Difference between Quadro NVS 55/280 PCI & NVS 280 SD

In order to download and install the correct NVIDIA driver for my
MEPIS Linux system, I'd like to know how to find out which <of these two
NVIDIA-offered drivers> is the one I should download and install:

- Quadro NVS 55/280 PCI
- Quadro NVS 280 SD

IBM only tells me that my video card is:
"NVIDIA Quadro4 280NVS (LFH-60), AGP 8X, with 64MB double-data-rate (DDR)
synchronous dynamic random access memory (SDRAM) video memory and dual
analog connectors (or dual digital monitor capability with the purchase of
an additional pigtail cable)".

[Incidentally, I only have a single, 15 pin VGA monitor connected via the
pigtail cable running to the 60 pin LFH connector on the computer.]


Which of the above two is the one I should download?


Thanks

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