Rajko M. wrote:
On Monday 07 May 2007 09:43, Sid Boyce wrote:
Rajko M. wrote:
...
The speed test
hdparm -t /dev/hda
shows speed of 55 MB/s for ATA 100 drive, which seems to be right. For
details on transfer rates
http://www.realworldtech.com/page.cfm?ArticleID=RWT011701000000
The difference between 16 and 32 transfer is non existent on older
machine, both show 55 MB/s. The reason is probably oldfashioned parallel
cable that has 16 lines for data transfer and using 32 bit brings no
improvement, except on very old systems where CPU load is 1/2 if it can
send 32 bits to controller at once.
I did mention this to Donn in a private email, then we got into the
subject of the difference between cables.
OFF TOPIC:- One thing I read said, in order to minimise crosstalk, that
all 80 wires are connected at the blue end, but 40 connect to the grey
connector, the other 40 go to the black connector. However, trying to
verify it using a DVM, I got shorts registered on the same pins on both
the grey and the black connectors. One suggestion from Donn is that
they use 40 pins and 40 earths commoned up at the blue (motherboard)
end. This seems likely as shorts on a number of pins can be measured on
the connectors, though I haven't done enough to verify how they are
distributed. Then there is the connundrum as to how the whole thing
looks electrically when connected to devices and a motherboard.
Regards
Sid.
Grounds commoned on motherboard side will show shorts on the other end too.
Wires are to short to see 2 wire lengths resistance with DMV, so it will
appear as short on both ends. They had to use existing ground pins on 40 pins
connector and they needed 40 extra wires between existing signal wires to
prevent crosstalk. More:
http://en.wikipedia.org/wiki/Advanced_Technology_Attachment
I never tried to find out exact reasons for the one side grounding.
Thanks for the URL, excellent description.
Regards
Sid.
--
Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
Specialist, Cricket Coach
Microsoft Windows Free Zone - Linux used for all Computing Tasks
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
