Described is a programmable logic device (PLD) with columns of DSP slices that can be combined to create DSP circuits of varying size and complexity. DSP slices in accordance with some embodiments includes programmable operand input registers that can be configured to introduce different amounts of delay, from zero to two clock cycles, for example, to support pipelining. In one such embodiment, each DSP slice includes a partial-product generator having a multiplier port, a multiplicand port, and a product port. The multiplier and multiplicand ports connect to the operand input port via respective first and second operand input registers, each of which is capable of introducing from zero to two clock cycles of delay. In another embodiment, the output of at least one operand input register can connect to the input of an operand input register of a downstream DSP slice so that operands can be transferred among one or more slices.