[7324] in linux-scsi channel archive
Re: DC-3x5 .vs. DC-390/U/F
daemon@ATHENA.MIT.EDU (Kurt Garloff)
Tue Oct 5 16:52:40 1999
Date: Tue, 5 Oct 1999 22:09:23 +0200
From: Kurt Garloff <garloff@suse.de>
To: Gerard Roudier <groudier@club-internet.fr>
Cc: linux-scsi@vger.rutgers.edu, ncr53c810@colorado.edu,
erich@tekram.com.tw
Message-ID: <19991005220923.B1135@kurt.kdt.de>
Mail-Followup-To: Gerard Roudier <groudier@club-internet.fr>,
linux-scsi@vger.rutgers.edu, ncr53c810@colorado.edu,
erich@tekram.com.tw
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In-Reply-To: <Pine.LNX.3.95.991003161226.1502C-100000@localhost>; from Gerard Roudier on Sun, Oct 03, 1999 at 04:14:59PM +0200
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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=20
> use LSI/SYMBIOS 53C8XX chips, but a Tekram proprietary chip,=20
> they named S1040.
>=20
> This chip is very different from the 53C8XX family and needs=20
> different drivers. Tekram provides some drivers for their=20
> DC-3x5 controllers from their ftp site.
>=20
> People who want Tekram boards that use 53C8XX chips must not=20
> 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=20
> excellent products.
True.
> I have looked into Tekram driver sources for the S1040 chip, and=20
> it seems that this chip does not implement a hardware phase engine.
>
> That means that all phase changes must be handled from the C=20
> code. May-be, it is their driver that is not optimal, may-be=20
> the S1040 chip is actually designed so.
> Result is:
> - At least 5 interrupts per SCSI transfer (instead of about 1 with=20
> 53C8XX family and aic7xxx family that implement a hardware phase=20
> 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=20
> announce for the DC-3X5 family about the same performance as the=20
> boards using a 53C8XX chip. Some of the number are a bit better for=20
> 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 ve=
ry
high.
> Based on simple and obvious technical considerations, and if the=20
> S1040 chip does not implement a hardware phase engine, then it is=20
> obvious to me that this comparison chart is not serious or based on=20
> silly benchmaks performed on a poor O/S that does not deserve to be=20
> used for this purpose. It would be kind from Tekram to reply to=20
> my posting or to _actually_ explain the _real_ differences between=20
> their PCI-SCSI controller families. Having a product naming that=20
> avoid confusing users would be a plus.
Regards,
--=20
Kurt Garloff <garloff@suse.de> Wuppertal, FRG
PGP2 key: See mail header, key servers Linux kernel development
SuSE GmbH, N=FCrnberg, FRG SCSI drivers: tmscsim(DC390), DC395
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