pci bus questions

[Wolfsraider]

Sorry if this has been asked before. I've been doing google searches on my main question but have come up empty so i thought i'd try a new approach and come here (the best place to get answers)

i have been reading about pci bus values (32 bit and 64 bit)

I read that a 4 drive array ide(large drives) would max out a 32bit bus as the numbers added together for str would be greater than ata 100/133 spec, is this bad?or would this just offer diminishing returns?

that 2 scsi x15 36lp drives in a raid 0 array would also max out a 32 bit bus (most say they would never do this but to go 4 drives in a raid 5 array)but i've also read anything over 3 drives in a raid 5 array maxes out the bus, again 32 bit

i know that a 64 bit bus can handle up to four drives in a raid 0 array or 8 drives in a raid 5 array or 10 single drives before maxing out a 64 bit bus

i am looking for a raid 0 array using 2 x15 36lp drives with a ide backup drive but don't want to add the expense of a 600 dollar motherboard (call me cheap) but i don't know the adverse affects of maxing out a pci bus line

is this considered highly technical GOD i hope so i've been google searching at least 3 month's and the last two weeks every night trying to find out an answer. is this a strictly math equation?

or would you lose enough throughput to make this work?

maybe you could explain the numbers and how they work in a real world envirement or just the numbers and what they mean/do ?

thanks for reading this and for all the help this place has given me past and future

thanks mike

 

[AndyHui]

Maximum 32-bit PCI bandwidth running at 33MHz is 133MB/s.

STR maximums for the fastest IDE drives - believe it or not the Seagate Barracuda IV has the largest STR of 43MB/s.

Assuming that you have 4 IDE ports (all 4 drives being master), then 4 x 43MB/s gives you more than the 133MB/s PCI can afford.

ATA/100 or ATA133 burst rates won't matter here....the bottleneck is the PCI bus. If you increased your PCI speed to 37.5MHz (that's a usual size overclock), you would still only have 150MB/s worth of bandwidth. You need 172MB/s for full transfer rates in best conditions.

 

[Wolfsraider]

thanks andy

ps and the 64 bit bus would handle this?

also i was reading dell web site and found this?
When the requirements of the computer system exceed the bandwidth of the I/O subsystem, it is impossible to improve performance by upgrading other parts of the computer system.

does that mean once i bottle neck a system bus yhen NO other hardware will matter yikes if it does

edit oops got it 64 bit 66mhz = 533 mb so seagate4 43 x4 =<533 so no overload actually you could run 12 ide's using these numbers on a 533 mb board right?