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Proper RAM for C2D Rig, and OCing?

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December 7, 2006 3:42:29 PM

Hey everyone, I mostly frequent the homebrew area but I thought this is the best question for the RAM enthusaists out there.

I'm building a C2D rig, either with the 6400 or 6300, and wanted to be sure to get the proper memory. I had for some reason assumed that PC2 8500 (1066 mhz) was the proper RAM; the cost alone nearly made me lose my stomach and nearly killed my dreams of a C2D Rig (1 Gig for $200 = insane to me!)

But in a homebrew discussion about my rig, someone posted this ram: OCZ Gold 1GB (2 x 512MB) (PC2 6400)

I was slightly confused, and when I came here, some people were even dicussing about putting C2Ds with even lower than 800 mhz, around 500 or 600!

So, clear the air for me here if anyone minds; whats the best RAM for me to buy if I want a good, affordable, C2D Rig. Will I need to OC the RAM and CPU and such if I want one? And if so, is it just easier to buy more expensive RAM rather than a cooling system? I'm not too savy on the cooling end of things along with OCing so, its a subject i'm lacking in.

Sorry; I know this is probably the fiftith thread today on the subject, but most posters seem to be asking slightly different questions or I don't seem to catch onto the replies very well.

Thanks to anyone who wants to help; much appreciated.
December 7, 2006 3:54:30 PM

To get a decent overclock on a 6300/6400, you don't need 800 RAM, and you don't need an aftermarket CPU HSF. You can hit a good OC with 667 RAM and stock HSF, if you have a decent mobo and RAM.

If you don't want to OC, a 6400 is the better bet for the money, and you can even get 533 RAM. But 667 is pretty much the same price, so just get the cheapest 667 RAM and mobo you can find.


HOWEVER, if you want performance on a budget, check this:
http://forumz.tomshardware.com/hardware/modules.php?nam...

Just get a Gigabyte 965P-S3, 6300 w/stock HSF, and some decent 667 RAM and you should hit 3.0 ghz......which is a 60% overclock! Insane. Then get whatever vid card you want/afford.

Can't beat it if you wanna OC. The C2D chips are begging to be OC'd, so go for it, there's plenty of info and help around here on how to easily get it there.
Related resources
December 7, 2006 4:33:27 PM

Here's the deal with RAM on the C2D:

For any current C2D CPU, the FSB is 266MHz. Memory runs at double data rate (that's the "DDR"), which is 533MHz. So, if you're not going to overclock at all, 533MHz memory is all you need. Any faster RAM, without overclocking, is wasted money.

If you do overclock, you do it by raising the FSB speed. If you buy a E6300, the multiplier is 7, that's where the stock speed of 1.86GHz comes from, 266*7. If you raise the FSB to 333MHz, your CPU goes to 2.33GHz, but your memory will need to be able to run at 667MHz. A 400MHz FSB will get you to 2.8GHz, and your memory will run at 800MHz.

Currently, there's very little use for 1066MHz RAM. You'd need to raise your FSB to a whopping 533MHz, and your cooling needs would be immensely expensive. Also, most RAM will run beyond what it's specified for. A lot of people get 667MHz RAM, but use it up to 800MHz speed. I bought 800MHz RAM, becuase I wanted a pretty high overclock without sacrificing RAM timings.

Good RAM doesn't change the need for CPU cooling - just the opposite. If you get good RAM and overclock, your CPU will get hotter and need better cooling (though the stock cooler does an admirable job up to a point). If you stick with cheap RAM and don't overclock, the stock cooler is fine.
December 9, 2006 3:46:36 PM

I'm looking for some 2x1GB memory. I hope to be able to overclock it to 450 MHz+. Timings aren't much of a concern to me. I'm looking for the cheapest possible RAM that will reach 450 MHz+ does anyone have any recommendations on specifics brands/modules?
December 9, 2006 4:36:35 PM

Err, any DDR2-533 you could 'underclock' to that speed.

If we are talking DDR1, then I'd be looking towards Geil DIMMs personally.
December 9, 2006 4:42:32 PM

Unless we are talking about 450+ FSB (I kind of assume we must be)
December 9, 2006 5:22:40 PM

Overclockers don't make simple terminology mistakes like that.

We make expensive diagnostic isolation errors :lol: 
December 9, 2006 5:36:08 PM

make me feel bad will ya... I meant 450 MHz, as in DDR2 900 equivalent, or 450 FSB.
December 9, 2006 5:58:38 PM

firstly, i would go for the e6300, unless the money is really going spare, and spend the saving on a the best graphics card, the e6300 is still very very fast.

I would reccomend that you use drr2 (As ddr is out of date), 677Mhz, fit all C2D boards and is fast enough to do anything, i person would get at least 2 gigs, and if you dont need to overclock your best option is to go with consair value select twin package, 2X1gb.
December 9, 2006 6:01:43 PM
December 9, 2006 6:23:30 PM

Why is it that you need to install them 1 at a time? Also, are you saying that you just OC one of them until it's where you want and the voltage is set?

