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. -- Regards, Rajko. --------------------------------------------------------------------- To unsubscribe, e-mail: opensuse-factory+unsubscribe@opensuse.org For additional commands, e-mail: opensuse-factory+help@opensuse.org