On Oct 26, 2008, at 7:31 PM, Jeremy Chadwick wrote:
This has been a concern of mine. I just bought a Dell Poweredge 2650
off of eBay, and was going to outfit it with a USB2/Firewire PCI card
so I can attach some cheap bulk storage to it for backup purposes.
The
Dell has PCI-X slots; backwards compatible with PCI, right? Try to
find a USB PCI board that doesn't require a 5V capable PCI slot..
I haven't been able to; of course it's pretty obvious in that the USB
host is supposed to supply 5V power to the peripherals.. D'oh! Oh
well.
Why do you think think the voltage provided on the USB bus is directly
proportional to the voltage provided across the PCI bus? A PCI 3.3V
expansion card (for USB ports) card *most definitely* provides 5V to
the
USB bus. The voltage increase is done with a very small amount of
circuitry on the card itself. (I've confirmed this with two
separate EE
folks I know; I showed them your message, and they're equally as
confused why you think that.)
I'm well aware of the existence of switching power supply regulators;
however the selection of USB/Firewire boards I was able to find didn't
appear to be universal cards -- at least based on the photos provided
of the actual products.
The last board I bought for another system didn't have any on-board
power source -- other than PTC fuses, the power just came off the PCI
backplane connector. It's the easy and obvious solution. Perhaps
not quite as obvious these days with 3.3V only buses.
Maybe what you're trying to say is that your PowerEdge 2650 box only
has
the old 5V PCI slots, thus you need a USB PCI card that works in such
scenarios? If so, I'm baffled as to why you're having such
difficulty.
Many PCI cards (including PCI USB cards -- I've Googled and found
many!)
are "Universal PCI" cards (keyed to work on both 3.3V and 5V PCI
slots),
and those will work fine. How to determine what's what:
http://en.wikipedia.org/wiki/Image:PCI_Keying.png
The 2650 only has 3.3V slots. This determined by the physical keying
of the connectors on the riser. I looked a bunch of boards on Amazon,
and they
didn't appear to be universal PCI cards. And if you look at the photos,
there's nothing there that would appear to be a small switcher to
generate
the +5V for the USB interface.
The Dell PowerEdge 2650 Systems Installation and Troubleshooting Guide
indicates that the mainboard uses a riser board to provide three (3)
PCI-X slots:
http://support.dell.com/support/edocs/systems/pe2650/en/it/5g375aa0.htm#1046001
Googling around for a few minutes turns up some photos of the 6H580
riser board, which confirm the slots are 64-bit PCI-X 3.3V:
http://cgi.ebay.com/Dell-6H580-PowerEdge-2650-PCI-Riser-Board-Card-TESTED_W0QQitemZ200218132010QQcmdZViewItem
But what revision of PCI-X? Well, the speeds (MHz) available for each
slot change depending upon what's installed where. Here's that
reference:
http://support.dell.com/support/edocs/systems/pe2650/en/it/5g375c60.htm#1059976
Which says the maximum rate is 133MHz, confirming these are PCI-X 1.0
slots.
My bandwidth needs are modest, just to run the USB/Firewire
interfaces. The
2650 is pretty cost effective on ebay these days, though you're
constrained
to using SCA SCSI drives which are somewhat more expensive than your
generic
SATA drives these days. I've got 5 bays populated with 73GB drives
which
is sufficient for the usual email/www server, I'd like to drop some
larger,
less performant drives for over-the-net backup use.
The search continues..
louie
Have fun. :-)
--
| Jeremy Chadwick jdc at parodius.com |
| Parodius Networking http://www.parodius.com/ |
| UNIX Systems Administrator Mountain View, CA, USA |
| Making life hard for others since 1977. PGP: 4BD6C0CB |
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