Sorry, I'm an OC noob.
December 9, 2006 7:35:33 PM

Any pair of DIMMs that need 2.0+ Volts to work should be installed with 1 x DIMM first, as the PC will cold boot intially at 1.8 Volts.

Then jump into BIOS (don't let OS boot, don't install OS, it may suffer minor corruption), and set VDIMM to 2.0+ Volts (or whatever is called for, might be 2.4 Volts, might be 1.95 Volts).

Save & Exit BIOS / CMOS Utility

Wait until safe, then power off.

Unplug from mains power + unplug mainboard power connection (24 pins).

Install DIMM #2 in the slot specified by the mainboard manual to enable Dual-Channel mode (if available).

Then plug 24 pin ATX back in, close up case and plug back into mains power.

Cold boot PC

The VDIMM will still be at 2.0 Volts (or whatever was specified on the DIMMs and set in BIOS).


The reason is that when installing 2 x high-end DIMMs at once, on the first boot, it'll boot at 1.8 Volts to VDIMM, which might not be enough to power 2 x DIMMs calling for 2.0+ Volts each. However booting with 1 x 2.0+ Volt DIMM the first time with just 1.8 Volts VDIMM tends to work.

It is for this reason that so many people screw overclocks up, and have problems with high performance memory then just RMA it. They never try booting with just ONE DIMM at DEFAULT (which is wrong in this case) VOLTAGE.


Makes sense once you're in the know though, eh ? - :wink:
December 9, 2006 7:45:58 PM

What does cold-boot mean?

Also would this ram be good to get 450+ FSB?
December 9, 2006 8:04:19 PM

So what you are saying is install 1 dimm, fire up the pc, enter bios, set vdimm to factory reccomended voltage, save, shut down, disconnect power, install 2nd dimm, replace power, start back up?
December 9, 2006 8:15:41 PM

Bingo.

PS: Cold-boot means to boot from a true off state. (As in the PC is cold, because it has been off, not warm-(re)booted, etc).
December 9, 2006 8:47:25 PM

THis might seem like a silly question, but is there any real need to have the RAM and CPU FSB at the same clock? Couldn't you get, say DDR2-667 memory, run it on a 5:4 ratio with an E6300? At the moment, for instance, I'm running my opty165 at 305mhz (x9 = 2745) but my ram is at 196mhz (x2 = 392mhz).

So could I just get an E6300 and 2gb of DDR2-667, overclock the CPU to 400 FSB so you get 2.8ghz, and then the RAM will run at 333 x 2 = 667 mhz.

Is this not possible with Core2duo, or is it just a massive performance benefit to have the CPU and RAM running at the same clock speed? As far as I'm aware, the benefits from having memory at a higher bandwith are pretty marginal, so you might as well just get lower clocked memory with good latencies at a lower cost.

Am I just talking crap here?
December 9, 2006 8:54:05 PM

You can, but supposedly it runs better 1:1. I've even heard that running RAM async with the FSB actually decreases performance if you run 5:4 to 667 MHz, and only recovers or becomes profitable at 3:2 -> 800MHz or more.
December 9, 2006 9:06:05 PM

Generally on Intel platforms people try to have peak RAM throughput above what the CPU FSB can 'ask' for.

The reasoning behind it is that the MCH can access the RAM on behalf of the PCI Express Graphics x16 adapter (which might be onboard, and use onboard RAM, so even more important in that case), in addition to the CPU, and SouthBridge, etc.

Take the Q965 and Q963 chipsets for example: http://www.intel.com/products/chipsets/Q965_Q963/index....

You've got a potential 18.5 'competing' for a peak of 12.8 GB/sec.

However the CPU FSB is only half-duplex, and the 8GB/sec for PCI Express x16 is the total of traffic in each direction (worst case scenario), and then a peak of 2 GB/sec for anything under the SouthBridge.

Under real world conditions it would only be using around 75% (or less) of peak RAM throughput, so demand could raise and it would scale well (to a point).

The ironic think is that 'choking' the FSB of the CPU actually 'helps' the design (sharing finite throughput wise), and yet people 'bash' it for having a 'slow' FSB. (of which it gets far better utilility than other solutions, and prefetches heaps of data so it is often ready in, or queued to, L2 cache before actually required).

The Xeon platforms (5100 and 5300) have 2 x 1333 MHz (post QDR) FSBs, for a combined total of 21.33 GB/sec peak, but they can be supplied far more by the chipset via MCH/RAM than the CPUs will use still.

I used to own an Opteron 270 (quad-core, via 2 x dual-cores, at 2.0 GHz, with ccNUMA Reg ECC DDR1-400 - similar to Quad-FX but 2 years before Quad-FX was out), now I run a dual-core Core 2 Duo at 3000/1333 with G.Skill DDR2 @ 667 with moderate timings.

Both platform designs are impressive, but the Core 2 Duo systems have far better price/performance ratios. (and it outperforms my quad-core Opteron at 2.0 GHz, with half the core count clocked at only 3.0 GHz in almost every task).

