the line size of instruction cache of NiosII?

Yes.

From the Nios II Processor Reference Handbook pg 15-5:

<div class='quotetop'>QUOTE </div>

--- Quote Start ---

Instruction Cache

The instruction cache memory has the following characteristics:

* Direct-mapped cache implementation

* Critical word first

* 32 bytes (8 words) per cache line[/b]

--- Quote End ---

Dennis Scott

Microtronix Datacom Ltd.