the open market. The first Portables used MS-DOS essentially identical to PC DOS 1.10 except for having a standalone BASIC that did not require the IBM PC's ROM Cassette BASIC, but this was superseded in a few months by MS-DOS 2.00 which added hard disk support and other advanced features. The initial Portables are similar to the 16K-64K models of the IBM PC in that the BIOS was limited to 544K of RAM and did not support expansion ROMs, thus making them unable to use EGA/VGA cards, hard disks, or similar hardware. After DOS 2.x and the IBM XT came out, Compaq upgraded the BIOS. Although the Portable was not offered with a factory hard disk, users commonly installed them. Starting in 1984, Compaq began offering a hard-disk equipped version in the Portable Plus. The original hard disks offered would be 10 or 21 megabytes, although bad sectors often reduced the space available for use. Reception BYTE wrote, after testing a prototype, that the Compaq Portable "looks like a sure winner" because of its portability, cost, and high degree of compatibility with the IBM PC. Its reviewer tested IBM PC DOS, CP/M-86, WordStar, SuperCalc, and several other software packages, and found that all worked except one game. PC Magazine also rated the Compaq Portable very highly for compatibility, reporting that all tested applications ran. It praised the "rugged" hardware design and sharp display, and concluded that it was "certainly worth consideration by anyone seeking to run IBM PC software without an IBM PC". Later Models The Compaq Portable Plus simply had a hard drive to replace one floppy disk drive, and logos and badges with gold backgrounds instead of silver. Independent computer stores were previously doing this upon request of users, and Compaq saw this as a lost revenue opportunity. In 1985, Compaq introduced the Portable 286, although it was replaced by the more compact Portable II in a redesigned case within a few months. The Portable 286 featured a full height hard disk, and the options of one half-height floppy drive, two half-height floppy drives, or a half-height floppy drive and a tape backup drive The Compaq Portable 286, Compaq's version of the PC AT was offered in the original Compaq Portable chassis; equipped with 286 and a high-speed hard drive The Compaq Portable II – was smaller and lighter version of Compaq Portable 286; it was less expensive