Timing Two LMXBs: The Revived Transient X1658-298 and the 21-hr Dipper X1624-490

After a 21-year quiescence, the transient LMXB X1658-298 resumed its strong, persistent X-ray emission in April 1999. We present results from a series of 22+ eclipse timing observations performed with RXTE and USA from revival through Jan 2000, including an analysis of eclipse transitions and a new ephemeris. No Hz or kHz QPOs are detected in the persistent emission, or the rises to the 9 bursts observed. We also present visually-striking early results from a 4-day observation of X1624-490. The PCA data show five complex dips in unprecedented detail. For the first time, dipping is detected up to 15 keV. Unusual flaring is observed outside dips, limited to E > 8 keV. When analyzed with complex continuum models, these data will provide a wealth of information on the spectral behavior of X1624-490. We have also combined PCA and ASM data to derive the first accurate ephemeris for this source.