8) - Tabris:D arkPeace
(I hope that diagram helped).
December 9, 2006 9:18:10 PM

What kind of performance hit are we talking here? Are there any benchmarks for this sort of thing?

One solution, for instance, would just be to get the E6600 and run it at 333 or push it a little until it starts to get unstable. You probably could get 3500mhz or somewhere close. Then you'd have the extra cache as well.

Another way of posing the question would be: Which would perform better: E6600 with DDR2-667, or E6400 with DDR2-800, overclocked to similar levels? They look pretty similar in terms of price.
December 9, 2006 9:19:27 PM

So long as you use the VDIMM procedure above those OCZ DIMMs at 2.1 Volts should work fine.
December 9, 2006 9:27:01 PM

E6600 with DDR2-667 would win out, because the E6400 only has 2 MB of cache vs the E6600 with 4 MB (which makes up for the difference in RAM speed easily).

It is only when the cache hit rate drops too far because something very memory intensive is happening that the cache can't hold that it'll scale 'poorly'.

However the E6600 will still get to 'thrash' the RAM if it wants, as DDR2-667 can provide 10.67 GB/sec, and the 1066 FSB (half duplex) can only use 8.5 GB/sec.

DDR2-800 (12.8 GB/sec peak) to a Core 2 Duo E6400 is overkill anyway. 8)

Same concept, just the delta (RAM to FSB) is less, but the double sized cache and extra clock speed (which hurts cache hit rate if CPU to FSB/RAM delta is big, but not in this cache since L2 cache is 4 MB) make up for it.

Even at DDR1-400 Dual-Channel a 4 MB L2 cache Core 2 Duo would perform well in games, as games tend to cache well and prefetch well.

It really depends exactly what is going on for a given second / minute though - Average numbers don't show the full truth, just a weighted cross section of it - :p 
December 9, 2006 10:26:14 PM

The only reason to get DDR2-800 with the E6400 was to maintain a 1:1 ratio. But it looks to me now like there's no particular reason to. Of course, if you wanted to max out CPU and GFX demands on memory at the same time, faster RAM is going to make a difference, but this would have to be a pretty extreme situation, wouldn't it? Surely it can't make that much real-world difference?

So I guess the overall thought would be: get as much L2 cache as possible, overclock the CPU as far as you can, and don't stress too much about the speed of the memory seeing as there won't be many situations in which it will start to choke.
December 9, 2006 11:04:16 PM

A 1:1 ratio on the E6400 only needs DDR2-533. (Unless FSB overclocking).
- DDR2-800 is 3:2 in the RAMs favour over CPU FSB.
- This can help when PCI Express Graphics devices + South-bridge are trying to get to RAM, which isn't all that often on a E6400 (by comparison).

As I said above, DDR2-800 (PC2-6400) for a E6400 is total overkill. (Waste of money).


I run a E6600 at 3000/1333 (instead of 2400/1066), and yes the 4 MB L2 cache does help at times, as does the +33% higher FSB, and having my DDR2-800 clocked at only DDR2-667 speeds with moderate timings at 2.05 Volts. This setup is failure proof IMHO, Pretty much everyone can do it without opening their case.




Opteron 270 for comparison (4 x 2.0 GHz AMD64 cores).

My TomsHardware 'RSS' overviews page using Live! Spaces.
December 9, 2006 11:17:13 PM

Apparently a 4:5 runs better than 1:1 on 965 chipsets, even with 5-x-x-x timings. These C2D's on 965's LOVE the RAM bandwidth.

Check the benchies, there's plenty on the first 2 pages:
http://forums.anandtech.com/messageview.aspx?catid=28&t...


I'm thinking of going 4:5 myself after doing some reading.......seems like the async doesn't make too much of a difference if you can jack up your RAM.
December 10, 2006 12:13:06 AM

If you're going to overclock wouldn't DDR2 800 be better? The difference in price is only like 15% and you're getting some headroom to overclock. If you use a divider to lower your RAM and up your FSB then you're going to starve your other components of RAM bandwidth when they need it. On every benchmark I've ever seen and on any review I've ever read, they all say that the extra cache really only gives a 3-4% boost in performance. A lot of DDR2 800 modules can even get up to DDR2 1000+ which really gives you some performance to worth with.
December 10, 2006 1:38:47 AM

Well, from benchmarks I've seen, it appears that a 4:5 on a 965 chipset works better overall. 975 chipset is better at 1:1 though.

I haven't tested yet, but the numbers I see show that 4:5 and memory bandwidth is better. I'm not sure about the FSB on it though, I'm really not an OC'ing expert at all. I've got my 6300 and OCZ 800 @ 430x7 = 3.0 ghz @ 4-5-4-15 and runs great. I'm still debating whether I should even bother trying anything else, since this is rock solid stable and is a huge overclock already. I don't need to go for more really, but if there's any way to improve what I have now, or lower temps, etc.......then I'm willing to consider it. But if it's just for a 3% increase in SuperPi then I won't bother because there's no real world point for me.
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