Riser assembly and computing system

A compact expansion card riser assembly for connection of two expansion cards to horizontally oriented circuit board is disclosed. The riser assembly includes a support bracket, a first horizontal riser board, and a second horizontal riser board. The first horizontal riser board has a first expansion card connector. The first horizontal riser board is attached to the support bracket. The support bracket and first horizontal riser board support a horizontally oriented expansion card. The second horizontal riser board has a second expansion card connector. The second horizontal riser is attached to the support bracket. The support bracket and second horizontal riser board support a horizontally oriented expansion card.