Samsung SM951 AHCI write speed reduced

[tsialex]

Hey guys I'm new to the forum but really need help and I think you're the right people to help me. I have a 2010 Mac Pro 5,1 with a 512GB Samsung SM951 which is experiencing reduced performance. From what I'm reading here it looks like I need to boot into single user mode and force trim.

however my problem is that when I try to boot into single user mode (cmd + s) nothing happens. i hear the boot chime but then it just does nothing. I've held cmd+s for up to 10 minutes hoping that maybe it just takes time, but it never does anything and I eventually just have to reboot it. I've experienced the same problem when I was trying to clean install High Sierra and was trying to cmd+opt+R. Nothing happened. I think it would let me boot into cmd+r though, but not the others. Any solutions to this problem? Thank you!

You need a GPU with pre-boot configuration support (aka boot screens), without one you can't enter Single User Mode.

 

[jd.fordyce]

You need a GPU with pre-boot configuration support (aka boot screens), without one you can't enter Single User Mode.

I am using the original Radeon 5770 that my 5,1 came with. It boots up perfectly fine normally. Is that not the kind you're talking about?

I did find this article here:

How to Enable TRIM on Third Party SSDs in Mac OS X with trimforce

For Mac users who utilize third party SSD volumes, the new trimforce command allows OS X to forcibly enable the TRIM function on those drives. trimforce is built directly into newer releases of OS …

osxdaily.com

I followed its instructions and it was successful. Then I ran Disk Speed Test and my write speed is up from 100MB/s before to ~600MB/s which is a huge improvement. (When I first installed it I was getting ~1500MB/s Read and Write. My write speed had fallen down to ~100MB/s but my Read remained at 1500.

Is this good enough or is it not the same thing?

 

[tsialex]

I am using the original Radeon 5770 that my 5,1 came with. It boots up perfectly fine normally. Is that not the kind you're talking about?

I did find this article here:

How to Enable TRIM on Third Party SSDs in Mac OS X with trimforce

For Mac users who utilize third party SSD volumes, the new trimforce command allows OS X to forcibly enable the TRIM function on those drives. trimforce is built directly into newer releases of OS …

osxdaily.com

I followed its instructions and it was successful. Then I ran Disk Speed Test and my write speed is up from 100MB/s before to ~600MB/s which is a huge improvement. (When I first installed it I was getting ~1500MB/s Read and Write. My write speed had fallen down to ~100MB/s but my Read remained at 1500.

Is this good enough or is it not the same thing?

SM951-AHCI TRIM don't work correctly, you will have to do this frequently. Even with this problem, you can improve your speeds if you keep 20~25% free space at all times, this way garbage collection and spread writes algorithms have space to work.

Don't fill up your blade.