By all indications, Advanced Micro Devices (NASDAQ: AMD) is having a tougher time coping with crashing demand for PCs than rival Intel (NASDAQ: INTC). When AMD earned a buy rating from Bernstein last February, that rating was partly based on the idea that AMD would hold up better in a tough PC market. Rasgon knocked down his rating on AMD to market perform on Tuesday, citing a deteriorating PC market and the fact that AMD is being hit harder by the downturn than Intel.