Datasheet
Page 7
... When stacking the DGS-3130-54TS/54S/54PS models, the stacking cost is 9. For example: 2 x DGS-3130-30TS (2 stacking cost) + 2 x DGS-3130-30S (2 stacking cost) + 4 x DGS-3130-54TS (8 stacking cost) consumes a total stacking cost of D-Link Corporation or its ...Link Reseller. The maximum units per stack is 2 per unit. When stacking different models in the same stack, switches can be stacked up to speed are the property of 12 stacking cost per unit. The maximum units per stack is 1 per stack. UPDATED 17-SEP-2018 (SMO) HARDWARE REV A DGS-3130-SERIES_REVA_DATASHEET_1.01_EN_US.PDF...
... When stacking the DGS-3130-54TS/54S/54PS models, the stacking cost is 9. For example: 2 x DGS-3130-30TS (2 stacking cost) + 2 x DGS-3130-30S (2 stacking cost) + 4 x DGS-3130-54TS (8 stacking cost) consumes a total stacking cost of D-Link Corporation or its ...Link Reseller. The maximum units per stack is 2 per unit. When stacking different models in the same stack, switches can be stacked up to speed are the property of 12 stacking cost per unit. The maximum units per stack is 1 per stack. UPDATED 17-SEP-2018 (SMO) HARDWARE REV A DGS-3130-SERIES_REVA_DATASHEET_1.01_EN_US.PDF...