16x PCI Express graphics + 4x PCIe SAS controller -> how would itwork out electrically?

[Squat'n Dive]

When I plug a SAS pcie controller into the 16x slot meant for the
second graphics card
does the primary graphics card switch to 8x or 12x?

Is it better to plug the SAS controller into the second or the third
pcie 16x sized slot.
Thanks.

 

[Paul]

When I plug a SAS pcie controller into the 16x slot meant for the
second graphics card
does the primary graphics card switch to 8x or 12x?

Is it better to plug the SAS controller into the second or the third
pcie 16x sized slot.
Thanks.

Motherboard make and model ?

Some motherboards, have multiplexer chips, that change the bus
configuration as a function of slot detection. If the secondary
slot "card_present" signal is grounded, the multiplexer chips
change how the bus lanes are wired. That is how they change from
16x on primary, to two slots of 8x for example.

For more info, give the motherboard make and model.

Paul

 

[Squat'n Dive]

Undecided. Contemplating a sub $300 X58 board, i7 920
and 3-6 gb of kingston 1066 DDR3 (ECC).
if X58 can do ECC (my asus X38 board had no problem).
If no ECC is supported in X58 I'll consider P55.

It might also help to know what video card is in the system,
and whether any highly demanding modern 3D games are being
played... if not, what's it matter if the video card isn't
in 16X mode?

In this case I'd like to know during at which graphics card model
it becomes useless to spend more money on graphics card.

I suppose Radeon 4870 would not exceed the pcie x8 bandwidth,
would it?

 

[Paul]

Undecided. Contemplating a sub $300 X58 board, i7 920
and 3-6 gb of kingston 1066 DDR3 (ECC).
if X58 can do ECC (my asus X38 board had no problem).
If no ECC is supported in X58 I'll consider P55.


In this case I'd like to know during at which graphics card model
it becomes useless to spend more money on graphics card.

I suppose Radeon 4870 would not exceed the pcie x8 bandwidth,
would it?

The X58 has two full x16 interfaces on the chip, and a x4, for a total
of 36 lanes. It may also be arranged as four x8 slots plus x4. You can
get the information from the X58 datasheet. (There are block
diagrams showing bus interfaces.)

http://www.intel.com/Assets/PDF/datasheet/320838.pdf

Core i7 does not have ECC. I don't know whether other followup
desktop products will change that or not. The memory controller
is on the processor, which means the ECC support is part of the
processor as well.

If you're serious about ECC, you need an Intel processor that
has ECC on the interface. The Xeon version of i7 does that.

W3580 LGA1366 Xeon, 3 channel memory with ECC.
http://processorfinder.intel.com/details.aspx?sSpec=SLBET

http://www.intel.com/p/en_US/products/server/processor/xeon3000/technical-documents

W3580 datasheet.
http://www.intel.com/Assets/PDF/datasheet/321332.pdf

Page 76:

DDR{0/1/2}_ECC[7:0] Check Bits (enough for three channels)

Compare that to the desktop Core i7 LGA1366. Page 67 and 68, don't
have those ECC signals.

http://download.intel.com/design/processor/datashts/320834.pdf

Looking at the land grid signal definitions, as an example,
land C36 is an ECC signal on the Xeon, while it is "reserved" on
the desktop Corei7. That means Intel had room for it, but chose
market differentiation. Unlike AMD, where ECC is available on virtually
everything.

This is an example of a new Xeon LGA1366 board, with toys aplenty.

http://www.tyan.com/product_board_detail.aspx?pid=641

*******

The last article that addressed PCI Express bandwidth requirements,
was an article by Tomshardware years ago. The first chart, testing
with SpecViewPerf, shows a heavy PCI Express dependency. But if you
look at the gaming charts that follow, they're less dependent on
the bus.

http://www.tomshardware.com/reviews/sli-coming,927-9.html

I see proof of that, when I test and compare some crummy cards
like a FX5200 AGP 8X versus FX5200 PCI. The gaming benchmarks
are almost the same, even though the AGP 8x has 2166MB/sec bandwidth
available to it.

Paul

 

[DevilsPGD]

In message
<f205b4b9-6af4-4cbe-ae86-3cb8f8031f7d@j32g2000yqh.googlegroups.com>

When I plug a SAS pcie controller into the 16x slot meant for the
second graphics card
does the primary graphics card switch to 8x or 12x?

It shouldn't, although some boards will.

Is it better to plug the SAS controller into the second or the third
pcie 16x sized slot.

Odds are good that if you have three 16x slots your board isn't one of
the earlier ones that drops both slots to 8x when you use the first two
8x.

 

[Squat'n Dive]

The X58 has two full x16 interfaces on the chip, and a x4, for a total
of 36 lanes. It may also be arranged as four x8 slots plus x4. You can
get the information from the X58 datasheet. (There are block
diagrams showing bus interfaces.)

http://www.intel.com/Assets/PDF/datasheet/320838.pdf

Core i7 does not have ECC. I don't know whether other followup
desktop products will change that or not. The memory controller
is on the processor, which means the ECC support is part of the
processor as well.

If you're serious about ECC, you need an Intel processor that
has ECC on the interface. The Xeon version of i7 does that.

W3580 LGA1366 Xeon, 3 channel memory with ECC.http://processorfinder.intel.com/details.aspx?sSpec=SLBET

http://www.intel.com/p/en_US/products/server/processor/xeon3000/techn...

W3580 datasheet.http://www.intel.com/Assets/PDF/datasheet/321332.pdf

    Page 76:

    DDR{0/1/2}_ECC[7:0]     Check Bits (enough for three channels)

Compare that to the desktop Core i7 LGA1366. Page 67 and 68, don't
have those ECC signals.

http://download.intel.com/design/processor/datashts/320834.pdf

Looking at the land grid signal definitions, as an example,
land C36 is an ECC signal on the Xeon, while it is "reserved" on
the desktop Corei7. That means Intel had room for it, but chose
market differentiation. Unlike AMD, where ECC is available on virtually
everything.

This is an example of a new Xeon LGA1366 board, with toys aplenty.

http://www.tyan.com/product_board_detail.aspx?pid=641

Checked the prices for the board alone and am leaning towards X48 now
as the result
of Intel's irresponsibility.
Thank you Paul for an exhaustive explanation.