If the board returns correct data when taking single samples but fails to operate satisfactorily when acquiring data at a programmed rate, there is probaby an interrupt or DMA channel conflict. The single sample mode does not require the use of an interrupt or DMA transfer. When a pacer clock is used to control the rate at which data are acquired, the IRQ and/or DMA are necessary to coordinate these transfers. Sound cards often present DMA conflicts. Network or even video cards often conflict with interrupt settings.