Dell OptiPlex 990 (Early 2011) - Manual (Page 85)

Cards
Mini-Tower up to one full-height card
Desktop up to one low-profile card
Small Form Factor none
Ultra Small Form Factor none
PCI Express x1
Mini-Tower up to three full-height cards
Desktop up to three low-profile cards
Small Form Factor up to two low-profile cards
Ultra Small Form Factor none
PCI-Express x16
Mini-Tower up to two full-height cards
Desktop up to two low-profile cards
Small Form Factor up to two low-profile cards
Ultra Small Form Factor none
Mini PCI Express
Mini-Tower none
Desktop none
Small Form Factor none
Ultra Small Form Factor up to one half-height card
Drives
Externally Accessible (5.25–inch drive bays)
Mini-Tower two
Desktop one
Small Form Factor one slim optical drive bay
Ultra Small Form Factor one slim optical drive bay
Internally Accessible:
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