[TriLUG] OT: hd speed with 33MHz and 100MHz controller are the same

Joseph Mack NA3T jmack at wm7d.net
Tue Jun 12 14:07:07 EDT 2007


I have an old (200MHz dual Pentium Pro) computer with (I 
think) a 33MHz PCI bus (have no idea really).

I have two disks -

o original onboard disk controller connected to a 40G IDE 
disk (several years old) via and old style IDE ribbon

o a 100MHz Promise controller in a PCI card connected to a 
new disk (bought yesterday) via one of the new style (twice 
as many wires) ribbon cables.

I would have expected the new disk with the 100MHz 
controller to be much faster, but it appears to be the same 
speed as the older disk with the slower controller.

My test is badblocks, which I'm running on both disks at the 
same time. Both disks are writing the same number of 
blocks/time (within a couple of 5). I get the same speed I 
move the disk on the PCI bus to an external USB 2.0 
enclosure attached to a USB 2.0 PCI controller.

with hdparm

# hdparm /dev/foo

I get the same output for all devices (eg using_dma is on).

Have I set it up the faster disk controller wrong, or is the 
slow 33MHz PCI bus determining the speed?

(I would expect that badblocks doesn't send much over the 
PCI bus and it's all done by talking between the disk 
controller and the disk, but the load average is about 4 for 
2 disks, so I guess the CPU is at least waiting for the 
disk, if not doing something itself).

Thanks Joe

-- 
Joseph Mack NA3T EME(B,D), FM05lw North Carolina
jmack (at) wm7d (dot) net - azimuthal equidistant map
generator at http://www.wm7d.net/azproj.shtml
Homepage http://www.austintek.com/ It's GNU/Linux!



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