but hey, thats not what OCing is about....
Ok, so we settle for a E6600 (2.4 Ghz, 1066 FSB, 9x multiplier, locked upwards) because thats the next best to a E6700. The 9x multipliers demands that we clock the FSB that much higher just to reach similar clock speed compared to a E6700.
But in the retrospect, we can see that this is a blessing in disguise. The general AIR overclocks which people are getting on B0 revision E6600 ES are around 3.4Ghz - 3.7Ghz. If those results are any indicator of the things to come from the later revision retail parts, more people are going to require a FSB in the range: 370 Mhz - 412 Mhz.
Most motherboards (except for maybe the lowest end ones) should easily reach those speeds with minimal boosts to the voltages applied to the chipset.
Those FSB ranges (using FSB : DRAM = 1:1 or 4:5) gives DDR2 speeds of DDR2-740 - DDR2-824 (1:1) or DDR2-925 - DDR2-1030 (4:4)
So the choices in the range are immense. We can get good ram modules for cheap which do tight timings (4-3-3-x, 4-4-4-x, 3-3-3-x, etc.) for doing 1:1 with the FSB (remember, 1:1 implies you use dual channel and use the FSB bandwidth to the fullest) or spend a little extra (sometimes a lot more
extra) and buy ram which will give similar tight timings at those 4:5 DDR2 speeds. It all depends on the budget.Also, 1:1 is going to get more of a limelight once ATI gets the RD600 out in full swing, because of its support of 1T timings (something which has been missing in all Intel chipsets uptil now, atleast the DDR2 ones.) Also, with asynchronous FSB and memory clocks, the need to take the FSB insanely high just to NOT make it a bottle neck for the memory subsystem will become superfluous.
[break=Conclusion]
Conclusion
I have come to the conclusion that, if you are on a limited budget and want to get the best out of your system (with air ofcourse, water/phase etc are not exactly in the buying plans of a budget conscious user), it would be best to stick to:
1) Intel Core 2 Duo E6600 ($300) (try to get the later revisions, as they seemingly clock higher + run cooler, ex C1 and B0, avoid A0 as they didnt clock so well)
2) 2GB of Decent quality DDR2 which does 800-900Mhz at 4-4-4-x or 4-3-3-x or even better 3-3-3-x without the need for extreme voltages (i.e. < 2.3V)
Ex: Gskill 2GBHZ (0605 revisions, 0604 are not bad either)
3) Motherboard which has the enough slots to support your needs and features you demand (like number of SATA2 ports, USB I/Os, PCI-e slots, etc, etc.) Capable of doing 370-430 Mhz FSB easily. Lots of twearking options w/o requiring extensive mods. (ASUS P5B, P5B Delux, DFI Infinity, etc, etc.) Vcore desired = 1.5-1.6V, Vddr desired = upto 2.3-2.4V (to squeeze the last bit out of those timings, particularly with Micron D9s)
With money invested properly in these three (+ a good DX10 capable GFX card) you are all set till Quad Core comes out of labs and becomes mainstream.
Rememeber its your cash, make best of it.....
Regards,
Karan
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