I am curious as well about the ability to upgrade the CPU. I have the i7 version of the E6420 and would love to be able to switch to a quad core i7 as as opposed to the dual core that I currently have. I am also curious on whether I can go beyond 8GB of RAM...

I'm running one 8 gig plus one 4 gig stick with no issues.

Note: A21 BIOS

As best as I can tell, the spec sheet limits the RAM to 8GB but, I believe I read somewhere else that it can be upgraded to 16GB. A guy on this thread says he has an 8GB and a 4GB (asymmetrical) dual channel memory configuration on his E6420 so, I'm thinking it may be worth the risk, if you believe you will need that much ram. I don't believe serious gamers need that much RAM on their laptop and, this is no gaming rig. Video editing can use a bunch of ram but, again, that tends to be a very graphics heavy process, which this laptop is not an ideal platform for editing on. For most everyday uses, 8GB of RAM is plenty. Also, considering the price spike, I would not look to upgrade the CPU beyond the i7 2630QM quad core. Plenty of mobile power and, a more affordable price range (currently sub $180 on both eBay and Amazon websites for new / like new, and used very good.)

I'm not so sure about Intel memory controllers versus AMD's, (I'm more familiar with AMD's) but, I don't think there is any benefit to buying DDR3-12800 ram, beyond a small higher potential resale value, since the laptop's are only rated for the DDR-10600; the extra speed is just wasted. You can use the DDR-12800, since it is backward compatible with slower speed limitations of older controllers, you just won’t get the full potential out of them.

I have recently come to own one of these laptops (factory refurbished) and, in looking for affordable performance upgrades, I had the same question about getting a good, workable, i7 CPU upgrade, (mine came with the i5 2520m CPU installed.) Unfortunately, I was not able to find anything on the motherboard from the Dell website beyond their own part number for the MB. I went to the CPU upgrade site, (www.cpu-upgrade.com/.../NC9BU-HM67.html), and, it appears that there are only a limited number of MB manufacturers for the Sandy Bridge version socket G2 motherboards. Basing my compatibility search on the oldest motherboards compatibility chart, I came up with the best quad core for the money being the i7 2630QM. (You can find a few of them now on eBay for under $80.00, "buy it now," with free shipping. And, they are selling like new / very good condition on Amazon for under $150.)

http://www.cpubenchmark.net/cpu.php?cpu=Intel+Core+i7-2630QM+%40+2.00GHz&id=873

The socket compatibility for the i7 2760QM doesn't seem to match the 2011 motherboard's PGA988B socket type either. It may well also be a socket G2 "compatible" but, the PassMark website reports the socket to be BGA1023 rather than the PGA988B. (I believe this is a difference in revision for the MB's chipset, with the BGA1023 being intended for the Ivory Bridge CPU types and the PGA988B being intended for the Sandy Bridge CPU types; the Sandy Bridge CPU's being 2nd gen.) The newer CPU's are most likely not compatible with the Latitude E6420’s older chipset.

I looked up on passmark's website and I found that the i7 2630QM and the i7 3610QM both have the same socket type as the i5 2520M that comes in my laptop.  Has anyone installed or does anyone know if the i7 3610QM will work in a e6420 xfr?

Thank you

I may have posted to soon.

After doing a system test on the dell websitethe computer is now messing up.

I am getting distortion all across the screen.

Horizontal lines, flashing, static(white noise, visual), then the computer restarts or shuts down.

I do not know if this is in relation to the cpu or if the test blew out the video card.

I will swap the i5 chip back in and see if the problem is still there.