Original sentence: Though AGP cards did comprise a large proportion of graphics cards installed on PCs until quite recently, they are currently being phased out by both graphics card manufacturers and motherboard manufacturers (along with CPU manufacturers AMD and Intel)
Edited sentence: Though AGP cards did comprise a large proportion of graphics cards installed on PCs until quite recently, they are gradually being phased out by both graphics card manufacturers and motherboard manufacturers (along with CPU manufacturers AMD and Intel), only a small portion of product lineup from two major discrete graphics firm NVIDIA and ATI Technologies being released for AGP users who refuses to replace AGP products to PCI-E products (since the motherboard has to be replace altogether) to upgrade products supporting newer video standards