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dubdromic

Member

From: Dallas

Registered: 2010-12-31

Posts: 3

Website

SSD speed issue

Howdy.

The thread title may be misleading. I don't have an issue as much as a non-problem that's driving me nuts. A luxury issue, as it were.

I have an early 2008 MacBook Pro running an 80 gig Intel X25-M G2 SSD. I was perusing the wiki when I came across the SSD Benchmarking page. The first benchmark entry on there is the same drive I have, yet that benchmark is over twice the speed I've seen with the same utility (hdparm -tT). Other benchmarks on the web confirm around 250mb/s is what i should be seeing.

Here's my hdparm -tT output. I also tried the 'dd' version of the benchmark with similar results.

sudo hdparm -tT /dev/sda3 
/dev/sda3:
 Timing cached reads:   3150 MB in  2.00 seconds = 1576.98 MB/sec
 Timing buffered disk reads: 402 MB in  3.01 seconds = 133.60 MB/sec

I know MacBooks disable AHCI without OS X running so I re-enabled that. It was a slight improvement (110mb/s to 130mb/s). Any ideas? The only other things I can think of are alignment issues or SATA I vs SATA II. Everything I can find says that this laptop has SATA II capability, and (unless I'm awful at math) my sector alignment is correct.

Thanks!

pataphysician

Member

Registered: 2010-09-04

Posts: 46

Re: SSD speed issue

If it's an Intel ICH8-M chipset, and you also have a PATA optical drive, then it will only be capable of SATA I Speeds. This Chipset had a problem running at it's full SATA II capabilities if it also had to do SATA-PATA bridge, so in laptops with an optical drives, it is unable to do more than 150MB/sec.

Last edited by pataphysician (2011-01-25 22:52:46)

dubdromic

Member

From: Dallas

Registered: 2010-12-31

Posts: 3

Website

Re: SSD speed issue

Good to know. So...if I remove the PATA drive will it run at full SATA II speed?

pataphysician

Member

Registered: 2010-09-04

Posts: 46

Re: SSD speed issue

I don't think so, I think it's setup in manufacturing of motherboard, to use the SATA-PATA Bridge ability of the SATA chip, and can't be changed.

Intel also made a ICH8-ME (enchanced mobile) that had seperate chips for PATA and SATA, without making the SATA chip do double duty if you needed PATA, these work fine in SATA II.

Apple just made a bad choice on chip set and optical drives, probably because at that time, they personally were only selling SSD's that could not saturate SATA I.

Last edited by pataphysician (2011-01-26 16:37:05)