  We present Rossi X-ray Timing Explorer observations of the X-ray pulsar SMC
X-1. The source is highly variable on short time scales (< 1 h), exhibiting
apparent X-ray flares occupying a significant fraction (~3 %) of the total
observing time, with a recurrence time of ~100 s. The flares seem to occur over
all binary orbital phases, and correlate with the overall variability in the
light curve. We find a total of 323 discrete flares which have a mean full
width half maximum of ~18 s. The detailed properties of SMC X-1 do not vary
significantly between the flares and the normal state, suggesting that the
flare may be an extension of the normal state persistent emission with
increased accretion rates. The flares resemble Type II X-ray bursts from GRO
J1744--28. We discuss the origin of the SMC X-1 flares in terms of a viscous
instability near the inner edge of the accretion disk around a weakly
magnetized X-ray pulsar, and find this is consistent with the interpretation
that SMC X-1 is in fact an intermediate-stage source like GRO J1744--28.
