A hard disk unit includes a disk, a controller microprocessor, a host businterface, a buffer memory, a buffer memory controller, and a disk formatter.The bus interface receives write operations, and the buffer memory controllerstores the corresponding write operation data in the buffer memory in therelative order in which the operations are received. The buffer memorycontroller subsequently transfers the data of a write operation from thebuffer memory to the disk formatter, which formats the data and writes it tothe disk. The buffer memory controller controls read and write access to thebuffer memory. The buffer memory controller includes a set of addressregisters and a set of block count registers. The microprocessor loads theaddress registers with the addresses within the buffer memory of the data oftwo or more write operations. The microprocessor loads the block countregisters with the size, in blocks, of the corresponding operations. Themicroprocessor then issues a single command to the buffer memory controller totransfer the data identified by the address registers and block countregisters from the buffer memory to the disk formatter. The address registersand block count registers enable the buffer memory controller to transfer thedata of several write operations in any order. Previous buffer controllers aretypically capable of transferring the data of several write operations only inthe same order in which the data is stored in the buffer memory.
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