Advanced Micro Devices Inc forecast lower quarterly revenue as a shortage of hard drives and a shaky economy hurts PC makers, sending its shares lower after-hours.

Like larger rival Intel Corp , AMD has been wrestling with slow demand for chips as consumers increasingly buy Apple Inc's iPad instead of laptops.

Also hurting sales of processors, PC manufacturers have been struggling to obtain enough hard drives to meet production targets after flooding last year ruined factories and sensitive machinery in Thailand, the world's No. 2 exporter of the components.

Intel beat scaled-back quarterly earnings expectations last week after warning that the hard drive shortage was hurting PC production. It also warned of lower revenue in the current quarter.

AMD depends more on sales of PC processors for its revenue than does Intel, which sells proportionally more chips for servers. The fact that it expects a similar drop in revenue as Intel suggests AMD might have taken some market share.

AMD's guidance being equivalent to Intel's suggests to us that AMD has picked up roughly 100 to 110 (basis) points of market share in the PC space. said JoAnne Feeney, an analyst at Longbow Research. That guidance could also mean AMD is picking up more server market share.

AMD said revenue in the fourth quarter rose 2 percent from the year-ago period, to $1.69 billion.

But it said revenue in the quarter ending in March would fall 8 percent from the previous quarter, plus or minus 3 percentage points, equivalent to $1.504 billion to $1.606 billion.

Analysts on average expected fourth-quarter revenue of $1.716 billion and March-quarter revenue of $1.595 billion, according to Thomson Reuters I/B/E/S.

Non-GAAP earnings in the quarter were $138 million, compared with $106 million in the year-ago period. Non-GAAP earnings per share were 19 cents, compared with 14 cents in the year-ago quarter.

Shares of AMD were down 2.6 percent at $6.36 in extended trade after closing up 0.15 percent at $6.53.

(Reporting by Noel Randewich in San Francisco; Editing by Steve Orlofsky and Matthew Lewis)