"Negotiated Link Speed" question to make informed decision on upgrading my hard drive

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matthias1981 Author

Level 1

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"Negotiated Link Speed" question to make informed decision on upgrading my hard drive

This is my first post on any help forum I've made in a while as I have usually found answers if I looked hard enough. I am glad I caught and investigated this detail before buying anything that may not improve. What I really want to do is top my macbook out. I'll try to provide as much useful info I can and appreciate what clear insight anyone has for me.

While comparing the specs of my current hard-drive to the SSD ones, I couldn't help but notice these line items:

Link Speed: 3 Gigabit

Negotiated Link Speed: 1.5 Gigabit

While I spent a great deal of time researching similar concerns I could not find the answers that I needed, or made any sense. I'm going to include the hardware specs of my system to make this easier for anyone who is more knowledgeable about what is causing the 1.5 limit. My current stock hard drive is a Seagate Momentus 5400.6 SATA.

Serial-ATA:

NVidia MCP79 AHCI:

Vendor: NVidia

Product: MCP79 AHCI

* Link Speed: 3 Gigabit

* Negotiated Link Speed: 1.5 Gigabit

Description: AHCI Version 1.20 Supported

Hardware Overview:

Model Name: MacBook Pro

Model Identifier: MacBookPro5,4

Processor Name: Intel Core 2 Duo

Processor Speed: 2.53 GHz

Number of Processors: 1

Total Number of Cores: 2

L2 Cache: 3 MB

Memory: 8 GB

Bus Speed: 1.07 GHz

Boot ROM Version: MBP53.00AC.B03

SMC Version (system): 1.49f2

All I am looking to do is top out my system hardware wise. I already maxed the RAM and was interested in getting an SSD. Before I do....I need to know why the 'negotiated link speed' is not reading 3gb as well, and if it's something I can correct. If I upgrade to a 6gb SSL and the value still reads 1.5 I'll have wasted my money. Thanks all.

MacBook Pro, Mac OS X (10.7.2), MacBookPro5,4 2.53ghz

Posted on Oct 23, 2011 8:25 AM

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Answer 1

Best reply

Grant Bennet-Alder

Level 10

127,603 points

Oct 23, 2011 8:43 AM in response to matthias1981

The SATA Links speeds are just specsmanship. What you need to do is a "Bottleneck analysis".

The SATA Hard drives available today have a seek time, about 12 to 20 milliseconds, followed by rotational delay while the platter spins around so that the data are under the read/write heads. That is half a revolution at 7200 RPM (about 4.2 milliseconds) for desktop drives, slower for laptop drives spinning slower.

At the instant the data are available under the read-write heads, today's BEST 7200 RPM drives with perpendicular magnetic regions can source that data off the platters no faster than about 125 MegaBytes/sec, or about 1000 Megabits/sec. 1.5 Gigabits a second SATA transfer rate is still way faster,

The bottleneck is the drive's best-case transfer rate.

The specified Link speed of your MacBook should be published, but unless it is brand new, it will not be faster than 3 Gbits.sec.

Presuming that SSD spec refers to the worst-case bottleneck (which I sincerely doubt) 6Gbits/sec drives appear to be a waste of money, since your MacBook cannot run its SATA Bus that fast.

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Answer 2

matthias1981 Author

Level 1

0 points

Oct 24, 2011 5:09 PM in response to Grant Bennet-Alder

I looked in as many sources as I could find, and didn't see any 'published' link speed for my macbook. I am led to believe that it is 3gb based on the system report. Since my 5400rpm drive cannot physically achieve much less than 1gbs, if what your saying is true (which is sounds to me that you know what you're talking about).

With this understanding, even if a 7200rpm drive can't saturated the 1.5gb, and even if my Macbook data *may* not be able to exceed 3, would it be logical to say that an SSD would gives me 3x the speed if I upgrade? I'm just looking to get the most out of my computer with the current processor and the 8gb of RAM. If it makes the music software, opening/closing programs, reboot, start-up, shutdown and things like that more noticeably 'snappier'. I can be comfortable with the investment.

"The bottleneck is the drive's best-case transfer rate."

I would like to know how to go about determining this. I also need to know if I have to limit my choices to an SSD based on the recommended upgrades for my specific computer:

http://eshop.macsales.com/MyOWC/Upgrades.cfm?&model=353&type=Internal+Drive&sort =pop

or if I can get a discounted one such as this:

http://www.microcenter.com/single_product_results.phtml?product_id=0364781

Speed and compatibility. Before I upgraded to this macbook from my PC, I was chasing incompatibility issues all over the place and got to spend less than 10% of my time actually working on music/video production. If only I had know then what I know now….but that's why I gotta do my homework before buying everything these days

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Answer 3

Oct 24, 2011 5:18 PM in response to matthias1981

OWC/Macsales will have the best track record for compatibility.

They have some tests on their site on this page:

http://eshop.macsales.com/shop/SSD/OWC/Aura_Pro_Express

click on the links part way down that say:

See the performance difference

Read skeptically. Only the straight sequential read come anywhere near what you are hoping for.

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Answer 4

matthias1981 Author

Level 1

0 points

Oct 25, 2011 12:41 AM in response to Grant Bennet-Alder

"Read skeptically."

Correct.

Now my next question is, did a separate entity not otherwise contracted by OWC perform these tests? How could I verify and trust these results are accurate considering the information comes directly from their own website. What arguament would their competition against these results? Does Apple agree? Certainly the competitors products don't all perform the same as each other and "may" value their credibility and increased sales for such.

Hehe, I don't mean to be a critical *******. But I believe in the "buy it once" approach I took when I bought my Mackie studio reference monitors. Which is more subjective given the needs of the audio engineer. I've been duped before.

Thank you, for your advice and prompt responses. More than likely I'll purchase with the OWC ones, I just gotta hear all sides of the issue since everyone claims to be the best these days.

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Answer 5

Oct 25, 2011 9:15 AM in response to matthias1981

They claim those results were obtained by:

http://www.storagereview.com/

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