Re: Cheetah vs. UDMA: Bonnie says UDMA is faster! why?
Geert Uytterhoeven (Geert.Uytterhoeven@cs.kuleuven.ac.be)
Wed, 25 Mar 1998 17:50:08 +0100 (CET)
On Wed, 25 Mar 1998, Mark Lehrer wrote:
> ncr53c875-0-<0,0>: SLOW WIDE SCSI 10.0 MB/s (200 ns, offset 15)
^^^^^^^^^
> SCSI device sda: hdwr sector= 512 bytes. Sectors= 8887200 [4339 MB] [4.3 GB]
>
> --------
>
> Kernel config NCR section:
>
> NCR53C8XX SCSI support (CONFIG_SCSI_NCR53C8XX) [Y/n/?]
> detect and read serial NVRAMs (CONFIG_SCSI_NCR53C8XX_NVRAM_DETECT) [N/y/?]
> enable tagged command queueing (CONFIG_SCSI_NCR53C8XX_TAGGED_QUEUE) [Y/n/?]
> use normal IO (CONFIG_SCSI_NCR53C8XX_IOMAPPED) [N/y/?]
> maximum number of queued commands (CONFIG_SCSI_NCR53C8XX_MAX_TAGS) [4]
> synchronous transfers frequency in MHz (CONFIG_SCSI_NCR53C8XX_SYNC) [5]
^
Since you selected a maximum synchronous transfer frequency of 5 MHz, the
maximun transfer speed is indeed limited to 10 MB/s (16 bit times 5 MHz).
To get Ultra-SCSI speeds, you have to select 20 MHz.
Disclaimer: I don't have a NCR53c875 and I don't know whether the driver
supports 20 MHz.
Greetings,
Geert
--
Geert Uytterhoeven Geert.Uytterhoeven@cs.kuleuven.ac.be
Wavelets, Linux/{m68k~Amiga,PPC~CHRP} http://www.cs.kuleuven.ac.be/~geert/
Department of Computer Science -- Katholieke Universiteit Leuven -- Belgium
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