nRF51822_xxaa SDK12 S130 v2.0.1 IROM and IRAM settings

We have a custom board with the nRF51822 xxaa chip on it. The board is completely functional and uses SDK8.0 and S110 as of now. We are porting the firmware to SDK12 and S130 SD. Following this blog [https://devzone.nordicsemi.com/blogs/723/rom-and-ram-management/], we tried the values of IROM and IRAM as follows in experimental_ble_app_blinky. The board doesn't show any signs of BLE advertising. Below are the IRAM and IRAM values that were used.

IRAM base - 0x20001870 IRAM size(16 kB RAM) - 0x2790

IROM base - 0x1B000 IROM size(256 kB Flash) - 0x25000

We also tried exprimental_ble_app_blinky from SDK11 with the above IROM and IRAM settings and it didn't work. But, when the below settings were tried, BLE started advertising.

IRAM base - 0x20002000 IRAM size(16 kB RAM) - 0x2000

IROM base - 0x1B000 IROM size(256 kB Flash) - 0x25000

We tried the same settings on SDK12 experimental_ble_app_binky and the board doesn't advertise.

If someone could get back to me with the IROM and IRAM settings for nRF51822 xxAA chip for SDK12 and SD S130 v2.0.1, it would be really helpful.

I also want to understand why 0x20001870 didn't work, while 0x20002000 worked on SDK11.