USB 2.0 vs USB 3.0 (Memory Card Reader-30Mg/s vs 45Mb/s)

[synoptic12]

Greetings,
I recently purchased a compact digital camera (Sony). The camera accepts a minimum class 4 memory card. My computer is a Hp P6370t, in which 2.0 USB ports are included.
The theoretical maximum data rate in USB 2.0 is 480 Mbit/s (60 MB/s) per controller and is shared amongst all attached devices. Some chipset manufacturers overcome this bottleneck by providing multiple USB 2.0 controllers within the
southbridge.
This said, I believe that Hp incorporates Southbridge, containing three controllers. Would this mean that the "maximum" read speed would only be about 20MB/s? I'm trying to determine, 'without testing', whether a memory card rated at 30MB/s would differ than one rated at 45Mb/s. Naturally speaking of the same size memory card, (16Gb/s).
Any and all replies are very welcome. Thank you very much.

 

[groberts101]

from my experience so far.. generally not for the actual data transfers between the reader and the system unless you get a faster reader to take full advantage of the faster class cards. BUT.. even if the system does bottleneck.. the faster cards will usually give you slightly faster access times/throughput when installed in the camara itself. Depends entirely on the device used of course and you should check the mfgrs available card options and max rated speeds associated with them. No need to spend cash on faster flash if the camara can't really make use of it, right?

I tend to buy more expensive camara's and usually buy the faster rated CF cards since they do help with data throughput speeds on the device itself.

I use an eSATA/USB 2.0 external hard drive dock with multi-card reader and it's really quite fast if you have eSATA ports on the system it's attached to and the cards to take advantage of it. Then for portability sake, I also keep a USB 3.0 card reader in my laptop bag for quick and easy backwards compatability. Pretty much covers all the bases and allows the fastest transfers possible if you have the faster hardware/cards to take full advantage of it.

 

[Cerb]

The theoretical maximum data rate in USB 2.0 is 480 Mbit/s (60 MB/s) per controller and is shared amongst all attached devices. Some chipset manufacturers overcome this bottleneck by providing multiple USB 2.0 controllers within the
southbridge.

Practically all of them have done this, not just, "some." Generally, every mobo-exposed port has full bandwidth. I don't believe I've seen one not have multiple root hubs, each with multiple full-bandwidth ports, since the PII/PIII days, with USB 1.1 add-on chips. Sharing power (and over-current protection) between ports is still common, though.

Would this mean that the "maximum" read speed would only be about 20MB/s? I'm trying to determine, 'without testing', whether a memory card rated at 30MB/s would differ than one rated at 45Mb/s. Naturally speaking of the same size memory card, (16Gb/s). (sic)

20-30MB/s for large files is typical for USB 2.0. 30-35MB/s sometimes happens, but is not terribly common, and the more random the access (smaller files, generally), the lower that rate will be, even for the devices that can actually pull it off, and saturate the USB controller. IE, pulling off a video should generally be faster than a directory of typical photos. Many times, the card readers themselves will be limited, more-so than just the USB interface, so if you find a PC-integrated reader is only getting 10MB/s, don't be quick to blame USB.

480Mb/s is the rate the bus actually operates at, including all overhead. USB also is half-duplex, which causes some slow-downs. If you want to be confident you'll get > 25MB/s or so, get a USB 3.0 card reader, and plug it into a USB 3.0 port.

Also note that most cards are only rated for sequential writes, so reads of all kinds can and will vary, though reads are usually the same speed as writes in the worst cases.

 

[synoptic12]

from my experience so far.. generally not for the actual data transfers between the reader and the system unless you get a faster reader to take full advantage of the faster class cards. BUT.. even if the system does bottleneck.. the faster cards will usually give you slightly faster access times/throughput when installed in the camara itself. Depends entirely on the device used of course and you should check the mfgrs available card options and max rated speeds associated with them. No need to spend cash on faster flash if the camara can't really make use of it, right?

I tend to buy more expensive camara's and usually buy the faster rated CF cards since they do help with data throughput speeds on the device itself.

