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The Commodore 1571 is Commodore's high-end 5¼" floppy disk drive. With its double-sided drive mechanism, it has the ability to use double-sided, double-density (DS/DD) floppy disks natively. This is in contrast to its predecessors, the 1541 and 1570, which can fully read and write such disks only if the user manually flipped them over to access the second side. Because flipping the disk also reverses the direction of rotation, the two methods are not interchangeable; disks which had their back side created in a 1541 by flipping them over would have to be flipped in the 1571 too, and the back side of disks written in a 1571 using the native support for two-sided operation could not be read in a 1541. == Release & features == The 1571 was released to match the Commodore 128, both design-wise and feature-wise. It was announced in the summer of 1985, at the same time as the C128, and became available in quantity later that year. The later C128''D'' had a 1571-compatible drive integrated in the system unit. A double-sided disk on the 1571 would have a capacity of 340 kB (70 tracks, 1,360 disk blocks of 256 bytes each); as 8 kB are reserved for system use (directory and block availability information) and, under of each block serve as pointers to the next logical block, = 337,312 B or about were available for user data. (However, with a program organizing disk storage on its own, all space could be used, e.g. for data disks.) The 1571 features a "burst mode" when used in conjunction with the C128 (although not when used with the Commodore 64 (without modifying hardware) or VIC-20). This mode replaced the slow bit-banging serial routines of the 1541 with a true serial shift register implemented in hardware, thus dramatically increasing the drive speed. Although this originally had been planned when Commodore first switched from the parallel IEEE-488 interface to a custom serial interface, hardware bugs in the VIC-20's 6522 VIA shift register prevented it from working properly.〔(【引用サイトリンク】url=http://www.binarydinosaurs.co.uk/Museum/Commodore/c64/c64notes.php )〕 For compatibility with copy-protected software, the 1571 could closely emulate the 1541. This mode was the default when the drive was used in conjunction with a C64; while always being able to read and write the 1541's of single-sided, in this mode it also would format disks single-sided and transfer data at 1541 speed. An undocumented command allowed the drive to format and use the second side of a disk, but only in single-sided mode. The 1571 was noticeably quieter than its predecessor and tended to run cooler as well, even though, like the 1541, it had an internal power supply (later Commodore drives, like the 1541-II and the 3½" 1581, came with external power supplies). The 1541-II/1581 power supply makes mention of a 1571-II, hinting that Commodore may have intended to release a version of the 1571 with an external power supply. However, no 1571-IIs are known to exist. The embedded OS in the 1571 was an improvement over the Early 1571s had a bug in the ROM-based disk operating system that caused relative files to corrupt if they occupied both sides of the disk. A version 2 ROM was released, but though it cured the initial bug, it introduced some minor quirks of its own - particularly with the 1541 emulation. Curiously, it was also identified as V3.0. As with the 1541, Commodore initially could not meet demand for the 1571, and that lack of availability and the drive's relatively high price (about US$300) presented an opportunity for cloners. Two 1571 clones appeared, one from Oceanic and one from Blue Chip, but legal action from Commodore quickly drove them from the market. Commodore announced a dual-drive version of the 1571, to be called the 1572, but quickly canceled it, reportedly due to technical difficulties with the 1572 DOS. It would have had four times as much RAM as the 1571, and twice as much ROM. The 1572 would have allowed for fast disk backups of non-copy-protected media, much like the old 4040, 8050, and 8250 dual drives. The 1571 built into the European plastic-case C128 D computer is electronically identical to the stand-alone version, but 1571 version integrated into the later metal-case C128 D (often called C128 DCR, for D Cost-Reduced) differs a lot from the stand-alone 1571. It includes a newer DOS, version 3.1, replaces the MOS Technology CIA interface chip, of which only a few features were used by the 1571 DOS, with a very much simplified chip called 5710, and has some compatibility issues with the stand-alone drive. Because this internal 1571 does not have an unused 8-bit input/output port on any chip, unlike most other Commodore drives, it is not possible to install a parallel cable in this drive, such as that used by SpeedDOS, Dolphin DOS and some other fast third-party Commodore DOS replacements. 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 1571」の詳細全文を読む スポンサード リンク
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