Okay so I'm not great at reading technical papers and wiki describes expresscard both ways (IMO). So does expresscard 1.0 use both PCIe x1 and USB2.0 simultaneously or can it only use one at a time?
Expresscard USB/PCIe
- Thread starter Pandamonium
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- Mar 4, 2000
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Not sure what you are asking. Expresscard is a standard for use mainly in laptops. It comes in 3 sizes these days. 75mm, 54mm, and 34mm. The 75mm replaces the old Cardbus PCMCIA device. They are used to provide USB ports, eSATA ports, Firewire ports, etc. What do you mean by "simultaneously?" The USB ports depend on the exact Expresscard used. USB 2 ports are backward compatible to USB 1.
PCIExpress is a circuit board format for use in desktops. It is the replacement for PCI slots with greater bandwidth. The connection fingers are different.
It would help to iknow what you are trying to do.
PCIExpress is a circuit board format for use in desktops. It is the replacement for PCI slots with greater bandwidth. The connection fingers are different.
It would help to iknow what you are trying to do.
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Expresscard's bandwidth is at least in part supplied by a PCIe x1 lane. However, it can also access the USB 2 bus for bandwidth. (at least according to wiki- I might have read it earlier on some expresscard spec sheet, but I don't remember)
My question is can an Expresscard device access the PCIe and USB 2 buses simultaneously?
There's an external GPU/dock called the ViDock 2. It basically saturates the PCIe bus with video signals if you're doing high-demand stuff with any modern GPU. The ViDock2 also acts as a USB 2.0 hub. I'm wondering if using the USB hub side of it will degrade video bandwidth. If the Expresscard spec allows for simultaneous use of both buses, then I'd imagine that the ViDock 2 is indeed using both buses to provide video and USB.
I'm quite interested in it because a) the ViDock 2 supports Expresscard 2.0, which should give effective PCIe x2 bandwidth and b) my tablet's 4500MHD just won't cut it if I want to try replacing my desktop.
edit: I'm pretty certain Expresscard only has 54mm and 34mm standards. You might be getting the 75mm figure from the length of the cards. Both 34mm and 54mm cards must be 75mm long to extend from the edge of a laptop to the internal connector. The only weird thing is that the 54mm cards can't be rectangular, ostensibly so that 34mm cards won't wobble when they're put in 54mm slots.
My question is can an Expresscard device access the PCIe and USB 2 buses simultaneously?
There's an external GPU/dock called the ViDock 2. It basically saturates the PCIe bus with video signals if you're doing high-demand stuff with any modern GPU. The ViDock2 also acts as a USB 2.0 hub. I'm wondering if using the USB hub side of it will degrade video bandwidth. If the Expresscard spec allows for simultaneous use of both buses, then I'd imagine that the ViDock 2 is indeed using both buses to provide video and USB.
I'm quite interested in it because a) the ViDock 2 supports Expresscard 2.0, which should give effective PCIe x2 bandwidth and b) my tablet's 4500MHD just won't cut it if I want to try replacing my desktop.
edit: I'm pretty certain Expresscard only has 54mm and 34mm standards. You might be getting the 75mm figure from the length of the cards. Both 34mm and 54mm cards must be 75mm long to extend from the edge of a laptop to the internal connector. The only weird thing is that the 54mm cards can't be rectangular, ostensibly so that 34mm cards won't wobble when they're put in 54mm slots.
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- Mar 4, 2000
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My laptop has a 54mm slot that accepts Cardbus and Expresscards (34 or 54 mm. It directly accesses the system bus but AFIAK (reading the Wiki article) it has nothing to do with USB. My travelling 3G device is a Novatel C777 which is a combo 34 in 54.
http://pics.bbzzdd.com/users/Corky-G/C-777.JPG
The bottom one is the 34. The actual length of the insertable frame is about 90mm. Since Expresscard 2 has its own bandwidth directly from the system bus, it has no need to access the USB bus with less bandwidth. It seems that ViDock 2 does it directly - no USB reference.
http://www.harmonicinversion.com/in...n=com_virtuemart&Itemid=34&vmcchk=1&Itemid=21
And this user's experience is interesting . . .
