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To: Dan3 who wrote (28788)	9/6/1999 2:02:00 PM
From: John Walliker	Read Replies (1) \| Respond to of 93625

Dan3, I looked at the Samsung web site as you suggested and downloaded the data sheets for 256 Mbit sdram and 128/144 Mbit RDRAM. You are assuming that both are made on the latest process which may well be true. I could find no data for die sizes, so we are both guessing. My guess goes as follows: 128 and 144 Mbit RDRAM is in a uBGA package meaasuring 12.0 x 10.2 mm. Assume 0.5 mm clearance at each edge to give a maximum die size of 11 x 9.2 mm. This corresponds (for the 144 M parts) to a density of 144/(11 x 9.2) = 1.42 Mbit/sq mm. 256 Mbit SDRAM is packaged in a long and thin TSOP package with a body (excluding the leads) of 10.16 mm width. Assume 1 mm clearance at each side due to the different packaging technology and a 2:1 aspect ratio for the die. This gives a density of 256/(8.16 x 16.32) = 1.92 Mbit/sq mm. The ratio between these is 1.35 - quite close to the 30% overhead that has been widely quoted for RDRAM versus SDRAM. Now please tell me why you think SDRAM has twice the density of RDRAM. I am sure somebody will appear to correct me if any of my assumptions is wrong:-) John