Anyone real familiar with PCI specs? I got some questions.

[Mr.Diggler]

These are stemming from this thread in Hot Deals: Thread

If you go to that thread, scroll about 12 posts down until you see a bold "START HERE" surrounded by ********** lines. It's basically a conversation between computer and I (that sounds weird) concerning PCI specs.

As I understand it, our consumer based boards are 33MHz with 32bit width allowing for a theoretical max of 133MB/s transfer through. Am I stating that correctly?

Server and workstation boards sometimes have 64bit PCI and even 133MHz clock speeds with PCI-X.

computer has Sandra screen captures showing transfers in the 500MB/s range though. What am I not understanding here? This would seem impossible to me so I must be confusing something in my head about PCI.

 

[tcsenter]

First, Sandra has a lot of nifty colorful bar graphs, and is great as an information reporting and listing tool, but as a benchmarking and performance measuring application it stinks and is often inaccurate, with the exception of the memory bandwith tests, which are not necessarily accurate, they are just very consistent when comparing across different configurations.

He stated he was using the Promise Ultra100/133/TX2 and the MAX theoretical bandwidth limit on these Promise cards is 133MBs using 33MHz PCI bus and 266MBs using 66MHz. However, burst transfer rates are still maxed theoretically at 100MBs and 133MBs, using ATA100 and ATA133 drives, respectively. The Promise Ultra/TX2 supports 66MHz PCI bus, but it only does it at 32bit, not 64bit.

The 66MHZ PCI bus was part of the PCI 2.1 specification, BTW. Yes, its that old.

 

[Mr.Diggler]

So it was probably a mismeasurement by Sandra or, as someone pointed out to me in PM, possibly a measurement of the drives transfer speed from cache directly instead of from memory, etc.


A sort of related question...are there any good consumer boards that offer 64bit and/or 66MHz PCI slots? I'd love a version of the P4T533 with that...just for kicks.

 

[computer]

I also got similar results using HDtach bench program. Does anyone know how to paste images into these pages? I could upload to my website but I have so many things like this there now (ie, images linked to outside sources from my domain) I hate to keep adding more.

(BTW, FYI, my name is Clint)

 

[Peter]

There are no consumer grade chipsets that offer 66-MHz or 64-bit PCI bus.

Why? If you do 66 MHz PCI, you need to have two PCI busses - simply because you can't have more than two slots on a 66 MHz PCI bus, and also because 33-MHz cards would kick it back to 33 for everything.

AMD's 760MPX chipset has that twin bus arrangement, VIA's DDR chipsets could technically do it with an extra chip (but at the cost of losing AGP), Intel's big guns have it, ServerWorks chipsets too, but nothing one could build an affordable mainboard with.

regards, Peter

 

[computer]

I (and I'm sure some others) have some 66mhz PCI cards; for one, the Intel 1gb (10/100/1000mb) PRO NIC. It would be nice to find a P4 or even an Athlon Tbird/XP, mobo that supported it. I realize that since DSL and cable isn't anywhere near even the 10mb/sec spec, it still at least uses the 66mhz PCI bus which should possibly speed up PCI bus requests to the card. (It's also backward compatible with 33mhz).

 

[tcsenter]

I also got similar results using HDtach bench program. Does anyone know how to paste images into these pages?

You cannot paste images into the message area, I do not believe. You can only link to an image. There are a few AT members who have pic servers you can use, but I forget who they are.

Even still, 500MB/s exceeds the capabilities of anything currently available in a consumer grade platform, and most everything that is available in a server platform. I'm not sure what the top-end servers are capable of, so I cannot say that 500MB/s is totally unattainable at this time. Certainly not through a 32bit Promise Ultra100/TX card, not even at 66MHz.