. There have been questions on the price of Tandy's Mod 100 disk I/F. We squeezed hard, but the functionality just couldn't be had for less. . . It's really more than just a disk: . . 1) Z-80A CPU . 2) 1K ROM . 3) 4K System + 4K Video RAM . 4) Character Generator . 5) Monitor output - 80X25 and 40X25 . 6) RF Modulator - 40X25 - TV Ch 3/4 . 7) Floppy Disk Controller . 8) One 2D, 184K 5-1/4" FDD . (40 tracks of 18, 256-byte sect) . 9) Space for a second drive . 10) Disk BASIC Language . . It's ALMOST a complete computer! . . A special ZIF ("zero insertion force") connector permanently plugs into the bus socket. A new compartment door holds the connector in, and allows ribbon cable plug in. Transfer is FAST! All current I/O connectors are still useable. . . A 16K M100 is req'd. Disk BASIC occupies 4.5K RAM, but NOT a menu slot. Once loaded, only a 'cold start' can kill it. You need NOT dump memory to load. . . Video use is optional. Until 'SCREEN1' is executed, output is to LCD . . Command comparisons: . Memory Disk Comments ====== ====== =================== DIR LFILES SAVE"name" SAVE"0:name" LOAD"name" LOAD"0:name" . . (NOTE: .DO files SAVE/LOAD via . , as with cassette, plus 0: . or 1: drivespec. Most commands . specify memory vs. disk files by . use of drivespec) . PRINT# PRINT# Sequential write . DSKI$ See below INPUT# INPUT# Sequential input PSET (N/A) PRESET (N/A) . DSKO$ See below . LOC Gets current rec # . LOF Returns no. of last . record in file . BACKUP (Supports 1 & 2- . FORMAT (drive systems . . Filename extensions can be ANY 3 characters, not just ".DO" and ".BA". . . DSKO$ & DSKI$ format as follows: . . DSKO$[drive],[trk],[sect],[sw] . . The example writes the string to the specified sector and track, on the specified drive. When [sw]itch =0, the first half of the sector is accessed; when [sw]=1, the latter half is accessed. . . The minimum "access unit" is a "cluster" of 9 sectors. . Memory Map: . . FFFFH ---------- FFFFH ---------- . BASIC work BASIC work . area area . F5FOH ---------- ---------- . Strings, Disk BASIC . Stack area . ---------- E397H ---------- . Strings, . Stack Area . ---------- . User Area User Area . . . 8000H---------- 8000H ---------- . . I know of one other disk-only unit being developed. Price $699-799. It will use slower RS-232 via TELCOM (the commands may not be as convenient), and BACKUP and other capabilities are unknown. Sorry, confidentiality pro- hibits more info. Anyway, hope you'll look before judging price/performance ratio. . ...ej