Currently, NVIDIA only has 16, 32 and 64MB TurboCache products on the market while ATI has a 32 and a 128MB configuration in their HyperMemory products. You can see my recent review of them here. Well it looks like this summer NVIDIA might be launching a 128MB version of their TC product.
Nvidia plans to introduce a new version of its GeForce 6200 with TurboCache that includes 128MB of on-board memory for the mainstream PCI Express (PCIe) segment by the end of the third quarter of this year, according to Taiwan graphics-card makers.
The new 128MB GeForce 6200 with TurboCache will support up to 256MB of system memory as well, the makers stated.