I use an eSATA/USB 2.0 external hard drive dock with multi-card reader and it's really quite fast if you have eSATA ports on the system it's attached to and the cards to take advantage of it. Then for portability sake, I also keep a USB 3.0 card reader in my laptop bag for quick and easy backwards compatability. Pretty much covers all the bases and allows the fastest transfers possible if you have the faster hardware/cards to take full advantage of it.

Thank you very much. I'm glad I joined this forum. You have definitely clarified, and presented the facts that I have been searching for, for about a day. I have read so much technical information which varies from site to site, and person to person. However, your details, if correct, have improved the meaning of technical expertise.
Irrespective of this, I did not receive a notice for a reply to my thread, in which I thought I would receive. Thank you for your technical knowledge and assistance in this area.

 

[synoptic12]

Practically all of them have done this, not just, "some." Generally, every mobo-exposed port has full bandwidth. I don't believe I've seen one not have multiple root hubs, each with multiple full-bandwidth ports, since the PII/PIII days, with USB 1.1 add-on chips. Sharing power (and over-current protection) between ports is still common, though.

20-30MB/s for large files is typical for USB 2.0. 30-35MB/s sometimes happens, but is not terribly common, and the more random the access (smaller files, generally), the lower that rate will be, even for the devices that can actually pull it off, and saturate the USB controller. IE, pulling off a video should generally be faster than a directory of typical photos. Many times, the card readers themselves will be limited, more-so than just the USB interface, so if you find a PC-integrated reader is only getting 10MB/s, don't be quick to blame USB.

480Mb/s is the rate the bus actually operates at, including all overhead. USB also is half-duplex, which causes some slow-downs. If you want to be confident you'll get > 25MB/s or so, get a USB 3.0 card reader, and plug it into a USB 3.0 port.

Also note that most cards are only rated for sequential writes, so reads of all kinds can and will vary, though reads are usually the same speed as writes in the worst cases.

*Excellent, thank you very much for your technical expertise, which has certainly clarified any doubts that I may have pondered upon. I did not read your reply, prior to posting my initial reply with the above person. You have greatly expanded upon the issue, as I understand the equation clearly. "I'm glad I joined this forum". You know, Anand is highly regarded. This is why I joined this forum. Aside from this, I'm grateful for the extremely well written answer to my question. Thank you very much.

 

[synoptic12]

Cerb- If you have some extra time, and I really do not mean to bother you, but could you, or anyone confirm one last point. You have previously stated the facts in your above reply.

1. I believe that the read speed on the camera is about 95mb/s, and write speed is about 45mb/s. In this respect, contingent upon what you stated, what memory card would you personally recommend? Naturally, I have USB 2.0 ports. I would be using video and picture format. What size card would suffice, 8gb, 16gb, 32gb and would 30mb/s be sufficient vs 45mb/s in terms of speed? From your facts, I am at the threshold, but I would appreciate your views on this. Thank you very much, and I truly appreciate your technical knowledge.

P.S.- I understand that the extra speed would be beneficial to the device itself.

 

[Cerb]

That I really can't. I have mostly faced performance issues when trying to use SD or CF cards for program data and running OSes off of, which is a whole different ballgame (random access performance), except when it comes to the USB readers.

Sandisk, Samsung, Transcend, Kingston, and Toshiba are hard brands to go wrong with, though, given a sufficient speed rating for a given card. But, make sure to buy from a reputable vendor, and preferably get retail packages only. If it looks like an awesome deal, but not from a known-good store, it could be a fake, and sometimes the sellers themselves are just as duped as the buyers.

 

[synoptic12]

That I really can't. I have mostly faced performance issues when trying to use SD or CF cards for program data and running OSes off of, which is a whole different ballgame (random access performance), except when it comes to the USB readers.

Sandisk, Samsung, Transcend, Kingston, and Toshiba are hard brands to go wrong with, though, given a sufficient speed rating for a given card. But, make sure to buy from a reputable vendor, and preferably get retail packages only. If it looks like an awesome deal, but not from a known-good store, it could be a fake, and sometimes the sellers themselves are just as duped as the buyers.

Thank you very much.Your information was very valuable. Great technical forum.