several planar memory in parallel. The PC-9801VX introduced a blitter chip called the EGC (Enhanced Graphic Charger). It had raster operations and bit shifting. In 1993, NEC introduced a 2D Windows accelerator card for PC-98, called the Window Accelerator Board, which employed a S3 86C928. Video cards for C-bus, local bus and PCI are also available from other manufacturers. DirectX 7.0a is the last official supported version for PC-98. Sound The first generation of PC-9801s (the E, F and M models) only have an internal buzzer. PC-9801U2 and later models can change the sound frequency by controlling the programmable interval timer, like the PC speaker. The PC-8801mkIISR home computer, introduced in 1985, has a Yamaha YM2203 FM synthesis, an Atari joystick port and BASIC sound commands. The optional PC-9801-26 sound card is based around these features, although in some PC-9801 models it is integrated with the motherboard. It was replaced by the PC-9801-26K to support the 80286 CPU. This became the most common sound card for playing in-game music on the PC-98. The PC-9801-26K was succeeded by the PC-9801-73 (1991) and PC-9801-86 (1993) sound card, which employs the YM2608 FM synthesis and adds support for CD-quality PCM playback. The latter has a reasonable price and fully backward compatibility with the 26K sound card, so it gained strong support in PC games. Due to lack of DMA support and poor sound drivers, it often has issues in Windows and created popping and clicking sounds. Late PC-9821 models use the Crystal Semiconductor's Windows Sound System audio codec to resolve this, but the newer sound chip is not compatible with the older conventional sound cards. The PC-9801-118 (1995) sound card has both the YMF297 (hybrid of YM2608 and YMF262) and the WSS audio, but its PCM playback is not compatible with the 86 sound card. Roland released a music production starter kit for PC-98, which combines the MT-32 synthesizer module, a MIDI interface card and a MIDI editing software. Creative Labs developed a C-bus variant of Sound Blaster 16. Keyboard The first PC-9801 model has the same keyboard layout as the PC-8801's except it adds conversion key XFER and 5 function keys. Later models have some minor changes: NFER, 15 function keys, LED status indicators, and replacing CAPS and alternate action switches. Mouse The bus mouse and interface card kit was introduced for PC-98 in 1983. The PC-9801F3 and later models have a