1. What memory do you have installed (model number)? (In other words, are you sure it's all 1600 MHz?) 7010 supports both 1333 MHz and 1600 MHz memory, but if one or both is rated 1333 I believe that's the speed it'll choose.

2. I think those are in the Intel chipset driver package; see @speedstep 's response here. Optiplex 7010 drivers are here.

I have tested with G Skill, Crucial, and KIngston RAMs (single module at slots 1, 2, 3, and 4).  They all run at DDR3 1600 on another board.  The board in on a cardboard box with one i7 3770 CPU, one module of DDR3 1600 RAM, one USB mouse, and one USB keyboard.

@NJDave 

@furballi 

You don't get to choose the ram speed. Especially with Optiplex because XMP is not supported.   Ram that is too slow will fail especially if its not low voltage 1.35v/1.5v compatible with 16 gig or 32 gig depending on the cpu.  The reason I choose 1600 ram is that its CAS 9 which is some of the fastest ram for these models.  Corsair Vengeance Pro DDR3 1600 C9   PC3 12800

Corsair CMY16GX3M2A1600C9  B00D2LGRPG

See

https://www.userbenchmark.com/UserRun/51297060

All of these modules meet the DDR3 1600 specs....1.5V at 9-9-9-24 or faster.  I could easily push them another 12% without bumping up voltage. Crucial and Kingston are quality memory manufacturers with very conservative specs.  These modules are properly detected on a Gigabyte and Dell 660 Inspiron boards at the default AUTO mode.

@furballi 

@NJDave 

XMP IS REQUIRED for 1600 Mhz

JEDEC standard, DDR3 speed is

DDR3 800/1066/1333 so, any spec higher than DDR3 1333 uses XMP profile. None of the optiplex models support XMP.

Intel extreme memory profile xmp

On page 13 of the technical guide book, it states 1600 MHz with footnote.

1600MHz memory will only perform as 1600MHz memory when 3rd generation CPUs are used

Something I should mention is KVR, Kingston Value RAM, doesn't always work well in Dell's.  We've seen problems with it in this forum.  This does not mean it never works though.  Seems to be a little bit of hit & miss.  As for Kingston RAM that isn't KVR, haven't seen any problems.

I'm quite sure it's not the memory.  Was hoping someone had hands-on experience with this 7010 board and a 3rd gen Intel i7 3770 CPU.  Dell's data sheet shows DDR3 1600 capable with this CPU.  Perhaps there was an issue with the A29 and I need to downgrade to A28.

That's great.  So these boards are picky when it comes to memory.  I only have G Skill, Kingston, Crucial, and Patriot.  What is the timing as reported by CPUz?  Is the board running at 1T or 2T?