buffer support. The active display can be switched with ESC-X. A hardware reset button was added to the system. The keyboard, however, was not switched to the Selectric layout as had become standard, instead retaining the same ADM-3A-derived design as on Commodore's prior models. The VDC chip is largely useless for gaming since it has no sprites or raster interrupts. NTSC C128s will work with any CGA-type monitor (TTL RGB @ 15 kHz/60 Hz) such as the IBM 5153. However, PAL models of the C128 operate at 50 Hz and aren't compatible with most CGA monitors, which expect a 60 Hz refresh rate. Pin 7 of the VDC output (normally unused on CGA monitors) produces a monochrome NTSC/PAL signal, but no cable was provided for it and interested users had to make their own or purchase one on the aftermarket. Two new disk drives were introduced in conjunction with the C128: the short-lived single-sided 1570 and the double-sided 1571. A dual-disk 1572 model was announced but never produced. Later on, the 3.5-inch 1581 was introduced. All of these drives are more reliable than the 1541 and promise much better performance via a new "burst mode" feature. The 1581 drive also has more on-board RAM than its predecessors, making it possible to open a larger number of files at one time. BASIC 7.0 includes DLOAD and DSAVE commands to support loading and saving to disk without using the ,8 or other device number, and also a DIRECTORY command that reads a disk's catalog information directly to screen memory without overwriting BASIC memory as in BASIC 2.0. In addition, the C128 introduces auto-booting of disk software, a feature standard on most personal computers, but absent from Commodore machines up to that point. Users no longer have to type LOAD"*",8,1. BASIC also added a COLLECT command for removing "splat" files (files that were not closed properly and truncated to zero length). All 1571 drives will normally start up in native mode on the C128. If the user switches to C64 mode by typing "GO 64", the drive remains in native mode. But if C64 mode is activated by holding the Commodore key down when powering-up, the 1571 then goes into 1541 mode. This routine is necessary for software that performs low-level drive access. The C128 has twice the RAM of the C64, a far higher proportion of which is available for BASIC programming,