Tekram Technology DC-390 Series, User Manual, Page: 68 / 71

C. General Troubleshooting Tips
DC-390 Series User’s Manual
68 68
•
DC-390: PCI SCSI controller based on AMD 53C974A (SCSI core is 53CF94)
•
DC-300B: ISA SCSI controller based on NCR 53CF94
•
IN-9100: PCI SCSI controller by INITIO, based on PCI bus master controller and
53CF94
Procedures for correcting this problem:
1.
Set "Parity Checking" for all IDs to "No" in "Set Devices Options" setup menu (*
recommended *). Or
2. Set "Allow Disconnection" for the ID corresponding to RO-1420C to "No" in the "Set
Devices Options" setup menu. (This method may affect the overall SCSI bus
performance).
The following controllers do not exhibit this problem when combined with the RO-1420C,
since their associated SCSI cores IGNORE any SCSI parity error during the SCSI reselection
phase.
•
AHA-2940: Adaptec PCI SCSI controller
•
DC-390U/F: PCI Ultra/Wide SCSI controller by TEKRAM based on 53C875
12. Linux/FreeBSD/Unix-based drivers: They
are available under “Driver&AP”
section of each model under “Storage” section on FTP site ( ftp://ftp.tekram.com.tw ).
13. Overclocking policy:
The difference between SCSI chip and CPU is that CPU will pack 100MHz if it can
run 100MHz and 66MHz if can run 66MHz during production. It is a natural
phenomena that some chips can run higher speed and others can
’ t do so in
production process. There is a yield rate problem for the same batch of chips. The
trivial in manufacturing process will make a difference in working frequency for
different chips. Even a different location on the same wafer (in the middle or on the
side) of chips will cause a different yield rate and working frequency.
The production and packing process of SCSI chips doesn ’ t have operating
frequency testing procedures as CPUs
’
to filter SCSI chip. They pass test only if they
can run 33MHz or above and are packed. That ’ s why some SCSI chips can be
overclocked and others can
’
t. It can
’
t be differentiated from the package. The
33MHz PCI clock is transmitted from motherboard to PCI slot and then to SCSI chip
of PCI card. So, the PCI interface related circuit inside SCSI chip is relevant to PCI
clock. As to 40MHz OSC on SCSI card, it is used for SCSI Core Logics only inside
SCSI chip. PCI Interface related circuit would not use this 40MHz. The circuit of
SCSI Core Logics only uses 40MHz provided by OSC. It is irrelevant to PCI clock.