Memory Option # Manufacturing Part # Description Previous Part # X7402A [S] 512MB DDR Memory Option (2 × 256MB DIMMs) 370-5565 19 [F] 256MB Registered DDR DIMM (SPD 0.0) n/a X7403A [S] 1GB DDR Memory Option (2 × 512MB DIMMs) 370-4939 20 [F] 512MB Registered DDR DIMM (SPD 0.0) n/a X7404A [S] 2GB DDR Memory Option (2 × 1GB DIMMs) 370-4940 21 [F] 1GB Registered DDR DIMM (SPD 0.0) n/a X7602A [S] 512MB DDR Memory Option, SPD 1.0 (2 × 256MB DIMMs) 370-6201 256MB Registered DDR DIMM (SPD 1.0) n/a X7603A [S] 1GB DDR Memory Option, SPD 1.0 (2 × 512MB DIMMs) 370-6202 512MB Registered DDR DIMM (SPD 1.0) n/a X7604A [S] 2GB DDR Memory Option, SPD 1.0 (2 × 1GB DIMMs) 370-6203 1GB Registered DDR DIMM (SPD 1.0) n/a X7702A [S] 512MB DDR Memory Option, SPD 0.0 or 1.0 (2 × 256MB DIMMs) 370-7680 256MB Registered DDR DIMM (SPD 0.0 or 1.0) PC2100 & faster n/a