Re: Newbie Q about PCIe (and other slots) in P5Q range
- From: "Rob" <noone@xxxxxxxxxxxxxxxxx>
- Date: Mon, 26 Jan 2009 16:12:45 -0000
"Paul" <nospam@xxxxxxxxxx> wrote in message
I'm looking at buying an Asus P5Q motherboard of some kind (still unsure
which one yet) but i'm a little confused by all this stuff.
1 x PCI Express 2.0 x16 slot at max. x16 link (blue)
1 x PCI Express 2.0 x16 slot at max. x8 link (white)
2 x PCI Express x16 slot at max. x4 link (black)
1 x PCIe x1
2 x PCI
Now i understand PCI so my current Hauppauge TD-500 tv card will fit in
these fine, I also understand (i think) "1 x PCI Express 2.0 x16 slot at
max. x16 link (blue)" which if i'm right will run at 16 times faster then
x1 slot and these are used for video cards as a rule, I'm not into games
i won't be using this linking of 2 video cards or anything like that but
question is will all the other slots be useless? I know x1 will take
another tv card etc but what about all these other slots that take more
video cards, I mean by looking at Asus website it seems the "P5Q Premium"
will take 4 of them.
My basis Q is if i just have 1 video card running in the x16 slot will i
able to make use of the other slots for more normal stuff not more video
cards as this would be overkill for me, sorry for my ramblings but
you understand the point i'm trying to make.
Thanks for taking the time to read my post
Yes, you can make use of the other PCI Express slots for
more normal things. For example, if you had a TV Tuner
card with PCI Express x1 connector on it, that could plug
into any of the PCI Express slots. You could have one
video card, plus four TV Tuner cards with
PCI Express x1 interfaces. (Note that your video card
will be thick though, and will block at least one
adjacent slot. So you'll likely lose at least
one slot due to mechanical issues.)
Be aware that there still isn't a wide range of native
PCI Express hardware add-ons out there, so filling all
those PCI Express slots in a useful way today, may not
be possible. Ordinary PCI cards are still the cheapest
way to add hardware functions, and the P5Q Premium only
has two PCI slots. Your TD-500 looks like it has a
PCI connector in this photo. (The VT6210 is a PCI to
USB chip, and the video function is presumably in the
USB "DIB" chip above it.)
Part of the fun on these motherboards, is trying to figure
out what you're getting. Gigabyte makes this easy, as they
include an architecture diagram in the user manual. Asus
only provides a picture of the motherboard layout, and
doesn't label all the chips with brand and part number.
To analyze a board, you start with the chipset. You cannot
get more PCI Express functionality than the chipset offers.
So no matter what exaggerated claims the motherboard
manufacturer makes, the bandwidth is limited by the
chipset. In this case, the chipset is P45 Northbridge
and ICH10R Southbridge.
This is my take on the P5Q Premium. The blue, white, and two
black x16 sized connectors, can take smaller PCI Express
card slot connector types. The lane wiring is limited
according to how many lanes come from each chip interface.
For example, I could install a couple of x4 RAID cards in
the black slots. (Notice, how the 4GB/sec interface to
the bridge, probably doesn't run at 4GB/sec in practice.
My *guess* is the bridge chip is a revision 1.0 type,
so the P45 interface downshifts to revision 1.0 rates
or 2GB/sec. Revision 2.0 interfacesdownshift to
revision 1.0 rates, if a revision 1.0 device is
blue -----------------X16_2.0 --- 8GB/sec --------| P45 |
white -----------------X8_2.0 --- 4GB/sec --------| |
(1GB/sec) | |
black --- X4__1.0 -----bridge --- 4GB/sec --------| |
black --- X4__1.0 ----- (X8_2.0) +-----+
88E8056_GbE_Ethernet---X1_1.0 --- 0.25GB/sec -----|ICH10R|
88E8056_GbE_Ethernet---X1_1.0 --- 0.25GB/sec -----| |
88E8056_GbE_Ethernet---X1_1.0 --- 0.25GB/sec -----| |--PCI bus
88E8056_GbE_Ethernet---X1_1.0 --- 0.25GB/sec -----| | (2 slot)
white_PCI_Express------X1_1.0 --- 0.25GB/sec -----| |
| |--6 SATA
| | \
| | \
| | | |
SATA SATA SATA SATA
The stuff on the bottom allows connecting up to four SATA drives
and two PATA drives (via one ribbon cable), and the bandwidth to
support that comes through a PCI Express X1 1.0 interface. So if
you were reading from the four SATA drives simultaneously, each
drive would get about 50MB/sec or so. The six SATA connectors on the
Southbridge, won't have limitations on them, by comparison. If
you owned a Velociraptor hard drive, you'd connect it to the
ICH10R connectors. Maybe the SIL5723 chips are there, for
some kind of backup function.
I didn't include everything in that diagram - I think
I missed the Firewire chip and the sound chip :-)
While testing a 5-bay e-SATA enclosure on my P5WDH del., I
found that a 1-lane pci-e controller could only achieve 120MB/s.
I then tried it with the onboard jmicron (which is also internally
a 1-lane pci-e connection) and, guess what, that was also 120MB/s.
On a 4-lane controller, I got full SATA speeds approaching 300MB/s.
Interestingly, when I overclocked the pci-e bus by 20%, the
throughput of both the JMB and the one-lane pci-e card increased
by exactly 20%.
This is odd as each lane should be capable of 250MB/s according
to the pci-e spec. Clearly, this is not the case on this board and
I wondered if it was a design flaw or that the real-world throughput
of a single lane is actually half of what we expect?
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