Going to partially answer my own question, in case anyone finds this via google.  It looks like a B&M connector is really a B *or* M connector and should fit either slot.  So it doesn't matter whether the laptop requires a B style connector or an M style connector, because a B&M will work with both.  It would be nice if someone added this to the wikipedia page.  Took me forever to find enough other forum posts to feel confident in this.

But I'm still not sure about length.  2280 vs 2260.  Alienware17 R4 Setup and Specifications  says:

• Two full-size M.2 PCIe/SATA drives
• One half-size M.2 PCIe/SATA drive

I'm assuming full-size means 2280.  But on a different site they have an actual R4 in their hands and are pointing out the hardware.  Inside Alienware 17 R4 – disassembly, internal photos and upgrade options  says

The motherboard holds three M.2 PCIe NVMe-enabled SSD slots with one in our unit taken by a Toshiba M.2 PCIe NVMe SSD with 256GB capacity while the 2.5-inch HDD slot is taken by an HGST drive with 1TB capacity. The other two M.2 SSD slots are also PCIe NVMe-enabled but one of them is 2260 while the other supports the standard 2280 sizes.

My *assumption* would be that the half-size drive is used with the standard sata, so if you ordered one of the ssd+sata versions it would raid 0 the normal 2.5 inch sata drive with the half-size ssd, so it looked like one drive with the os on the ssd for fast boots.  And the second and third drives would be for two full-size 2280 ssd.  But that's not the way the picture looks or their text reads.  Personally, I think their text could be clearer and I trust the pictures.

Just want to confirm before I spend a bunch of money on ssd drives.

Thanks!

Hi jd142‌,

This SSD has not been validated so unfortunately we cannot confirm functionality. You could also try posting this on the Notebook Review and Alienware Arena and see if maybe other users have already tested this SSD.

Just in case thee following table shows the hard-drive options available in this computer.

jd142 wrote:

Personally, I think their text could be clearer 

 

You mean like stating it supports SATA and PCIe Interfaces on the M.2-Slot at the same time. Yeah, right. 

While it's likely PCIe/NVMe, I suggest you wait for machine and buy another that matches its existing SSD's specs.

Let us know what you find and what works. 

Ok, found a good video ( New Alienware 17 R4: Upgrade/Replace M.2 Solid State Drive - YouTube ) that walks through and I was able to get a look.  Plus the laptop arrived and I could look at it as well.  I figured since there were 2 of the full socket open, I'd be fine with that.

- One 2280 socket is taken up by an hgst.com 1 TB 7200 rpm sata.  Replaced with a crucial 2TB ssd, Crucial MX300 2TB SATA 2.5 Inch Internal Solid State Drive - CT2050MX300SSD1 

- One 2280 socket was open.  I put in a Crucial 1 TB stick,Crucial MX300 1TB M.2 (2280) Internal Solid State Drive (CT1050MX300SSD4) 

- One 2260 socket was open.  Nothing yet.  In 2 years I'll probably be able to get a 5 TB stick for have the price of the 1 TB.

Thank you for the info!  This is my first time into the mini SSD size hard drives and I was curious too to for these specs.   The manual could do so much better in letting us know the SSD types that go in.

I've got dual 960evos in raid0 and love 'em as well.

Exactly - I couldn't find confirmation either so I just bought em and hoped for the best.  It's not like they're that expensive, so easy gamble.  I configured mine without an SSD knowing "aftermarket" ones would cost less than half, but my 17r4 ran like CRAP with a spindle drive only.  I almost returned it, it was that bad.  Slower than my 2014 17x - but I (correctly) guessed is was because no SSD....  

I love this thing now, it's a beast.

compugeek5150 wrote:

I've got dual 960evos in raid0 and love 'em as well.

Thanks for the confirmation.

I was 99% sure they should work ... like why wouldn't they? 

oh, if anyone finds a half length nvme, I'm really interested!  I couldn't find one on amazon, but honestly I haven't had time to dig.