A recent update to the DDR memory for the SLX 9540 may cause the device to fail to boot up properly, if it is downgraded to images without support for the newer memory parameters.
Newer hardware revision of SLX 9540, HW Rev 84-xxxxxx-10 and above as shown in the “show chassis” output, have a new DDR memory installed which may require additional tuning parameters available only in newer releases. The “show chassis” command must be run prior to attempting a downgrade. Downgrading a newer hardware revision of SLX 9540 to an unsupported version of software, which does not have the appropriate tuning parameters for the new memory, will cause the SLX 9540 to panic on bootup. The SLX 9540 will show: "ERROR: Assertion failed" during bootup after firmware downgrade.
Show chassis example:
SLX# show chassis
Chassis Name: BR-SLX9540
CHASSIS/WWN Unit: 1
Power Consume Factor: 0
Factory Part Num: 84-1003120-10
Factory Serial Num: FDK3803Q016
Manufacture: Day: 13 Month: 1 Year: 2023
Update: Day: 29 Month: 1 Year: 2023
Time Alive: 3 days
Time Awake: 0 days
Below console log on bootup identifies FRU ID 8 in the older versions of the OS which indicates the newer DDR is installed.
setting_DDR_type_dram_type_DDR4_MICRON_Y4016AABG_JD_F_ 4GBIT for FUSION AVALANCHE SW_FRU_ID=8
The device will not boot properly and will continuously error out in a boot loop.
SLX 9540 Hardware With Hardware rev 84 and later.
All SLX-OS releases prior to the following patches: SLX-OS 20.3.2g, 20.3.4d, 20.4.1d, or 20.4.2
SLX stuck in continuous boot loop
SLX was downgraded from 20.x firmware to 18r.x firmware
After downgrade, console message shows the following: ERROR: Assertion failed: (0) at /vobs/projects/2022/11/09-16:53:53, [HASM-1200], 21, FFDC, WAR
hslagtd process panicked
To recover a device in a boot loop, upgrade the device software using NETINSTALL. The OS will need to be reinstalled from USB or the Network.
It is advisable to upgrade to SLXOS 20.3.2g, 20.3.4d, 20.4.1d, or 20.4.2 and later to eliminate the potential issue with the device not booting properly. The new tuning parameters available for the newer DDR memory are in the releases above only.
Please see the full field notice article here for more details.