Intel Core i7 and Core i5 “Lynnfield” CPU Review

Enter Core i5 and Core i7 (8xx)

I’m not going to rant about Intel’s naming scheme here, but I will point out that it may lead to some confusion. The new chips, which sit on a brand new chipset and are completely incompatible with the one before, share the same name as the old ones – Core i7. What you have to do now is look at the model number to know if you need an X58 chipset, or P55. That sounds straightforward to most of our readers, I’m sure, but to many others this is sure to lead to some confusion. Or maybe it won’t, I don’t know. At the very least, Intel can further separate its “Extreme Performance” marketing target from “Performance”, something they’ve wanted to do for a very long time. In the past, nothing was stopping people from using an “Extreme” chip (such as Core 2 Extreme QX9770) on a “Performance” chipset (such as P45) when they were supposed to be using it on an “Extreme” chipset (such as X48). Now, if you want an “Extreme” CPU, you’ll have to go all the way and buy an “Extreme” motherboard.

The Core i7 8xx intends to fill the “Performance” desktop segment, while Core i5 is for “Mainstream”. That means i7 9xx will be for “Extreme Performance”, and I guess the lower end 9xx models will eventually be discontinued completely. There is still some overlap with Core 2 Quad, with the Q9550 costing more than the i5 750. I assume that by the time Core i3 is introduced, that’ll be the last of the esteemed Core 2 series.

There are many aspects to look at when comparing CPUs, so I put together this handy chart. In it, I have listed all the Nehalem chips that are available today:

Model	i5 750	i7 860	i7 870	i7 920	i7 950	i7 975
Family	Lynnfield			Bloomfield		Bloomfield XE
Base Clock (GHz)	2.66	2.80	2.93	2.66	3.06	3.33
Max Turbo	3.20	3.46	3.60	2.80	3.33	3.60
Turbo Power	1/1/4/4	1/1/4/5	2/2/4/5	1/1/1/2	1/1/1/2	1/1/1/2
Uncore (GHz)	2.13	2.40		2.13		2.66
Official Memory Support	2 x DDR3-1333			3 x DDR3-1066
DMI/QPI Speed	DMI 2.5 GT/s			QPI 4.8 GT/s		QPI 6.4 GT/s
Socket Type	Socket H (LGA 1156)			Socket B (LGA 1366)
Cache	L2: 256 KB per core L3: 8 MB Shared
Thermal Design Power	95 W			130 W
Die Size	296 mm²			263 mm²
Transistors	774 Million			731 Million
Hyper-Threading	No	Yes
VT-d	No	Yes
Price (Sept 2009)	$210	$300	$580	$280	$570	$1000

As you can see, there many things to compare, so enjoy gleaning over the chart for a while. The most remarkable improvement for Lynnfield is how Turbo Boost works. Previously with Bloomfield, it would ramp up the multiplier by 1 for any multi-threaded load, and 2 for a single-threaded load. This now varies with Lynnfield chips, with the 8xx series going up by 5x for heavy single-threaded loads. This is a maximum clock speed increase of 666 MHz, while even Bloomfield Extreme would go up by 266 MHz. This means that even single-threaded performance will see a significant increase.

Furthermore, higher threaded loads under 4 cores are still able to ramp up by more than 1x multiplier. For instance, the Core i5 750 will go up by 4x even on a three-core load, whereas previous Nehalems would only go up by 1x on all multi-core loads.

You will also find that all differences between the i5 and i7 are artificially implemented to fill the $200 market segment. In other words, Intel has basically “clipped the wings” of its CPU to sell it at a lower price. The i5 lacks Hyperthreading, which as you know can improve performance in many scenarios. Also, Turbo Mode is less aggressive, and it lacks VT-d (or an input/output memory management unit). If you don’t know what this is, chances are you’ll never have to worry about it once in your life. But I mentioned it anyway, because the people who do care about this kind of thing will point it out. Loudly.

If you needed any hint that Intel plans on discontinuing the lower models of 9xx series, just check out how the prices compare. The i7 860 directly replaces the i7 920, and the i7 870 replaces the 950. After reading this review, you will see that there is literally no reason to choose a 9xx over their similarly priced 8xx cousins, unless you plan to continue upgrading with $1000 CPUs, or really think you need two 16x PCI-E slots for dual graphics (you don’t right now, but you may in the future – we’ll have to wait and see).