games are available for the Tandy TRS-80. Because of bandwidth problems in the interface card that replaced the TV's tuner, the display loses horizontal sync if large areas of white are displayed. A simple half-hour hardware fix corrects the problem. The graphics are displayed at a resolution of 64×16 character positions on a screen measuring wide and tall. Each character is composed of a 2×3 matrix of pixels, and corresponds to one byte of the 1 KB video memory used by the TRS-80. In each of those bytes, the first six bits control which pixel is displayed. The seventh bit is ignored, and the eighth toggles graphics mode. The reason that the seventh bit is ignored is due to the company's decision to have only seven 2102 static-RAM chips installed on the computer's motherboard instead of eight to keep the manufacturing cost low. Thus, there are no lowercase letters in the TRS-80 character set of an unmodified Model I, and the number of both graphics symbols and alphanumeric symbols is 64. This can be worked around by deleting the unused bit and piggybacking an eighth 2102 chip onto another. The alphanumeric symbols are displayed in 5×7 matrices of pixels. The 1978 manual for the popular word processor Electric Pencil came with instructions for modifying the computer. Although the modification needs to be disabled for Level II BASIC, its design became the industry standard and was widely sold in kit form, along with an eighth 2102 chip. Later models came with the hardware for the lowercase character set to be displayed with descenders. With higher-density RAM chips and purpose-built monitors, higher-resolution crisp displays are obtainable; 80×24-character displays are available in the Model II, Model 4, and later systems. The Model I has no built-in speaker. Square-wave tones can be produced by outputting data to the cassette port and plugging an amplifier into the cassette "Mic" line. Most games use this ability for sound effects. An adapter was available to use Atari joysticks. Peripherals Cassette tape drive User data was originally stored on cassette tape. Radio Shack's model CTR-41 cassette recorder was included with the US$599 package. The software-based cassette tape interface is slow and erratic; Green described it as "crummy ... drives users up the wall", and the first issue of 80 Micro has three articles on how to improve cassette performance. It is sensitive to audio volume, and the computer