Bus speed: Nvidia MCP55 vs MCP78

  • Thread starter Man-wai Chang ToDie (33.6k)
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Paul

Man-wai Chang ToDie (33.6k) said:
For a typical PCIe x16 display card, would MCP78 perform better than MCP55?

http://www.asus.com/products.aspx?modelmenu=2&model=1181&l1=3&l2=101&l3=308&l4=0

AM2_Socket
|
| HT - 1GHz, 2GT/sec x 16bit, 4GB/sec bidirectional
4GB/sec |
PCI_Express_rev1_x16 -------------- 570 Ultra
Bidirectional |
|
(Other I/O)

For your new board, there are probably several entries that would match
your notion of "MCP78", so I'll draw what a recent entry would look like.

http://www.nvidia.com/docs/IO/35382/LC_nForce_AMD_web.pdf

AM2+_Socket (can take AM2)
|
| HT - 2.6GHz, 5.2GT/sec x 16bit, 10.4GB/sec bidirectional
8GB/sec |
PCI_Express_rev2_x16 -------------- Newer_Chipset
Bidirectional |
|
(Other I/O)

The thing is, if your video card only supports Revision 1 of PCI Express,
then it continue to operate at 4GB/sec, when plugged into the new motherboard.
If you had an 8800GT for example, that is a Revision 2 card, so it would
operate at 8GB/sec when plugged into the new motherboard. An older card,
like a 6600GT, would operate at 4GB/sec.

Your existing parts may not be able to reap any improvement from a
new motherboard. Not all processors support HT3 - only the new ones
do. So an old processor would run at 1GHz, rather than 2.6GHz.
Old components + new motherboard = same old performance.

And even with all that said, some benchmarks have shown adequate
video card performance, using only PCI Express revision 1 at a
width of x4 lanes. Somewhere around 1GB/sec transfer rate, is enough
most of the time. If you had an 8800GT, and went from a Revision 1
to a Revision 2 motherboard, your frame rate would likely not change.

Next time, *please* select a motherboard when you ask your question.
Using the chipset name, especially when it does not appear in a
chart, makes it hard to answer your questions. Pick a motherboard
from the list here, if it demonstrates the hardware you're interested
in.

http://www.asus.com/products.aspx?l1=3&l2=-1

Paul
 
M

Man-wai Chang ToDie (33.6k)

http://www.nvidia.com/docs/IO/35382/LC_nForce_AMD_web.pdf
AM2+_Socket (can take AM2)
|
| HT - 2.6GHz, 5.2GT/sec x
16bit, 10.4GB/sec bidirectional
8GB/sec |
PCI_Express_rev2_x16 -------------- Newer_Chipset
Bidirectional |
|
(Other I/O)
Next time, *please* select a motherboard when you ask your question.

Thanks. I have a Radeon 4850, an AMD X2 3800+ and 6G of A-Data DDR2-800
RAM. I would like to choose Asus M3N78-PRO for a real analysis. If 3800+
was no good for the new board, I don't mind replacing my 3800+.

Thank you again.

--
@[email protected] Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and Farce be with you!
/( _ )\ (Xubuntu 8.04.1) Linux 2.6.26.5
^ ^ 12:50:01 up 2 days 17:30 2 users load average: 1.00 1.18 1.48
? ? (CSSA):
http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa/
 
P

Paul

Man-wai Chang ToDie (33.6k) said:
Thanks. I have a Radeon 4850, an AMD X2 3800+ and 6G of A-Data DDR2-800
RAM. I would like to choose Asus M3N78-PRO for a real analysis. If 3800+
was no good for the new board, I don't mind replacing my 3800+.

Thank you again.

The 4850 is PCI Express revision 2 capable. So it could run at
8GB/sec, with a new motherboard. But the 3800+ will be limited
to the older Hypertransport standard, so the processor to
chipset connection is limited to 4GB/sec. And so, a new motherboard
would not improve anything. The processor connection is still
"slow".

HD 4800 series - PCI Express revision 2.0
http://ati.amd.com/products/radeonhd4800/index.html

The Athlon64 X2 listing, consists of HT1000 processors. The AM2+ socket
processors, like Phenom, are the ones with HyperTransport 3 interfaces,
capable of higher interface rates.

http://en.wikipedia.org/wiki/List_of_AMD_Athlon_64_microprocessors#Athlon_64_X2

Also, I discover by going here, that the AM2+ processors, don't go all the
way to the limits of HyperTransport 3. For example, this Phenom datasheet
says the interface improves on the old 4GB/sec value, by only going to
7.2GB/sec, which is not even enough to support PCI Express x16 revision 2
fully (8GB/sec). So in fact, there is still room for improvement on
AMD's part. On the amdcompare.com site, you can "search" by bus speed,
but the actual part will not state in black and white, what the limit
is. So they obviously don't want you to know this :)

http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/44109.pdf

The B3 stepping parts, like the 9950, would leave the diagram like this.
Apparently the 44109.pdf document, was not updated to reflect the latest
shipping parts. They give a bit more than the 7.2GB/sec, and make it
to 8GB/sec. So if you had the M3N78-PRO motherboard, and a 9950
processor, it would look like this.

AM2+_Socket (install a Phenom 9950)
|
| HT3 - 2.0GHz, 4.0GT/sec x 16bit, 8.0GB/sec bidirectional
HD 4850 8GB/sec |
PCI_Express_rev2_x16 -------------- Newer_Chipset
Bidirectional |
|
(Other I/O)

The motherboard you selected, can handle a 140 watt processor. The 9950 is
now available in a 140W version, and a 125W version. The 125W one just
started shipping.

http://www.asus.com/products.aspx?modelmenu=2&model=2260&l1=3&l2=149&l3=676&l4=0

HTH,
Paul
 
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M

Man-wai Chang ToDie (33.6k)

The motherboard you selected, can handle a 140 watt processor. The 9950 is
now available in a 140W version, and a 125W version. The 125W one just
started shipping.
http://www.asus.com/products.aspx?modelmenu=2&model=2260&l1=3&l2=149&l3=676&l4=0

Oh no... need to upgrade a lot to fully utilize PCIe x16 2.0 slot.... I
guess I should wait and see. Thank you again, Your Honor!

--
@[email protected] Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and Farce be with you!
/( _ )\ (Xubuntu 8.04.1) Linux 2.6.26.5
^ ^ 17:36:01 up 2 days 22:16 2 users load average: 1.00 1.00 1.00
? ? (CSSA):
http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa/
 

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