|
The TRS-80 Model II was a computer system launched by Tandy in October 1979, and targeted at the small-business market. Despite its name, the Model II was not an upgrade of the original (Model I) TRS-80, but an entirely different system. The Model II was succeeded by the compatible TRS-80 Model 12, Model 16 and Model 16B and the Tandy 6000. ==Model II== As a professional business machine, the Model II used state-of-the-art hardware and had numerous features not found in the primitive Model I such as DMA, vectored interrupts, a detachable keyboard, and port instead of memory-mapped I/O. It sported 80x25 text and a singled-sided 500k 8" floppy drive, and either 32 or 64k of RAM, along with two RS-232 ports and a Centronics-standard parallel port. The video memory could be banked out, so that the whole 64k address space could be used for main memory. Unlike most computers, it had no BIOS ROM except a small boot loader (the BIOS was loaded off the boot floppy). Because of this and the use of port I/O, almost all of the Model II's memory could be used by software. The Model II ran the TRSDOS operating system (renamed to TRSDOS-II starting with version 4.0) and BASIC. TRSDOS for the Model II was not compatible with TRSDOS for the Model I; thus the Model II never had the same breadth of available software as the Model I (a situation aggravated by the fact that Tandy discouraged third-party software development). This was somewhat mitigated by the availability of the CP/M operating system for the Model II from third parties such as Pickles & Trout. Three internal expansion slots could be used for add-on cards such as additional serial ports and a video board that allowed bitmap graphics. The Model II architecture theoretically supported up to 512K RAM via a bank switchable upper 32K page segment (up to 15 32K pages were supported). However, the machine did not provide enough card slots to physically upgrade the RAM to 512K. This was because RAM was provided via 32K or 64K cards and only a few open card slots were available on a standard Model II since the basic configuration of the machine took up 4 slots. Tandy offered a desk custom-designed for the Model II for US$370. It could hold an additional three 8" disk drives or up to four 8.4Mb hard drives (the Model II allowed three external floppy drives to be daisy-chained to it). In 1981, the 64K Model II computer was $3350 and the "primary unit" 8.4Mb hard disk another $4040 by mail-order from Radio Shack's dealer in Perry, Michigan; MSRP in the company's own stores was higher.〔Kilobaud (Microcomputing ) (magazine), November 1981, page 57, "TRS-80 Discount", Perry Oil & Gas Incorporated 137 North Main St. Perry MI 48872 (advertisement).〕 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「TRS-80 Model II」の詳細全文を読む スポンサード リンク
|