GeForce3 with 128bit/256bit DDR Memory Interface
2001.02.25

There are speculations whether NVIDIA will incorporate a 256bit DDR memory interface on the GeForce3 that will be released in a few days. Though there has been potent evidence that GeForce3 will support 256bit DDR memory interface, the most probable way is 128bit version of GeForce3 will come out first and then there will be 256bit version a few months later, just as the cases of GeForce256 SDR and GeForce256 DDR.

As is showed in Table 1, there are more than 200 extra pins on the GeForce3 chip comparing with that of a GeForce2 chip. According to this, there has been inference indicated that 256bit DDR memory interface is incorporated on the GeForce3. The quotes below show the clue.

http://boards.fool.com/Message.asp?mid=12069845&sort=threaded (2000.02.28)
"If everyone (even the pro-nVidia reviewers) recognizes that GeForce is bottlenecked by memory bandwidth, why isn't the solution to go to a 256-bit bus or add a second 128-bit bus (eg: to separate texture data from T&L data) rather than relying only on DDR and higher RAM speeds with the single 128-bit bus and unified memory architecture?"

http://boards.fool.com/Message.asp?mid=12076523 (2000.02.29)
"I think the main issue is cost of the additional pins on the bus. To add an extra 128 data pins you also need a large number of additional ground pins (probably more than 128.) The IO pads on a chip which connect it to the device pins require a lot of power in comparison to the rest of the chip and also occupy a significant area on the die, so doubling the bus width will have an impact on power and thermal issues. The additional pins also cause the device package to be a lot larger which has other impacts.

You also have the issue of all those extra traces to be routed on the card itself and the requirement for wider memory (i.e. more chips) to support the doubled bus width. The board issues are encountered and addressed on the V5 without having to solve the on-chip problems and costs."

http://boards.fool.com/Message.asp?mid=12476511 (2000.04.27)
"If you're going to have 64MB or more RAM on a video card anyway, why not address it over a 256-bit bus? I can see a challenge in the routing density on the circuit board under the graphics chip. This could force a move to a (slightly more expensive to manufacture, but extremely well-established technology) 6-layer printed circuit board instead of a (cheaper) 4-layer card. (Are the newer monster graphics chips already in PGA, or are they still using a quad package? I'd guess that the increased pinout would require a large PGA package. (For example, Socket-A is what, almost 500 pins?))"

http://www.nvnews.net/articles/loyd_case_interview/page_2.shtml (2000.06.29)
"nV News: Will NVIDIA ever incorporate a 256-bit DDRAM memory interface?
Loyd (NVIDIA): While I wouldn't preclude anything, the number of pins you'd have to add to any chip for that kind of interface would raise the packaging costs substantially."

http://www.hardocp.com/ (2001.02.23 Morning Ed II)
"Ok, this isn't news, just some personal observation from a Computer Engineer. With the recent unveiling of the GF3 they put a pic of the chip which shows how much balls it has. (Talking BGA balls here). I scaled up the picture and counted 700. If you recall the GF2, it had 532 balls (I counted to compare GTS with Ultra pics to dismiss 256bit for Ultra a while back). Take the difference (168 for the math impaired), subtract 128 and you end up with 40 extra balls for signal integrity (power/gnd) which is required as your ball count grows.

Wallah! 256bit DDR memory interface on GeForce3 for 2X the bandwidth of GeForce2.  I had my doubts, but this one could be a screamer. I'm impressed! I might have to actually buy one after never owning an NVidia based product. "

Table 1. Pins on the NVIDIA Video Chip

Video Chip		Pins on the Chip	Total pins
GeForce3			700
GeForce2			492
GeForce256			548

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