Q: 64-bit PCI - 66 Mhz vs 33 Mhz networking performance?

W Bauske wsb at paralleldata.com
Tue Jul 3 17:37:39 EDT 2001


Don,

That's interesting. Do you by chance have numbers for ServerWorks
and say, a 32bit PCI config? Just curious how bad 150MB/sec is.
For what I do, that would be more than enough.

Wes

Don Holmgren wrote:
> 
> I hadn't known about an i860 problem until Patrick's mail.
> Unfortunately I can confirm the bad news.  Thanks for pointing this out,
> Patrick.
> 
> On a Dell Precision 530, gm_debug on a Myrinet PCI64B plugged into the
> 64/66 PCI bus gives:
> 
>   [root at fcwork2 bin]# ./gm_debug
>   Opening board 0, port 0
> 
>   DMA rate for 4096 Byte transfers (64bit / 66MHz bus)
>   1st: 8 pages from bogus sdma pg, 8 to bogus rdma
>           bus_read  (send) = 146 MBytes/s
>           bus_write (recv) = 315 MBytes/s
> 
>   DMA rate for 4096 Byte transfers (64bit / 66MHz bus)
>   2nd: sdma a page, rdma a page 8 times
>           bus_read  (send) = 146 MBytes/s
>           bus_write (recv) = 315 MBytes/s
> 
>   DMA rate for 4096 Byte transfers (64bit / 66MHz bus)
>   3rd: sdma and rdma to/from alternating pages (coarse grain)
>           bus_read  (send) = 146 MBytes/s
>           bus_write (recv) = 292 MBytes/s
> 
>   DMA rate for 4096 Byte transfers (64bit / 66MHz bus)
>   4th: sdma and rdma to/from alternating pages (fine grain)
>           bus_read  (send) = 146 MBytes/s
>           bus_write (recv) = 292 MBytes/s
> 
> So, even though the card is capable of sourcing data at nearly
> 250MB/sec, on this machine sends will be throttled to less than 150MB/sec.
> 
> Don Holmgren
> Fermilab
> 
> On Tue, 3 Jul 2001, Patrick Geoffray wrote:
> 
> >
> > Don Holmgren wrote:
> >
> > > The motherboards recently released for dual Pentium IV Xeons which are
> > > based on the i860 chipset have 64/66 PCI slots.  The ones that I know
> > > of are the Tyan Thunder-i860 and the SuperMicro P4DC6, as well as the
> > > motherboards used in the Dell Precision 530 and Compaq W8000.
> >
> > i860 is cheesy. It has the 64/66 label but not the performance.
> >
> > There is not a lot of choice for PCI 64/66 :
> > * ServerWorks: the best, very good PCI chipset.
> > * Intel i860: Don't wonder why Intel is using ServerWorks
> > chipset for high-end servers.
> > Yes, the 760MP is 64/33.
> >
> > For the future, ServerWorks is working on a P4 chipset and
> > the 760MPX should be 64/66. I expecte very good perf from
> > ServerWorks, but I have no clue about 760MPX PCI
> > implementation.
> >
> > For GigE or Giganet, 64/33 is good enough (peak at 250 MB/s, should
> > support full-duplex bandwidth). For SCI or Myrinet, you really want
> > 64/66.
> >
> > Regards
> >
> > Patrick
> >
> > -----------------------------------------------------------
> > |   Patrick Geoffray, Ph.D.      patrick at myri.com         |
> > |   Myricom, Inc.                http://www.myri.com      |
> > |   Cell: 865-389-8852           325 N. Santa Anita Ave.  |
> > |   Fax:  865-974-1950           Arcadia, CA 91006        |
> > -----------------------------------------------------------
> 
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