A computerized system is booted from a flash memory device configured to always operate one or more of its blocks only in a M-bit-per-cell mode and the rest of its blocks in a N>M-bit-per-cell mode. When the system is powered up, an initialization program is retrieved from the M-bit-per-cell block(s), corrected for errors using a first error correction method, and executed. Data accessed subsequently from the N-bit-per-cell blocks are corrected using an error correction method that corrects more errors per block than the first error correction method.