An aspect includes a system architecture that includes a processing unit, an accelerator, a main source buffer, a main target buffer, and a memory block. The main source buffer stores a first part of a source symbol received from an external source. The main target buffer stores an output symbol received from the accelerator. The memory block includes an overflow source buffer that stores the first part of the source symbol received from the main source buffer. The accelerator fetches the first part of the source symbol stored in the overflow source buffer and a second part of the source symbol stored in the main source buffer, and converts the first and second parts of the source symbol together into the output symbol. The second part of the source symbol includes a part of the source symbol not included in the first part of the source symbol.