Systems containing multiple graphics-processing-unit (GPU) clusters are difficult to use for real-time electroholography when using only a single spatial light modulator because the transfer of the computer-generated hologram data between the GPUs is bottlenecked. To overcome this bottleneck, we propose a rapid GPU packing scheme that significantly reduces the volume of the required data transfer. The proposed method uses a multi-GPU cluster system connected with a cost-effective gigabit Ethernet network. In tests, we achieved real-time electroholography of a three-dimensional (3D) video presenting a point-cloud 3D object made up of approximately 200,000 points.