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The Commodore 128, also known as the C128, C-128, C= 128,〔The "C=" representing the graphical part of the logo〕 or occasionally CBM 128, is the last 8-bit home computer that was commercially released by Commodore Business Machines (CBM). Introduced in January 1985 at the CES in Las Vegas, it appeared three years after its predecessor, the bestselling Commodore 64. The C128 is a significantly expanded successor to the C64, with nearly full compatibility. The newer machine has 128 kB of RAM in two 64 kB banks, and an 80-column color video output. It has a redesigned case and keyboard. Also included is a Zilog Z80 CPU which allows the C128 to run CP/M, as an alternative to the usual Commodore BASIC environment. The presence of the Z80 and the huge CP/M software library it brings, coupled with the C64's software library, gives the C128 one of the broadest ranges of available software among its competitors. The primary hardware designer of the C128 was Bil Herd, who had worked on the Plus/4. Other hardware engineers were Dave Haynie and Frank Palaia, while the IC design work was done by Dave DiOrio. The main Commodore system software was developed by Fred Bowen and Terry Ryan, while the CP/M subsystem was developed by Von Ertwine. ==Technical overview== The C128's keyboard includes four cursor keys, an Alt key, Help key, Esc key, Tab key and a numeric keypad. None of these were present on the C64. Previous Commodores had only two cursor keys, which required using the shift key to move the cursor up or left. This arrangement was retained on the 128, for C64 compatibility. The lack of a numeric keypad, Alt key, and Esc key on the C-64 were an issue with some CP/M productivity software when used with the 64's Z-80 cartridge. A keypad was requested by many C64 owners who spent long hours entering machine language programs using MLX.〔(【引用サイトリンク】title=The Official Book for the Commodore 128 )〕 Many of the added keys match ones present on the IBM PC's keyboard and made the new computer more attractive to business software developers.〔(【引用サイトリンク】title=The Official Book for the Commodore 128 )〕 While the 128's 40 column mode closely duplicates that of the C64, an extra 1K of color RAM was made available to the programmer, as it was multiplexed through memory address 1. The 128's power supply was improved over the 64's unreliable design, being much larger and equipped with cooling vents and a replaceable fuse. Instead of the single 6510 microprocessor of the C64, the C128 incorporated a two-CPU design. The primary CPU, the 8502, is a slightly improved version of the 6510 capable of being clocked at 2 MHz. The second CPU is a Zilog Z80 which is used to run CP/M software, as well as to initiate operating mode selection at boot time. The two processors cannot run concurrently, thus the C128 is not a multiprocessing system. The C128's complex architecture includes four differently accessed kinds of RAM (128 kB main RAM, 16-64 kB VDC video RAM, 2 kNibbles VIC-II Color RAM, 2-kB floppy-drive RAM on C128Ds, 0, 128 or 512 kB REU RAM), two or three CPUs (main: 8502, Z80 for CP/M; the 128D also incorporates a 6502 in the disk drive), and two different video chips (VIC-IIe and VDC) for its various operational modes.〔(http://oldcomputers.net/c128d.html )〕〔(http://www.datasalen.se/Utstallning/Data/CBM/commodore128deng.htm )〕 Early versions of the C128 occasionally experience temperature-related reliability issues due to the use of an electromagnetic shield over the main circuit board. The shield was equipped with fingers that contacted the tops of the major chips, ostensibly causing the shield to act as a large heat sink. A combination of poor contact between the shield and the chips, the inherently limited heat conductivity of plastic chip packages, as well as the relatively poor thermal conductivity of the shield itself, resulted in overheating and failure in some cases. The SID sound chip is particularly vulnerable in this respect. The most common remedy is to remove the shield, which Commodore had added late in development in order to comply with FCC radio frequency regulations. The C128 has three operating modes. ''C128 Mode'' (native mode) ran at 1 or 2 MHz with the 8502 CPU and had both 40- and 80-column text modes available. ''CP/M Mode'' uses both the Z80 and the 8502〔Commodore CP/M Source code and programmers' manual.〕 and is able to function in both 40- or 80-column text mode. ''C64 Mode'' is nearly 100 percent compatible with the earlier computer. Selection of these modes is implemented via the Z80 chip. The Z80 controls the bus on initial boot-up and checked to see if there is a CP/M disk in the drive, if there are any C64/C128 cartridges present, and if the Commodore key (C64-mode selector) is active on boot-up. Based on what it finds, it will switch to the appropriate mode of operation. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Commodore 128」の詳細全文を読む スポンサード リンク
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