Thinkpad x201 RAM upgrade

[Coup27]

Very surprised it turned out to be that, but glad it's sorted now.

 

[Thunderbird]

I wanted to add to this in case it helps someone else. Lower density chips helped me too.

I wanted to bring my Lenovo X201 (i7-m620, mfg'd June 2010) from 4GB to 8GB to reduce use of disc caching. Crucial's website said that DDR3L-1600 would work. I couldn't wait for delivery so I bought a Kingston HyperX DDR3L-1600 4GB DIMM (Part# HX316LS9IB/4, UPC 740617233339) from Microcenter. It wouldn't boot when using it alone or in combination with the 4GB already installed.

I returned it and bought Corsair Mac Memory DDR3-1066 4GB from Fry's (Part# CMSA4GX3M1A1066C7, UPC #843591013840). I was unsure about compatibility of Mac Memory, but they were out of the ValueSelect DIMMs. The good news is it worked.

While I understand that faster chips would run at slower speeds, a key difference appeared to be that the Kingston DIMM had 4 chips per side and 8 total, while the Corsair had 8 chips per side and 16 total. The number of chips on the Corsair matched the DIMM that was already installed. The Corsair memory that worked for me is also not dual-voltage DDR3L, but the DDR3L DIMM worked for Essence.

Maybe Lenovo is intolerant of off-spec RAM, but good luck. This RAM is getting harder to find as these laptops get older.