A computer data signal comprises a first code group and a second code group. The first code group has a first symbol and an error detection code for the first symbol. The second code group has a second symbol and an error correction code. The error correction code provides error correction for a third symbol that includes the first symbol and the second symbol.
To store N bits of M.gtoreq.2 logical pages, the bits are interleaved and the interleaved bits are programmed to .left brkt-top.N/M.right brkt-bot. memory cells, M bits per cell. Preferably, the interleaving puts the same number of bits from each logical page into each bit-page of the .left brkt-top.N/M.right brkt-bot. cells. When the bits are read from the cells, the bits are de-interleaved. The interleaving may be deterministic or random, and may be effected by software or by dedicated hardware.
Determining an error-correcting code (ECC) for a cache entry based at least on the data stored in the cache entry and the memory address at which the data is permanently stored is disclosed. A cache entry for a desired memory address is retrieved. The cache entry includes data and a stored ECC based on the data and a memory address. An ECC is determined based at least on the data of the cache entry and the desired memory address. If the ECC at least based on the cache entry data and the desired memory address equals the stored ECC, then the cache entry caches the desired memory address without error.
Determining an error-correcting code (ECC) for a cache entry based at least on the data stored in the cache entry and the memory address at which the data is permanently stored is disclosed. A cache entry for a desired memory address is retrieved. The cache entry includes data and a stored ECC based on the data and a memory address. An ECC is determined based at least on the data of the cache entry and the desired memory address. If the ECC at least based on the cache entry data and the desired memory address equals the stored ECC, then the cache entry caches the desired memory address without error.
The retrieval of all tag entries of cache locations for a memory address is disclosed, as well as the determining of an error correcting code (ECC) for the tag entries based thereon. Tag entries of tag memory that correspond to possible cache locations within an n-way associative cache are retrieved for a memory address. An ECC for the tag entries, based on the entries, is determined, and is stored as part of the entries within the tag memory. The n-way associative cache may be a two-way associative cache, such that there are two tag entries corresponding to two possible cache locations within the cache for the memory address. The ECC for the two tag entries are thus based on the two tag entries.
A memory control device includes a writing unit writing information to a memory module, a reading unit reading the information from the memory module, an error detecting unit executing a detection of an error in the formation in parallel with the reading operation by the reading unit, an error correcting unit correcting the error in the information containing the error detected, and a control unit controlling a transfer and a receipt of the information to and from an external device and stopping, when the error is detected, an output of the information to the external device.