http://forum.notebookreview.com/showthread.php?t=397296
http://pics.bbzzdd.com/users/Corky-G/C-777.JPG
The bottom one is the 34. The actual length of the insertable frame is about 90mm. Since Expresscard 2 has its own bandwidth directly from the system bus, it has no need to access the USB bus with less bandwidth. It seems that ViDock 2 does it directly - no USB reference.
http://www.harmonicinversion.com/in...n=com_virtuemart&Itemid=34&vmcchk=1&Itemid=21
And this user's experience is interesting . . .
http://forum.notebookreview.com/showthread.php?t=397296
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I'm looking at the photos you took- I'm pretty sure your laptop has a standard PCMCIA/Cardbus/PC-Card port and you've got an Expresscard/34 device docked in a to PCMCIA-Expresscard adapter. http://en.wikipedia.org/wiki/ExpressCard has pretty good images of Expresscard 54 and 34 cards compared to Cardbus/PCMCIA/PC-Card (whichever one you want to call it).
PCMCIA has access to a 32bit PCI system bus, for something like 133.3 MB/sec bandwidth. Expresscard 1.0 has access to at least a 1x PCIe lane, for a maximum of bandwidth of something like 300 MB/sec. Expresscard 1.0 can also access the USB bus, for a bandwidth of 60 MB/sec. Expresscard 2.0 improves things quite a bit, but it's not on the market yet. Here's a table I just found http://en.wikipedia.org/wiki/List_of_device_bandwidths#Portable
So the big picture of why I'm wondering this at all goes back to the ViDock 2. I'm thinking about buying one so that I can phase out my desktop and just use my tablet (4500MHD graphics are pretty piss poor). It's retails for almost $400 and is hard to find below that because there's only one north American distributor (the promotional price they've got now is actually kind of tempting...). I'm hesitant to blow that much money on what is basically an external GPU / USB hub combo, but if it'll last me a while, I might pick one up. The ViDock 2 is Expresscard 2.0 compatible, so it could potentially last very long.
It's complicated though, because I would want to use it as both an external GPU and a USB hub. It's not a docking station, but it's pretty close. I could bring my tablet home, plug in power, and slide the ViDock adapter into the Expresscard slot for all my peripherals. But especially now, if Expresscards cannot simultaneously access both the PCIe and USB buses, then I've got a problem. Because then for my use, everything I plug into the USB ports is going to take away from what little video bandwidth there is to begin with.
Most current midrange GPUs are all on PCIe x16. Some might be x8, I don't know. The point is, bus bandwidth isn't really limiting a GPU at x16 yet. But when you dial it down to a 1x lane (like a ViDock must do in Expresscard 1.0 mode), bandwidth starts to become a limiting factor. http://www.tomshardware.com/reviews...tml?xtmc=pcie_express_scaling_analysis&xtcr=1 Tom's Hardware did an analysis of just that a long time ago with some old GPUs. They only compared an 8800GTS vs an X1900XTX. Not quite current generation, but pretty close. The nVidia pretty much needs all 16 lanes. You see FPS drop proportionally to PCIe lanes. The AMD is another story. It gives about 80% performance at PCIe x1, and the differences between x4, x8, and x16 performance are minimal.
So if Expresscard can only run one of the two buses at once, then using the ViDock's hub function directly takes away from video performance and I probably won't be interested until Expresscard 2.0 is prevalent on laptops. If, however, Expresscard 1.0 can access both buses simultaneously, then I can use a ViDock happily, today, as a pseudo docking station. I'd also know that later on down the road, I can upgrade the GPU and stick it the ViDock in an Expresscard 2.0 capable laptop, and be good to go with USB 3.0 for the hub and PCIe x2 for the GPU.
PCMCIA has access to a 32bit PCI system bus, for something like 133.3 MB/sec bandwidth. Expresscard 1.0 has access to at least a 1x PCIe lane, for a maximum of bandwidth of something like 300 MB/sec. Expresscard 1.0 can also access the USB bus, for a bandwidth of 60 MB/sec. Expresscard 2.0 improves things quite a bit, but it's not on the market yet. Here's a table I just found http://en.wikipedia.org/wiki/List_of_device_bandwidths#Portable
So the big picture of why I'm wondering this at all goes back to the ViDock 2. I'm thinking about buying one so that I can phase out my desktop and just use my tablet (4500MHD graphics are pretty piss poor). It's retails for almost $400 and is hard to find below that because there's only one north American distributor (the promotional price they've got now is actually kind of tempting...). I'm hesitant to blow that much money on what is basically an external GPU / USB hub combo, but if it'll last me a while, I might pick one up. The ViDock 2 is Expresscard 2.0 compatible, so it could potentially last very long.
