SATA AM1808

mickael

Other Parts Discussed in Thread: AM1808

Hi ,

I want to know if we can connect directly a SSD disk on the sata port ? is the liux driver are ready to manage it ? What is the max capacity that we can connect on it ?

thanks

over 15 years ago

0 Bernie Thompson TI over 15 years ago

TI__Mastermind 41665 points

mickael said:
I want to know if we can connect directly a SSD disk on the sata port ?

You can connect a drive directly to the SATA port, even a SSD, it should show up like a normal hard disk.

mickael said:
is the liux driver are ready to manage it ?

The SATA drivers are in place, however for the out of the box kernel you may have to disable port multiplier support in your kernel and rebuild, as mentioned in this thread.

mickael said:
What is the max capacity that we can connect on it ?

The theoretical maximum capacity would be 144,115,188,075,855,872 (512*2^48) bytes.

0 Yulin over 15 years ago in reply to Bernie Thompson TI

Expert 1625 points

Hi there,

Ideal bandwidth of SATA II is ~300MB/sec.
However, our test using a SATA II SSD drive on AM1808EVM+SDK only achieves 26MB/s, close to
http://processors.wiki.ti.com/index.php/DaVinci_PSP_03.20.00.11_Device_Driver_Features_and_Performance_Guide.
but far less than R:100MB/s and W:70MB/s on PC.
What is the bandwidth bottleneck ?

Yulin.

0 tlee over 15 years ago in reply to Yulin

TI__Guru 62975 points

Yulin,

In case you don't find your answer here, you might receive more feedback about the SATA Linux driver performance from the Linux forum: http://e2e.ti.com/support/embedded/f/354.aspx

-Tommy

0 Jeffrey McCasland over 14 years ago in reply to tlee

Prodigy 140 points

Yulin,

Has TI characterized the bandwidth of the AM1808 and/or L138 SATA interface? or to ask another way, are their any TI generated benchmark numbers for the SATA interface?

Thank,

Jeffrey McCasland

0 clam over 14 years ago in reply to Jeffrey McCasland

TI__Expert 8785 points

The link Yulin provided in the post, http://processors.wiki.ti.com/index.php/DaVinci_PSP_03.20.00.11_Device_Driver_Features_and_Performance_Guide, is TI's benchmark numbers based on the device drivers provided from the DaVinci Linux PSP package.

You can probably find more feedback on the Linux driver performance from the Linux Embedded System forum: http://e2e.ti.com/support/embedded/f/354.aspx

--Christina

0 Jeffrey McCasland over 14 years ago in reply to clam

Prodigy 140 points

Hello Christina,

Then just to clarify...even though the OMAP L138 specification states the SATA interface 'supports SATA 3.0GBPS', the device has only been validated at 0.168GBPS (or 21 MBPS *8). Is this correct?

0 Jeffrey McCasland over 14 years ago in reply to Jeffrey McCasland

Prodigy 140 points

okay...let me fix my units....0.168 Gbps (giga bits per second)....21MBps (21 MBytes per seconds)....

Thanks,

Jeffrey

0 clam over 14 years ago in reply to Jeffrey McCasland

TI__Expert 8785 points

The numbers are based off the device driver performance. With better software optimization, I assume SATA can perform faster. However, I'm not a SATA expert, so I do not have the insight on the maximum hardware performance. Maybe someone with a better SATA expertise can comment on the hardware performance.

--Christina

0 Jeffrey McCasland over 14 years ago in reply to clam

Prodigy 140 points

Christina,

Cool! Therein lies my interest. I chose the L138 for my system based on specification numbers listed in TI's data sheet. However, the results advertised by the Linux developers is no where close to the advertised data rate. I mean an order of magnitude less! If the silicon is capable of sustaining even one sixth the data rate (i.e. 50MBytes/second), then I might be inclined to have one of my software engineers work on optimizing the software driver for our application where we only need 50 MByte/second write/read data rate. Does TI perform a system validation of its silicon devices against the advertisied specification?

Thanks again,

Jeffrey

0 clam over 14 years ago in reply to Jeffrey McCasland

TI__Expert 8785 points

I contacted our SATA expert and this is what he said:

Theoretical throughput
- Gen2 raw speed is: 3 Gbits/Sec. 3,000 Mbits/Sec. Since each byte is encoded to 10 bits, there is a 25% overhead, so the 3Gbits/Sec=300Mbytes/Sec.
- Gen1 raw speed is: 1.5 Gbits/Sec = 150 Mbytes/Sec.
When running standalone SATA tests, the maximum write performance seen for GEN1 is 120Mbytes/sec. GEN2 is also around the same. Read performance is slightly faster.
As you might see, that there is not much to be gained by moving to GEN2. This is because most of the Hard Disk Drives do not do a sustain transfer. There is a whole lot of flow control.

Therefore, the SATA hardware should be able to do the 50Mbyte/second per you application if software is optimized correctly.

--Christina

0 Jeffrey McCasland over 14 years ago in reply to clam

Prodigy 140 points

Thank you Christina!

You are my hero!

Sincerely,

Jeffrey

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