On Sun, Oct 03, 1999 at 04:14:59PM +0200, Gerard Roudier wrote:
> 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.
True.
> 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.
True. It does not have something like a script processor or similar. It does
invoke an interrupt every time the SCSI phase changes.
The design is similar to the AM53C974 chip plus a few extras like Scatter
Gather hardware support.
BTW: You can find a driver on ftp:://ftp.suse.com/pub/people/garloff/linux/dc395/
> 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.
If you use an OS that does have to do other things while waiting for I/O, it
does not make a difference. Even on Linux, the difference to those adapters
implementing script processors is quite small, unless your I/O load gets very
high.
> 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.
Regards,
--
Kurt Garloff <[EMAIL PROTECTED]> Wuppertal, FRG
PGP2 key: See mail header, key servers Linux kernel development
SuSE GmbH, N�rnberg, FRG SCSI drivers: tmscsim(DC390), DC395
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