It's complicated though, because I would want to use it as both an external GPU and a USB hub. It's not a docking station, but it's pretty close. I could bring my tablet home, plug in power, and slide the ViDock adapter into the Expresscard slot for all my peripherals. But especially now, if Expresscards cannot simultaneously access both the PCIe and USB buses, then I've got a problem. Because then for my use, everything I plug into the USB ports is going to take away from what little video bandwidth there is to begin with.
Most current midrange GPUs are all on PCIe x16. Some might be x8, I don't know. The point is, bus bandwidth isn't really limiting a GPU at x16 yet. But when you dial it down to a 1x lane (like a ViDock must do in Expresscard 1.0 mode), bandwidth starts to become a limiting factor. http://www.tomshardware.com/reviews...tml?xtmc=pcie_express_scaling_analysis&xtcr=1 Tom's Hardware did an analysis of just that a long time ago with some old GPUs. They only compared an 8800GTS vs an X1900XTX. Not quite current generation, but pretty close. The nVidia pretty much needs all 16 lanes. You see FPS drop proportionally to PCIe lanes. The AMD is another story. It gives about 80% performance at PCIe x1, and the differences between x4, x8, and x16 performance are minimal.
So if Expresscard can only run one of the two buses at once, then using the ViDock's hub function directly takes away from video performance and I probably won't be interested until Expresscard 2.0 is prevalent on laptops. If, however, Expresscard 1.0 can access both buses simultaneously, then I can use a ViDock happily, today, as a pseudo docking station. I'd also know that later on down the road, I can upgrade the GPU and stick it the ViDock in an Expresscard 2.0 capable laptop, and be good to go with USB 3.0 for the hub and PCIe x2 for the GPU.
- Mar 4, 2000
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The Lenovo T60 has two slots. The lower is a PC Card type I. The upper is a 54mm Expresscard slot. It accepts 34mm card snugly when inserted in the left side of the Expresscard slot. This shows the layout - 2 separate slots electrically:
http://pics.bbzzdd.com/users/Corky-G/slots.jpg
I'm quite sure neither accesses the USB bus at all.
http://pics.bbzzdd.com/users/Corky-G/slots.jpg
I'm quite sure neither accesses the USB bus at all.
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The expresscard specification allows for expresscards to interface with the motherboard via USB or PCIe (x1). The expresscard port itself is essentially a direct link to the pcie bus and the usb host controller. The choice is with the designer of the expresscard module whether to use the usb or pcie bus, or both. The question is, does the vidock send usb traffic through the pcie bus or the usb bus portion of the expresscard interface. There is no reason they can't use both buses other than cost savings in making the vidock. You should look at documentatoin of the vidock to see if it uses both buses or just the pcie
unfalliblekrutch: thanks. I was hoping for a link to some spec but what you were saying makes sense. I dug around a bit more and found an official document that almost confirms it. Tthe expresscard specs are actually not too difficult to understand- I just figured they'd be way over my head since I haven't been following hardware dev. as much in the last few years. Here's the link for ref: http://www.expresscard.org/web/site/standardsummary.jsp The relevant passage is under the heading "ExpressCard Interface". In short, Expresscard slots must support both PCIe x1 and USB bus access. Expresscards themselves can support either or both. The summary doesn't explicitly say whether cards and slots can support both simultaneously, but I get the feeling that if they couldn't, it would be written.
corkyg: I realize you're trying to help and I thank you for that, but I think you've got the wrong understanding of Expressscard and maybe PC Card. While I was looking through the official Expresscard site I found this page: http://www.expresscard.org/web/site/graphics.jsp One of the images is a side-by-side comparison of 54, 34, and PC Card. The first set of pictures you took of your mobile broadband is definitely an expresscard 34 plugged into a PC card adapter. If you go to http://www.expresscard.org/web/site/standardsummary.jsp, it confirms that Expresscard spec requires slots provide PCIe x1 and USB 2 bus access. I did some more reading (http://www.pcmcia.org/faq.htm#terms) and some of the stuff I wrote is definitely wrong. PCMCIA is the overseeing body (like IEEE) and PC Card/Cardbus are the interchangeable terms unless you want to get into semantics. PC Card usually communicates over the PCI bus (older cards might use some kind of 16 bit bus that is ISA-like). So a PC card has access to 133 MB/sec of maximum theoretical bandwidth. The PCMCIA website's FAQ wording suggests that Expresscard can only access either the PCIe x1 or USB 2 bus at one time, while the Expresscard group's summary just stops short of explicitly saying Expresscards can access both buses simultaneously. Since one is a general FAQ by the overseeing body and the other is a summary of a spec by the spec group, I'm going to side with what Expresscard has to say.
