[7315] in linux-scsi channel archive
DC-3x5 .vs. DC-390/U/F
daemon@ATHENA.MIT.EDU (Gerard Roudier)
Sun Oct 3 10:03:10 1999
Date: Sun, 3 Oct 1999 16:14:59 +0200 (MET DST)
From: Gerard Roudier <groudier@club-internet.fr>
To: linux-scsi@vger.rutgers.edu, ncr53c810@colorado.edu
cc: erich@tekram.com.tw
Message-ID: <Pine.LNX.3.95.991003161226.1502C-100000@localhost>
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Hello,
We have received a report for a Linux user who owns a Tekram
DC315 board and who failed to install a Linux distribution.
This people had been confused by the controller name and
thought the ncr/sym drivers supported the board.
In fact the Tekram DC-3x5 series of PCI-SCSI adapters donnot
use LSI/SYMBIOS 53C8XX chips, but a Tekram proprietary chip,
they named S1040.
This chip is very different from the 53C8XX family and needs
different drivers. Tekram provides some drivers for their
DC-3x5 controllers from their ftp site.
People who want Tekram boards that use 53C8XX chips must not
purchase these new boards, but order one of the following:
DC-310, DC-390-U, DC-390-F, DC-390-U2B, DC-390-U2W that are
excellent products.
I have looked into Tekram driver sources for the S1040 chip, and
it seems that this chip does not implement a hardware phase engine.
That means that all phase changes must be handled from the C
code. May-be, it is their driver that is not optimal, may-be
the S1040 chip is actually designed so.
Result is:
- At least 5 interrupts per SCSI transfer (instead of about 1 with
53C8XX family and aic7xxx family that implement a hardware phase
engine)
- Far more IOs from the C code per SCSI transfer.
- More CPU load per SCSI transfer.
On the comparison chart which is available at their Web site, they
announce for the DC-3X5 family about the same performance as the
boards using a 53C8XX chip. Some of the number are a bit better for
the DC-3X5 family.
Based on simple and obvious technical considerations, and if the
S1040 chip does not implement a hardware phase engine, then it is
obvious to me that this comparison chart is not serious or based on
silly benchmaks performed on a poor O/S that does not deserve to be
used for this purpose. It would be kind from Tekram to reply to
my posting or to _actually_ explain the _real_ differences between
their PCI-SCSI controller families. Having a product naming that
avoid confusing users would be a plus.
Gérard.
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