Bill wrote:
> "peter" <> wrote in message
> news:BfOBm.5904$...
>> On all of the P55 motherboards using one PCI-e slot will run the video
>> card at x16
>> using 2 in SLI/Crossfire mode will run both at x8......not that you would
>> really notice the difference.
>> and you don't aim to use that anyways.
>> you can buy PCI-e soundcards now as well as add on SATA cards.
>> So on that note I would look closer at the 55-UD5
>>
>> peter
>
>
> It can't run anything (like an older tv-card) requiring a PCI slot, correct?
> I'm not sure
> whether there is any backward compatibility??
>
> Thanks,
> Bill
>
>
>> --
>> If you find a posting or message from me offensive,inappropriate
>> or disruptive,please ignore it.
>> If you dont know how to ignore a posting complain
>> to me and I will be only too happy to demonstrate :-)
>>
>> "Scott" <> wrote in message
>> news: ...
>>> Was going to go for a P45 but decided to go for P55 instead but can't
>>> decide on which of these 3 Gigabytes mobo's to get. My biggest concern is
>>> the number and type of expansion slots.
>>> For right now I'm only going to have a graphics card installed but I want
>>> to make sure I'm ready for any future upgrades. I don't plan on using SLI
>>> or crossfire.
>>>
>>> GA-P55-UD3R
>>> 1 PCIe 2.0 x16
>>> 1 PCIe x16 (@x4 bandwidth)
>>> 1 PCIe x1
>>> 4 PCI
>>>
>>> GA-P55-UD5
>>> 2 PCIe 2.0 x16
>>> 1 PCIe x16 (@x4 bandwidth)
>>> 2 PCIe x1
>>> 2 PCI
>>>
>>> GA-P55-UD4P
>>> 2 PCIe 2.0 x16
>>> 3 PCIe x1
>>> 2 PCI
>>>
>>> Will there ever be anything else besides a graphics card that will use
>>> PCI x16?
>>> How prevalent is PCI compare to PCIe x1?
>>>
>>>
The downloadable Gigabyte user manual, usually has an architecture
diagram, that can answer some questions. You can also make some
guesses, by examining the datasheet for the chipset. (For example,
if there seem to be too many PCI Express lanes in use in a motherboard
design, the datasheet can tell you how many lanes are on the chipset
itself. And as a result, whether there are "tricks" used
external to the chipset, which cheat on bandwidth.)
The GA-P55-UD5 is pictured here. It has two PCI slots, and those
should be backward compatible with your collection of PCI cards.
So you could reuse your sound card. The PCI card slots in
the picture, are keyed for 5V operation, just like lots
of PCI motherboards in the last ten years.
http://images17.newegg.com/is/image/newegg/13-128-402-Z09?$S640W$
With regard to PCI Express, there are a lot of combinations.
First off, the size of the connector, does not have to match
the wiring. So a PCI Express x16 motherboard connector, can have
x4 wiring on the slot. That means 12 lanes are not wired up.
If you have a PCI Express x16 slot, then a x1, x4, x8, or x16 card
will mechanically fit the socket. If there is only x4 lane wiring,
then cards can function with fewer lanes than their designed width.
They can use any power-of-two contiguously numbered lanes, starting
from lane zero. So if a PCI Express x16 slot has x4 wiring, and you
plug in an x8 card, the card gets to use x4 bandwidth, because that
is as many lanes as it sees signals on.
There are two PCI Express revisions. Revision 2 doubles the
bandwidth on a lane. So when a slot offers x8 capability,
and is Rev2, that is equal to x16 of Rev1. And that would be
4GB/sec bidirectional. By comparison, AGP8X was 2133MB/sec and
was one direction at a time while communicating.
I've been avoiding P55, and not reading any articles on it.
I'm shocked to find, the PCI Express for the graphics card,
is now hosted on the processor itself.
http://www.anandtech.com/mb/showdoc.aspx?i=3652&p=2
The GA-P55-UD5 is interesting, in that it uses a couple
peripheral chips, and hides them under a heatsink, to give
the impression there is a Southbridge. In fact, the
P55 is a single chip and lives nearest the processor.
The second chipset style heatsink, hides a couple smaller
non-Intel peripheral chips. This leads to a massive
number of SATA ports (12).
ftp://download.gigabyte.ru/manual/mb...-p55-ud5_e.pdf (page 8)
The third PCI Express x16 slot, turns out to be a real
crock. There is a lane switch. If one of the JMB362 SATA
chips is turned off, the third PCI Express slot runs
at x4. If the chip is turned on, the third PCI Express
x16 slot runs at x1.
The two video card slots, rely on the processor's PCI Express
x16 interface. To support lane switching in a similar way to
P45, four chips are placed next to the primary video card slot.
The four chips take the place of an SLI paddlecard, for selecting
the lane wiring method. So slot 1 can have x16 wiring, if the
four chips reroute x8 of wiring to the first slot. If
a second video card is installed, the four chips reroute the
wiring to the second video card slot. This eliminates the need
for the processor to have 24 lanes of wiring on its side (i.e
16 lanes to first slot, 8 lanes to second slot). The external
four chips reduce the processor interface requirement to 16
lanes (total 8GB/sec bandwidth best case).
So the P55 architecture, with the processor containing
the Northbridge, and an external chip containing the rest,
has 16 lanes on the processor and 8 lanes on the chipset.
The 8 lanes on the chipset, are throttled by the bandwidth
of the DMI, the bus that runs from the processor to the
external P55 chip. The DMI has 2GB/sec bandwidth, so that
forces the P55 lanes to be revision 1 type. So the processor
uses revision 2 lanes, while the P55 uses revision 1.
8 lanes times 250MB/sec on the P55, is equal to the
bandwidth of the DMI. But if other peripherals connected
from the P55 need bandwidth, then that also comes out
of the 2GB/sec DMI.
In my little diagram here, the "video #1 slot" runs at x16 rev2,
if only that slot has a video card. Plugging in a second card,
results in the BIOS switching the 4 chip bifurcation logic,
connecting x8 lanes worth, to the second slot (for 2 * x8 operation).
x8 (rev2)
----------------------- Processor --- Dual Channel
video #1 Core --- Memory
---+ x8 (rev2) +- i5
+-- | |
Bifurcation --+ | DMI 2GB/sec
+-- Logic |
video #2 ---+ |
x8 (rev2) P55 ----- 8 lanes PCI Express rev 1
----- PCI bus
----- SATA ports
Looking at the picture of that motherboard, the part I like the least,
is how the SATA ports are oriented. Otherwise, it is chock
full of goodness, in terms of peripheral chips.
Paul
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