SSE MW-1000 Mini-Winchester

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    mw1000Unidentified photo of the MW-1000 from another website

    The MW-1000 or “Mini-Winchester” was the last PET/CBM product from Small Systems Engineering Ltd. It combined all of the features of the SoftBox and the HardBox along with 1 or 2 full height 5.25″ hard drives into one box.

    In SoftBox mode, the MW-1000 is a standalone CP/M computer with a 4 MHz Z80, 64K RAM, and hard disk that can use either the PET/CBM or RS-232 for its terminal. In HardBox mode, the MW-1000 provides a hard disk for the PET/CBM that is compatible with all the usual CBM DOS commands. Having all of these capabilities makes the MW-1000 one of the most advanced PET/CBM peripherals made.


    No actual MW-1000 hardware has been found. However, former SSE engineer Terence Smith had the MW-1000 system disks and gave them to me. Jeremy Gugenheim, another SSE engineer, helped identify the MW-1000’s hard disk controller. With these pieces, I worked together with Martin Hoffmann-Vetter to reverse engineer the disks. This information is based on our work.

    The MW-1000 is one box that houses a SoftBox board, a hard disk controller board, and up to two full-height 5.25″ ST-506 style hard drives. From the heads/cylinders configurations in the menus, we believe Rodime RO200-series drives were used.

    The SoftBox board in the MW-1000 is configured the same as the normal SoftBox. It has only one memory map and it is the same as the SoftBox (60K RAM + 4K ROM). The ROM contains a CP/M BIOS and is based on the SoftBox BIOS. The 8K ROM code from the HardBox was relocated to run from RAM and stored on the hard disk. We do not have the MW-1000 ROM, but we think it probably loads this code from disk on power-up.

    The MW-1000 does not have a Corvus-style external port like the SoftBox and HardBox. Instead, the I/O port is connected to an internal “David Junior” type controller from Konan Corporation. The MW-1000 chassis can hold up to two full height 5.25″ drives.


    From the user’s perspective, we think the MW-1000 functions almost identically to the SoftBox and HardBox. We know that the MW-1000 stores HardBox code on its hard disk and loads it into RAM, so we think it must be able to switch between SoftBox and HardBox modes automatically somehow. The exact mechanism for how it does this is not yet known.

    The main difference in usage is in the HardBox configuration programs. These programs have been ported from the PET/CBM to SoftBox CP/M. A new program, MWDOS291.COM, is used to write the HardBox firmware to the protected area of the first hard disk.

    Since the CP/M and Commodore filesystems are not compatible, the MW-1000 allows the user to divide the first hard disk into halves. It can be used for all SoftBox (CP/M), all HardBox (CBM DOS), or half each. The second hard disk is only available for CP/M.


    Since no MW-1000 hardware has been found, it is necessary to create a replica of it. The diskettes have provided all of the system software and enough clues about the hardware to build it. The parts required are a standard SoftBox board, a David Junior hard disk controller, a hard drive with ST-506 interface, and a power supply.

    The BIOS of the MW-1000 has not been found. We know from reverse engineering the disks that the BIOS is based on the SoftBox BIOS with changes for the new hard disk controller and additions to load the HardBox code from the hard disk into RAM. It should be possible to modify the SoftBox BIOS to arrive at a functional equivalent of the real MW-1000 ROM. There should be no differences from the user’s perspective.


    Mention – Excerpt from “The Whole PET Catalog” book
    Advertisement – Commodore Computing International, Feb 1983