What is the difference between Dell Latitude 3x90, 5x90 and 7x90?

Like in topic, I can't find any detailed information.

 

Without having looked the nomenclature makes me think the sizes are different. 13"/15"/17"

UNless you were inquiring about something specific?

 

Each one is higher end than the last. In the past, that meant the 7xxx line was the top end performance machine, but now it really means it's the slimmest of the three. It does get slightly better display options (in terms of gamut), but it no longer has a performance edge over the lessor models. It has mostly every business option (vPro, smartcard, WWAN).

The 5xxx line now gets the performance chops of the lineup. It has the only remaining dGPU option (a fairly weak, oddly old, and power hungry MX130) and the 5x91 also gets H series CPUs (though it's not generally capable of cooling the U series quad cores, which makes cooling the H series chip a potential exercise in frustration). It inherits the 7xxx line's business options.

The 3xxx line is built without the metal skeleton of the higher end lines. It lacks the dGPU option of the 5xxx line and it doesn't have the smartcard reader. It also lacks the Trackpoint option and is really more like a business version of a consumer laptop (long term support, buying options, etc - one can still option Intel 6th gen chips, for example).

 

Nah, that would have made too much sense... Better keep them guessing, right?

 

I stand corrected lol

 

OP did blank out the sizes with "x", since each 3x90, 5x90, and 7x90 range accounts for multiple sizes and variants. The 5490 got a boosted variant called the 5491, the 7290 has a (previous gen) convertible variant called the 7285, and the ruggedized versions all fall under a somewhat similar naming scheme, though the generations are abstracted even further.

However, the naming scheme (so far) has been (with the partial exclusion of the ruggedized varaints):

(e.g) 7490
7 - series
4 - size class, 14" in this case (14.0" display)
9 - generation (Dell generation)
0 - variant. 0 is usually the standard version, 5 or 9 have been used for various convertibles.

Mine is the E5450, which follows the same schema, but adds an "E" to signify it's from the "E generation" of Latitudes (I had a D630, which is from the older "D generation," and a C840 before that from the even older "C generation"). Dell dropped the prefix with the Latitude xx80 lineup (which also dropped the docking port - called the "E port," presumably for the "E generation" - this is a likely reason why Dell dropped the "E" prefix altogether).

 

Bit of history:

There used be three series of latitudes, based on screen size 4xx (12"), 6xx (14"), and 8xx (15")
Then there were two: 4x00/4x10-series (12-13") and 6x00/6x10 (14-15") -- Dell had a whole 'nother cheaper, Vostro, for the cheaper small business machines.
Then there were two, 5x20 (cheaper models) and 6x20 with the cheaper -- Dell had a whole 'nother cheaper brand, Vostro, for the cheaper small business machines.
Then for the Ivy Bridge machines, Dell started selling three different versions of the E6430 -- the regular one (large-chassis), the slim one (E6430s), and ultrabook (E6430u). This was the last generation of Vostro (which were 3x60s; their 3rd digit followed a different pattern.) The E5x40 were still around, still cheaper.
Then for the Haswell machines, Dell called what would have been the E6440u now the E7440 and the E6240 the E7240 (which also got a lot thinner). The E6440 was roughly the same chassis as the the slim E6430u. The E6540 was the last big-chassis E-series machine. The Latitude 3x40 series was a rename of the Vostro. So other than the two legacy E6xxx models, everything was standardized as it is today.

The one distinction for the Haswell generation is that they had no full-power 14" model anymore, which was especially funny as that was the first generation where Lenovo did (the T440p) - they were pushing the M3800 as their lighter, full(ish) power machine.

The E6xxx branding went away after Haswell, and it's been consistent on the same 3 / 5 / 7 lineup that Intel's been using for about the past 10 years; basically "3 = lower-cost small business models, 5=mainstream models, 7 = premium ultrabooks with more business features than the XPS."

The H-model E5x70 and 5x80 are kind of odd ducks since they're quite a bit more powerful (and run hotter, etc); renaming that to a separate model number in the 5491/5591 makes a lot of sense to me.