The AJA System Test and DiskTester benchmarks show that the Samsung 840 Pro SSD performs a bit better in the MacBook Pro with TRIM enabled than without it. However, the performance difference is small. Just remember, turning on TRIM isn't just about speed; it's also intended to help reduce write amplification, bolstering endurance.
According to DiskTester, the Samsung SSD in its brand-new state has a sequential read speed (4 KB blocks) of 51.1 MB/s without TRIM, which goes up to 51.5 MB/s with the feature enabled. The results from AJA System Test and the other passes are similar. Conversely, the results also show that the SSD’s performance does profit more from TRIM in a well-used state. This effect is the most pronounced in AJA System Test’s sequential read benchmark, where the data transfer rate increases from 466.7 MB/s to 512.1 MB/s when TRIM is enabled.
AJA System Test


DiskTester


Ah, Apple. Why must it be a love-hate relationship? Clearly, you make some awesome hardware but your pricing and closed-mindedness is @$$munch. You disable TRIM if one doesn't pay 50 to 75% more for one of your lower-performing (than the typical aftermarket piece) OEM SSDs. Shame on you. Greedy bastards. Get with it or continue to decline. It's good to see in the case of TRIM Apple's @$$munchiness is so mindlessly circumvented. ...and to think I once gave them a bunch of my money. 4" Apple...4"
I installed Windows directly, then performed some magic to install bootcamp drivers later, but the problem was that the EFI in Apple PCs disable AHCI when running Windows.
Now Intel'ss SSD toolbox can still perform TRIM even when it's IDE mode (apparently) but i wasn't sure, so i had to Google a solution.
Currently i have to enter four console commands in a GRUB menu before i can boot into Windows over AHCI, and BootCamp doesn't like it when i do.
It's annoying, because i don't know much Linux, and i have no idea how to enable the GRUM menu or some sort of automated boot script that enters those commands for me.
Commands:
setpci -d 8086:2828 90.b=40
set root=(hd0,1)
chainloader +1
boot
Look at crisso2faces comments above - I see that all the time on drives from multiple manufacturers, not just Samsung. Is seeing a couple extra MB/s in a benchmark worth gambling with possible catastrophic failure because you aren't using the system as designed?
If you bought a Mac without doing research into your own required features, return it. If you're past your 15 days, look at it as a lesson learned. Macs aren't for everyone. Realistically, Macs aren't for anyone aside from people who want the most watered down experience possible, but the pro apps keep people in line for computers that don't really fit their needs.
SSDs attached via PCIe, USB 3.0, FireWire, or Thunderbolt cannot receive the TRIM command. Macs won't even recognize them as SSDs nor would the Mac send them the TRIM command even if it is enabled.
The newest MacBooks now use PCIe SSDs.
SSDs (such as OWC Mercury SSDs with SandForce controllers) have evolved to the point they don't need TRIM - particularly when the SSDs are not attached via SATA? They do their own garbage-collection and optimization.
OWC - in particular - advises against enabling TRIM on their Sandforce controller OWC Mercury SSDs since this increases wear and tear on their SSDs. TRIM adds extra unnecessary writes when the SSD already did this on its own. Enabling TRIM would essentially harm the SSD and shorten its lifespan. http://blog.macsales.com/11051-to-trim-or-not-to-trim-owc-has-the-answer
If modern SSDs need TRIM, they would be in danger of serious performance problems if the SSD was attached via a non-SATA connection such as USB 3.0 or PCIe or Firewire or Thunderbolt. Unless the manufacturer insures their SSD's controller does its own version of TRIM, then they would suffer serious performance problems when attached via non-SATA connection compared to the competition.
This is why I argue that TRIM is currently useless in modern SSDs.