Mac Mini only runs 1.5 gigabit on SSD

Thanks @diablote for a really great post! You did some good investigations here. The buggy NVidia SATA chipset has a negotiating problem and your testing shows that is is a timing problem on startup. The chipset does not really care if the drive is 6 Gbps or 3 Gbps but is saying " can I negotiate with you - can you do 3 Gbps?" So on a delayed bootup the SATA chipset has time to negotiate with the disk and does not give up straight away.

The Sandisk firmware is forcing the drive from 6 Gbps to 3 Gbps which maybe the chipset understands then faster. I wonder if you tried my approach with leaving the SSD on power-only for some hours? Since the last upgrade to OS X 10.10 the SSD is still on 3 Gbps on every startup. I have not upgraded to OS X 10.11 but if I decide to do it I will post results.

I came across your USB power-only post and was about to try it when I found the Sandisk firmware addressing the issue (leading to the workaround I described). Given the trouble of opening the dang Mini and how seldom I restart it (it's an always-on file server), I probably won't get around to it soon. However, at some point I plan to replace the dead Superdrive with a SATA drive caddy, and I can test your method then. I then hope to add another SSD Plus and set it up as a RAID 0 with the other one.

Sure let us know if you test the RAID 0 setup. I fear newer SSD drives will be even more incompatible in the future to downgrade to 3 Gbps but then again how long will a Mac Mini 2009 last? Seems these macs last forever. I just fetched my old SE/30 from the loft and booted it up straight away (from 1989!) to play Prince of Persia. Wow, that is a fast mac, really.

I successfully swapped the dead internal Superdrive with a SATA 2.5" HDD caddy and installed a second Sandisk SSD Plus. I striped the two SSDs into a RAID 0 volume and successfully got El Capitan installed on it (a feat in itself thanks to Apple's disastrous gutting of Disk Utility). The link speed issue persisted (and still persists), and the power-only mode you recommended did not fix it. Further testing showed that the link speed is actually just random, and no interaction at startup influences the outcome. Out of 43 startups (21 restarts, 11 startups from off, and 10 startups from off with Startup Manager), I got 25 at 1.5 Gbps and 18 at 3 Gbps (58% and 42%, respectively). The highest number of startups at the same link speed was 4, and the minimum was 1. Interestingly, the second SATA channel always came up at 3 Gbps, though the speed of the volume went as the link speed of the first channel.

Hi @diablote, did you try the trick with an external CD to delay the startup? Would be interesting to see if a delayed negotiation would help.

Sadly, the logic board has an issue which you can't over come with the SSD you are using. You need a fixed SATA II (3.0 Gb/s) SSD unit.

What is happening here is the SATA I/O speed sense logic on the SSD is getting confused. The sensory logic can't reliably tell what the systems SATA port speed is so it jumps down to the slower speed to make sure it will work (your SanDisk z400s 128GB drive). Your other SSD (SanDisk Plus 120Gb) is really not the right drive either for a slightly different reason. Unlike your z400s drive which has the ability to match up with any SATA I/O speed your Plus drive only has SATA III (6 Gb/s) or SATA I (1.5 Gb/s) compatibility mode. If you had a different system with a stable SATA II port the Plus SSD would never run at SATA II unlike your z400s.

Reference: Upgrading old Macs to SSD’s Which explains the problem.

OK what to do? See if SanDisk has a firmware update for your z400s SSD drive to over come the Mini's port problem so its able to run at SATA II correctly. Accept the fact the Plus SSD will only run in compatibility mode (SATA I) or look at upgrading it to a Fixed SATA II drive if you can find one or if you do manage to get the other system to work with the z400s SSD with updated firmware get a second z400s drive. If you can't get the z400s to work you'll need to get different drives or accept the fact you'll only get SATA I performance in this series of Mac Mini.

Reference:

SanDisk SSD Plus specs

SanDisk z400s specs

Your systems specs:

Mac mini 2.26 GHz Core 2 Duo (Early 2009)

Mac mini 2.66 GHz Core 2 Duo (Late 2009)

Now I have results from Blackmagic Disk Speed Test:

Mac mini (Early 2009) with SanDisk SSD Plus - Read/Write=140/100 vs. 520/180 (from specs)

and

Mac mini (Late 2009) with SanDisk z400s - Read/Write=265/150 vs. 540/340 (from specs)

Really, I satisfied with the speed even for Mac mini (Early 2009) in comparison with usual HDD, but from this data I cannot understand, what is a real negotiation speed in SATA? If I understand correctly, the spec's speed presented for 6Gbit/s. So I conclude, my "Late 2009" runs 3Gbit/s. Is it correct?

If you look at the speed disk image I posted you get an idea of 3Gbit/s results which seems like you have now.

So here's the corrected numbers from Mega Byte to Mega bit:

140/100 : 1120/800 basically SATA I (1.5 Gb/s) throughput

265/150 : 2120/1200 basically SATA II (3.0 Gb/s) throughput on the low end.

Did you review this link? How to change the Interface Speed of your HGST Hard Drive from SATA-III (6 Gigabit) to SATA-II (3 Gigabit). It goes into the issue a little bit deeper and they offer an optical drive carrier which supports the faster SATA III drives (HD or SSD).

Also don't get caught up in all of the benchmarks between the drives. Having a Porsche is greate if you can drive it on the Autobahn, doesn't help you drive in downtown Munich :-) Basically, the limits of the system remove most of the gains from a better performing SSD. Focus on what your needs are in the SSD's size and if it can be set to SATA II so it works correctly in your system with the carrier you have or get one that resolves the problem like this one in the link.

Yes i explored all the links, but mine is from 2009, here is 3,0 the maximum.....

It´s clear that all that 6,0 Benches don´t matter much for my case.

I´ve concentrated on the type of Nand memory --->MLC

and explored the Type of Controller --->Silicon Motion SM2246XT

Voila, it seems that these sucsessfull tested in above, the crucial bx100 and the sandisk Plus, they almost have the same Controller!

As an other result i learned that my fine working lowend sandisk ssd 128 could be replaced by a faster sandisk Plus. I look forward :-D

(from technical sight, there were also vram problems in this nvidia chipset generation around 2009, oven-bakening the logic board helped very well ;-)

In my case (mbp mid 09) after the sandisks i was testing a samsung evo 850 250gb(MZ-75E250) since june and it went fine under El Capitan. Now i've upgraded to a 500gb evo in december, works also fine, 3Gbit, trim enabled.

no poblem to be fixed, happy holidays @ all

Interesting if it works. Have to try that. So "some idle time" is 1 minute? 2 minutes or more? Will post back if it works!

I have almost given up getting this to work stable. It is just luck now if I get 3.0 gb/s. The only stable option I can conclude from all the posts is to attach the drive to the CD-ROM cable which seems to run stable at 3.0 gb/s. But then again will have to test. This is museum stuff anyway :-)

Your testing makes sense! As you have a auto sensing SSD (Samsung) what you are seeing it the SSD is dropping to 1.5 Gb/s at boot up and then as the systems port is running clean and is accessing a second partition it adjusts to the 3.0 Gb/s speed. The only risk here is over time the dirty cache writes within the Linux partition will build up and that could cause issues.

Still best to just get a fixed speed SATA II (3.0 Gb/s) SSD like OWC's Mercury Electra 3G

@danj

Thank you for your meaningful comment Dan.

I learned something again :-)