Serial ATA is the evolutionary replacement for standard or parallel ATA. Parallel ATA has been the standard for desktop computing for nearly 15 years. The ATA100/133 standard has begun to run into limitations that reduce its scalability past its current performance. That is where Serial ATA comes in. Serial ATA uses a high speed serial interface to transmit data instead of a parallel interface. Serial interfaces transmit data one bit at a time while parallel interface transmit multiple bits at a time. At one time parallel interfaces were faster than serial interfaces, but with the dramatic increase in speed that semiconductors have had during the past 10 years serial interfaces now offer faster connections with a higher degree of data integrity. Examples of serial interfaces now being implemented are AMD's Hypertransport protocol which is used for interconnetion of motherboard components and in the case of AMD's Opteron, CPU to CPU communication, VIA's V-Link architecture, Intel's Hub architecture, PCI Express, the replacement for today's parallel PCI bus, Firewire (IEEE-1394), Rambus RDRAM, and others.

Serial ATA brings some great improvements to the PC that all users will benefit from. First, the large, limited length ribbon cables have been eliminated. The were a constant hassle to route through cases and impede airflow, which is very important with today's hardware producing so much heat. Now instead of being limited to about 18 inches, SATA cables can be as long as 1 meter.

Second, the peak transfer rate has been increased to 150 MB/s. This is due to be scaled up to 300 MB/s in the Second Generation and 600 MB/s in the Third Generation.

Third, SATA has hotswap capability. This is important to SATA if it is to be integrated into the enterprise market. It accomplishes this by having the new cable design and a new power connector. The first SATA drives should still include the old 4 pin molex connetor until power supplies support the new 15 pin power connector that SATA drives use.

The last important feature that aids in increased performance is Tagged Command Queueing or TCQ. This enables the drives to read data off hard disks in an order that will keep performance from dropping with multiple applications accessing the disk at once. See the picture below:

TCQ Illustration

Features:

• 2 Independent Serial ATA Channels.
• Software RAID 0 or 1 support.
• Low-profile design for use in rackmount systems.
• 33/66 MHz operation
• PCI 2.2 Compliant

Installation and Performance:

The card came out of the box with the low-profile backplane attached, that was changed to the included full size back plane. Install ation was a snap, just put it in the slot and screwed it in. I did run into one problem in regards to the card interferring with SCSI Adapters. I had to change the PCI slot that the card was in because if I had the card in a slot more towards the AGP slot the SATA BIOS would load and not load the SCSI BIOS. When put in a slot farther away from the AGP slot than the SCSI Adapter the SCSI BIOS was loaded first and then loaded the SATA BIOS. This will need to be kept in mind if you use SCSI or ATA controllers that use their own BIOS.

Unfortunately I had no native SATA drives such as the Western Digital Raptor, or the Seagate Barracuda. So, I used the Abit Serillelo SATA to PATA Adapter and a Maxtor D740X-6L 7200 rpm ATA133 HDD. The Adapter appears to have a neglibile effect on performance and it still enables you to take advantage of the SATA cabling while not replacing all of your current ATA100/133 hard drives. An important note, SATA Adpaters only support 1 drive per channel unlike PATA. This is not necessarily a bad thing since PATA drives can only access one drive at a time per channel. This ensures that all drives run independently, getting maximum throughput for each drive.

Adapter in case


SATA to PATA Adapter and SATA Cable


All connected. - Click for larger view.
Compatibility

With Windows XP SP1 there were no compatibility issues. I installed the adapter in an existing system and I did a clean install of Windows XP using the adapter. In both cases I was simply prompted for the driver disk and I was on my way.

Linux on the other hand was a different story. There is driver support for the Si 3112 chip in the 2.4.21-rc1 kernel and in the -ac kernels since 2.4.20. In my test the card would not work properly with the drive. UDMA modes could not be enabled and I would have transfer rates of about 2.6 MB/s. If I forced UDMA to enable the system would hard lock. I tried the adapter in Linux with 2 different Maxtor HDDs, 1 Seagate HDD, and 2 different SATA -> PATA Adapters. This being known I think that the issue is with the Linux driver. There have been people that have had success with drives working properly but I was not so lucky.

Test System:

• Tyan Tiger MP S2460 Dual Socket A
• AMD 762MP Northbridge, AMD 766 Southbridge
• 2x AMD Athlon MP 1900+
• 2X 512MB PC2100 ECC Registerd DDR CL2.5 Corsair
• 1X Maxtor D740X-6L 40GB ATA100 7200RPM hard drives with SATA -> PATA Adatper
• VisionTek GeForce4 Ti4600
• Thermaltake 420 watt ATX 2.03 compliant PSU
• ioMagic 40x12x48 CD-RW
• Realtek 8139 LAN card
• WindowsXP Professional SP1
• Silicon Image 3112 SATA Adapter
• Abit Serillelo PATA -> SATA Adapter
• HDTach 2.61
• SiSoft Sandra 2003
• PCMark2002

Well now the big question: How does it perform versus the on-board ATA?

SiSoft Sandra 2003

PCMark2002 HD Score

HD Tach Scores:
Overall Disk Read
Si 3112

AMD 766 ATA100

Burst Transfer Rate

Max Transfer Rate

Min Transfer Rate

CPU Utilization

Conclusion:

As you can see in almost all tests the Si 3112 is marginally faster than the onboard ATA100 controller. However, none of the leads that the Si3112 has will translate into a noticeable performance advantage over a standard ATA100 controller if you are using Standard ATA drives. In other tests with native SATA drives there is a performance advantage for SATA drives when placed against similar Parallel ATA drives. Drives such as Western Digital's Raptor offer SCSI-like performance for about 20% less cost. Those drives are the ones that most fully exploit SATA's capabilities.

It is clear however, Serial ATA is the future. Almost all new motherboards have the option to have SATA included onboard. Many motherboards use the Si3112 chip for SATA capability. You can be assured that if you don't want to replace your hard drives, you can still use your SATA controller with a PATA adapter and suffer no performance loss. I for one appreciate the thin cable that SATA uses, that alone would make me use it if it came with my motherboard.

PCExtreme gives the TekGems Si3112 SATA controller 4 x's!

For more info, see the TekGems product page.



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