What is causing my Mid 2009 macbook pro 5,3 with OS X 10.6.8 having SATA negotiated link speed of 1.5 GB/s on the stock Optical drive and MCP79 AHCI Hitachi with real link speeds of 3 GB/s?

My Mid 2009 Macbook pro 5,3 with OS X 10.6.8 is having a SATA negotiated link speed of 1.5 GB/s on the stock MCP79 AHCI Hitachi.

The actual link speed of the MCP79 AHCI Hitachi is shown to be 3 GB/s on System Profiler. Here is a copy / paste:

Model Name: MacBook Pro

Model Identifier: MacBookPro5,3

Processor Name: Intel Core 2 Duo

Processor Speed: 2.8 GHz

Number Of Processors: 1

Total Number Of Cores: 2

L2 Cache: 6 MB

Memory: 8 GB

Bus Speed: 1.07 GHz

Boot ROM Version: MBP53.00AC.B03

SMC Version (system): 1.48f2

Vendor: NVidia

Product: MCP79 AHCI

Link Speed: 3 Gigabit

Negotiated Link Speed: 1.5 Gigabit

Description: AHCI Version 1.20 Supported

Hitachi HTS545050B9SA02:

Capacity: 500.11 GB (500,107,862,016 bytes)

Model: Hitachi HTS545050B9SA02

Revision: PB4AC60Q

Serial Number: 090519PBC400Q7GR67AA

Native Command Queuing: Yes

Queue Depth: 32

Removable Media: No

Detachable Drive: No

BSD Name: disk0

Rotational Rate: 5400

Medium Type: Rotational

Partition Map Type: GPT (GUID Partition Table)

S.M.A.R.T. status: Verified

Volumes:

Capacity: 209.7 MB (209,715,200 bytes)

Writable: Yes

BSD Name: disk0s1

keymark:-:-:-\:

Capacity: 499.76 GB (499,763,888,128 bytes)

Available: 264.14 GB (264,141,840,384 bytes)

Writable: Yes

File System: Journaled HFS+

BSD Name: disk0s2

MATSHITADVD-R UJ-868:

Model: MATSHITADVD-R UJ-868

Revision: KB19

Serial Number: dE17CD77

Native Command Queuing: No

Detachable Drive: No

Power Off: Yes

Async Notification: No

Mount Point: /

This system doesn't contain any supported hardware RAID devices. If you installed hardware RAID devices, make sure you installed them properly.

I've been searching for an answer, and can not find any.

I believe the firmware version of MBP53.00AC.B03 (EFI 1.7) has been installed for years, and I just noticed this issue. Would downgrading the firmware to EFI 1.6 solve the issue?

The most similar question that I could find answers to seemed to conclude that there was no solution, but that using the EFI 1.6 driver might help speed the computer up. See this link:

How many GB/s is the optical drive bay for a Mid 2009 Macbook Pro(5,4)?