Commodore 1571
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Image:Commodore 1571.png The Commodore 1571 was Commodore's high-end 5¼" floppy disk drive. With its double-sided drive mechanism, it had the ability to utilized double-sided, double-density (DS/DD) floppy disks natively. This was in contrast to its predecesors, the 1541 and 1570, which could read or write such disks only by manually flipping them over to access the second side.
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 C128D had a 1571 compatible drive integrated in the system unit. A double-sided disk on the 1571 could hold 332 KB of data, formatted as 1,328 disk blocks of 256 bytes each.
The 1571 featured a "burst mode" when used in conjunction with the C128 (although not when used with the Commodore 64 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 had originally 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 [1].
For compatibility with copy-protected software, the 1571 could also closely emulate the 1541. This mode was the default when the drive was used in conjunction with a C64.
The 1571 was noticeably quieter than its predecessor and tended to run cooler as well, even though, like the 1541, it had the power supply inside the unit (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 CBM DOS V3.0 1571, an improvement over the 1541's V2.6.
Unlike the 1541, which was limited to GCR formatting, the 1571 could do both GCR and MFM disk formats. A C128 in CP/M mode equipped with a 1571 was capable of reading and writing floppy disks formatted for many CP/M computers; specifically, the following formats:
With additional software, it was possible to read and write to DOS-formatted floppies as well. Numerous commercial and public-domain programs for this purpose became available, the best known being SOGWAP's "Big Blue Reader". Although the C128 could not run any DOS-based software, this capability allowed data files to be exchanged with PC users.
Like the 1541, Commodore initially had difficulty keeping up with 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, one from Oceanic and one from Blue Chip, appeared, but legal action from Commodore quickly succeeded in driving them from the market.
Commodore announced a dual-drive version of the 1571, to be called the 1572, but quickly cancelled it, reportedly due to technical difficulties with the 1572 DOS.
References
- Ellinger, Rainer (1986). 1571 Internals. Grand Rapids, MI: Abacus Software (translated from the original German edition, Düsseldorf: Data Becker GmbH). ISBN 0-916439-44-5.