In any event, it definitely comes down to how VillageTronic designed the ViDock 2. I just sent them an email asking that. I can't imagine an engineer would allow the trade off of saving a couple bucks on controllers to potentially cause a 20% performance hit on the main purpose of the ViDock. (PCIe x1 = 2.5 Gbit/sec = 312.5 MB/sec; USB 2.0 = 480 Mbit/sec = 60 MB/sec; 60 MB/sec / 312.5 MB/sec = 19%) I mean, it's pretty clear that any worthwhile GPU made in the last 3-4 yrs would be bandwidth limited by a PCIe x1 lane. Besides, I think that supporting a USB 2.0 controller off the PCIe x1 lane is more expensive than just adding a simultaneous link to the existing USB 2.0 controller in the host computer's expresscard slot. I'll report here when I hear back from them, but my suspicion (and hope) is that the ViDock 2 can use both buses simultaneously.
corkyg: I realize you're trying to help and I thank you for that, but I think you've got the wrong understanding of Expressscard and maybe PC Card. While I was looking through the official Expresscard site I found this page: http://www.expresscard.org/web/site/graphics.jsp One of the images is a side-by-side comparison of 54, 34, and PC Card. The first set of pictures you took of your mobile broadband is definitely an expresscard 34 plugged into a PC card adapter. If you go to http://www.expresscard.org/web/site/standardsummary.jsp, it confirms that Expresscard spec requires slots provide PCIe x1 and USB 2 bus access. I did some more reading (http://www.pcmcia.org/faq.htm#terms) and some of the stuff I wrote is definitely wrong. PCMCIA is the overseeing body (like IEEE) and PC Card/Cardbus are the interchangeable terms unless you want to get into semantics. PC Card usually communicates over the PCI bus (older cards might use some kind of 16 bit bus that is ISA-like). So a PC card has access to 133 MB/sec of maximum theoretical bandwidth. The PCMCIA website's FAQ wording suggests that Expresscard can only access either the PCIe x1 or USB 2 bus at one time, while the Expresscard group's summary just stops short of explicitly saying Expresscards can access both buses simultaneously. Since one is a general FAQ by the overseeing body and the other is a summary of a spec by the spec group, I'm going to side with what Expresscard has to say.
In any event, it definitely comes down to how VillageTronic designed the ViDock 2. I just sent them an email asking that. I can't imagine an engineer would allow the trade off of saving a couple bucks on controllers to potentially cause a 20% performance hit on the main purpose of the ViDock. (PCIe x1 = 2.5 Gbit/sec = 312.5 MB/sec; USB 2.0 = 480 Mbit/sec = 60 MB/sec; 60 MB/sec / 312.5 MB/sec = 19%) I mean, it's pretty clear that any worthwhile GPU made in the last 3-4 yrs would be bandwidth limited by a PCIe x1 lane. Besides, I think that supporting a USB 2.0 controller off the PCIe x1 lane is more expensive than just adding a simultaneous link to the existing USB 2.0 controller in the host computer's expresscard slot. I'll report here when I hear back from them, but my suspicion (and hope) is that the ViDock 2 can use both buses simultaneously.
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- Mar 4, 2000
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OK - but I go by the Lenovo specs. It specifically states there are two slots - one PC card and the other Expresscard 54 which accepts Expresscard 34s. They directly access the system bus.
Just for interest, I have two eSATA cards - one PC and the other Express 34. The Express34 card is noticeably faster.
http://pics.bbzzdd.com/users/Corky-G/eSATAlap.jpg
Just for interest, I have two eSATA cards - one PC and the other Express 34. The Express34 card is noticeably faster.
http://pics.bbzzdd.com/users/Corky-G/eSATAlap.jpg
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