Yamaha CD Recordable/Rewritable Drive CRW-70 - Manual (Page 17)

Features of the CRW-70 Drive
8
Test writing for Buffer Underrun
Test writing is a function to check for the likely occurrence of Buffer Underrun
on your computer system.
The CD writing software that came with the CRW-70 drive includes test
writing functions for this purpose.
When Buffer Underrun Protection is activated (Default), test writing cannot be
selected on your writing software.
To use test writing, Buffer Underrun Protection should be deactivated.