transfer rate negotiation

[Metod Kozelj]

Hello,

I'm writing this mail not as a complaint, but rather my own curiosity.

In one of my Linux/Alpha boxes I have AHA-2940UW and Seagate ST39175LW
hard disk. The /proc/scsi/aic7xxx/0 says

  Device using Wide/Sync transfers at 20.0 MByte/sec, offset 8
  Transinfo settings: current(25/8/1/0), goal(25/8/1/0), user(25/15/1/0)

I now wonder shouldn't it be 40.0 MByte/sec. Specification for AHA-2940UW
says it's capable of 40MBytes/sec and specification for ST39175LW says
just the same (40MBytes/sec in SCSI2 mode, 80MBytes/sec in LVD mode).
As the internal transfer rate for that drive is specified to be up to 240
Mbits/sec (which is more than 20 MBytes/sec), I think drive could use
higher transfer rate sometimes.

Quite simillar situation is with my other drive in the same box. It is
Seagate ST34572N, specified to be capable of 20MBytes/sec. However, it
only runs at 10MBytes/sec:

  Device using Narrow/Sync transfers at 10.0 MByte/sec, offset 15
  Transinfo settings: current(25/15/0/0), goal(25/15/0/0), user(25/15/1/0)

They are on different cables (ST39175LW is on actively-terminated
68-pin wide bus and ST34572N is on 50-pin narrow bus; terminated using
on-drive termination) so they shouldn't interfere, should they?

Now, as I'm using the controler on Alpha, I can't go into SCSI BIOS (using
CTRL-A) to check the settings. I'm quite sure that when the board was
placed into the machine, it was brand new with default settings.

Any ideas?

Regards,
  Metod

Metod Kozelj

mailto:Metod.Kozelj at rzs-hm.si            /\  Ne posiljajte mi smeti ker grizem!
http://www.rzs-hm.si/                   /  \  Don't spam me for I bite!
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---- perl -e 'print $i=pack(c5,(41*2),sqrt(7056),(unpack(c,H)-2),oct(115),10);'




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