Hello,
excuse my (old) question, but I have a big problem with kernel 2.4.21-4.EL
and SMP+SCSI (Red Hat), in a critical running server.

Trying to boot the server with SMP version (2.4.21-4.ELsmp)
the system sleep over "SCSI DAT detect".

This is the report of dmesg in NOT SMP version:
---------------------------------
[..]
PCI: Enabling device 03:0c.0 (0000 -> 0003)
scsi2 : Adaptec AIC79XX PCI-X SCSI HBA DRIVER, Rev 1.3.10
<Adaptec 29320LP Ultra320 SCSI adapter>
aic7901A: Ultra320 Wide Channel A, SCSI Id=7, PCI-X 67-100Mhz, 512 SCBs

Starting timer : 0 0
blk: queue f6d3dc14, I/O limit 4095Mb (mask 0xffffffff)
(scsi2:A:6): 80.000MB/s transfers (40.000MHz, 16bit)
Vendor: IBM Model: DDS Gen5 Rev: A060
Type: Sequential-Access ANSI SCSI revision: 03
Starting timer : 0 0
blk: queue f6d3de14, I/O limit 4095Mb (mask 0xffffffff)
Journalled Block Device driver loaded
kjournald starting. Commit interval 5 seconds
EXT3-fs: mounted filesystem with ordered data mode.
Freeing unused kernel memory: 164k freed
usb.c: registered new driver usbdevfs
usb.c: registered new driver hub
usb-uhci.c: $Revision: 1.275 $ time 18:21:59 Oct 3 2003
usb-uhci.c: High bandwidth mode enabled
PCI: Setting latency timer of device 00:1d.0 to 64
usb-uhci.c: USB UHCI at I/O 0x2200, IRQ 5
usb-uhci.c: Detected 2 ports
usb.c: new USB bus registered, assigned bus number 1
[..]
---------------------------------


With SMP boot, the system stops its startup with:
---------------------------------
[..]
PCI: Enabling device 03:0c.0 (0000 -> 0003)
scsi2 : Adaptec AIC79XX PCI-X SCSI HBA DRIVER, Rev 1.3.10
<Adaptec 29320LP Ultra320 SCSI adapter>
aic7901A: Ultra320 Wide Channel A, SCSI Id=7, PCI-X 67-100Mhz, 512 SCBs

Starting timer : 0 0
blk: queue f6d3dc14, I/O limit 4095Mb (mask 0xffffffff)
---------------------------------


Looking around this problems someone wrote:

...Dumping the ahd state when probing the da and simply stopped.
So I set the SCSI BIOS to restrict the device speed upto 80MB/s and
the problem went away.
After that, the machine runs flawlessly for 8 months.


Can You help me?

Best Regards

---
Sim