pci bus speed

[ShadowBlade]

how fast is a normal pci bus?
i need to know how well a scsi controller would do in pci

 

[MobiusPizza]

33Mhz for PCI
66Mhz for PCI-X (not PCI Express)

 

[n0cmonkey]

33mhz 32bit
66mhz 64bit

I think you can have 66mhz 32bit slots too.

I think PCI-X is 66mhz-133mhz, but I'm not positive.

 

[ShadowBlade]

what would that be in MB per second

 

[V00D00]

Originally posted by: n0cmonkey
33mhz 32bit
66mhz 64bit

I think you can have 66mhz 32bit slots too.

I think PCI-X is 66mhz-133mhz, but I'm not positive.

66mhz 64 bits per second translates to MB/sec like this:

66,000 hz (means once per second) x 64 bits = 4224000

/ 8 (for bits to bytes) = 528000

/ 1024 (for B -> MB) = 515.625 MegaBytes / Second

128.9MB/sec
515.6MB/sec
respectively

You can find those and even more specs at the PCI specification website:
http://www.pcisig.com/specifications/pcix_20/

 

[montag451]

Theoretical MB = (mhz x bits)/128
i think

 

[n0cmonkey]

This might be right. I'm too lazy to do a quick search to figure it out. :beer:

 

[Concillian]

A normal 32bit/33MHz PCI slot like is on just about every desktop board made is 133MB/sec

Also PCI bus is shared so if you have anything else on the PCI bus (IDE, netowrk) it needs to share that 133MB/sec.

For SCSI cards it doesn't make sense to get more than a SCSI 160 board unless you have some Captain Insano hard drive setup. Even 15k drives top out in the 50-70 MB/sec range, so you'd need 2-3 transferring at the SAME TIME for SCSI 160 to be limiting things.

 

[V00D00]

Originally posted by: Concillian
A normal 32bit/33MHz PCI slot like is on just about every desktop board made is 133MB/sec

Also PCI bus is shared so if you have anything else on the PCI bus (IDE, netowrk) it needs to share that 133MB/sec.

For SCSI cards it doesn't make sense to get more than a SCSI 160 board unless you have some Captain Insano hard drive setup. Even 15k drives top out in the 50-70 MB/sec range, so you'd need 2-3 transferring at the SAME TIME for SCSI 160 to be limiting things.

RAID 5 is completely scalable. It can easily reach speeds of 3GB/sec with enough drives.

 

[imported_Kensai]

Originally posted by: V00D00

Originally posted by: Concillian
A normal 32bit/33MHz PCI slot like is on just about every desktop board made is 133MB/sec

Also PCI bus is shared so if you have anything else on the PCI bus (IDE, netowrk) it needs to share that 133MB/sec.

For SCSI cards it doesn't make sense to get more than a SCSI 160 board unless you have some Captain Insano hard drive setup. Even 15k drives top out in the 50-70 MB/sec range, so you'd need 2-3 transferring at the SAME TIME for SCSI 160 to be limiting things.

RAID 5 is completely scalable. It can easily reach speeds of 3GB/sec with enough drives.

Don't forget about two RAID 5 arrays in a RAID 0 array. (Raid 50) That breaks it. 😉

 

[Crusty]

Why bother with that many drives? 2 15k Hitachi drives in raid 0 will max out a 32-bit/33mhz bus.

 

[ShadowBlade]

thx V00D00

 

[Concillian]

Originally posted by: V00D00

Originally posted by: Concillian
it doesn't make sense to get more than a SCSI 160 board unless you have some Captain Insano hard drive setup.

RAID 5 is completely scalable. It can easily reach speeds of 3GB/sec with enough drives.

While I don't think I'd use the word 'easily', I don't disagree and never said anything to the contrary of that. I thought I had covered situations like that because I do believe that would be a 'Captain Insano hard drive setup'. Especially for an end user.