Nvidia (NVDA) shares are trading higher ahead of the company’s announcement Tuesday of results for its fiscal second quarter ended July. On July 2, Nvidia pre-announced a big top-line shortfall, forecasting revenue of $875 million to $950 million; at the time the consensus had been for revenue of over $1 billion. The new Street view: $908.4 million in revenue and profits of 12 cents a share.

The Street sees Q3 revenue of $1.01 billion with EPS of 22 cents. For the January 2009 fiscal year, the consensus is for $4.2 billion and $1.01 a share. For FY 2010, the consensus is $4.43 billion and $1.22.

Several analysts weighed in Monday with previews of tomorrow’s report. The key issues: loss of market share to AMD and a rough pricing environment.

Cowen’s Daniel Berenbaum, who maintains an Outperform rating on the shares, concedes that he underestimated the loss of market share to the ATI unit of Advanced Micro Devices (AMD), and says that “it’s tough to argue that there’s a rush to put new money to work here.” But he nonetheless thinks that “cost reductions and new GPU product cycles over the course of the next 12 months will bolster the core business and allow new product introductions in high-end computing and mobility to flourish.”

Patrick Wang, an analyst with Wedbush Morgan, repeated his Buy rating on the stock Monday, but cut his price target to $16 from $18. He’s expecting “weak” Q2 results, due to share loss and ASP pressure on desktop graphics processors. And he says Q3 guidance could disappoint. Wang today cut his FY 2009 EPS estimate to 87 cents from 89 cents; for 2010, he sees $1.07, down from $1.20.

Nicholas Aberle, analyst with Caris & Co., Monday repeated his Average rating on NVDA, cautioning that July quarter reesults could come in at the low end of guidance. “The current perfect storm for NVDA come as AMD has launched the first solid product family [in graphics chips] in over three years and NVDA has dropped the ball on unit cost,” he writes. “With uncertainty likely to persist past Tuesday’s report, we believe it will be difficult for investors to quantify a worst case scenario for gross margin and overall risk/reward.”

Interesting that despite all the caution, NVDA shares are on the rise: NVDA closed Monday up 23 cents, or 2.1%, to $11.23.