The Amstrad/Schneider PC-1640 was the successor of the successful PC-1512. The PC-1640 came standard with 640kByte of RAM and a 20 or 30 MByte Hard Drive. The graphics capabilities on the PC-1640 were upgraded to EGA standard, the PC-1512 had enhanced CGA compatibility.

Just as the PC-1512, the power supply was housed in the monitor with a 14-pin plug going from the monitor to the base unit. Many peripheral interface boards were hard-wired on the main board, including serial and parallel interfaces and the disk controller. An area of RAM was set aside, called NVR (non-volatile RAM), which was battery-backed (AA batteries!!) and stored configuration data of the machine. This also stored the real-time clock.

The PC-1640 had an ISA slot that could be used for a 3rd party graphics card. The internal graphics could, unlike the PC-1512, be disabled, but in practice not many users chose to do this, since the machine still needed the old monitor for the power supply of the computer. So if the new graphics card modes were not supported by the original monitor, your choice was to sit with two monitors on your desk, or not upgrade at all.

Just as the PC-1512 the PC-1640 came bundled with DR-DOS. MS-DOS was not included on this computer because the price-point was too high for Amstrad. Digital Research took this as a chance to promote their version of DOS and offered DR-DOS at a very aggressive price point to Amstrad.

MS-DOS (Microsoft Disk Operating System) originated in 1981 when Microsoft acquired QDOS (Quick and Dirty Operating System) from Seattle Computer Products and adapted it for IBM’s upcoming 8088-based personal computer. Initially branded as IBM PC-DOS 1.0 for IBM, and MS-DOS for other vendors, it provided a single-user, single-tasking environment that was heavily inspired by CP/M. The system was structured around a kernel (IBMBIO.COM and IBMDOS.COM in PC-DOS, IO.SYS and MSDOS.SYS in MS-DOS) that interfaced with hardware and implemented system services, plus a command interpreter (COMMAND.COM) that offered a user interface and executed batch files. Early versions supported only 160 KB or 320 KB floppy disks, a flat directory structure, and a very limited system call API.

Technically, MS-DOS was designed around the Intel 8086/8088’s segmented memory model, giving programs access to up to 640 KB of conventional memory, with the upper memory area reserved for system BIOS and hardware. The OS itself was not re-entrant and offered no process isolation: a single foreground program owned the machine at any given time, and the kernel simply provided file and device I/O calls. Devices were abstracted as special files (CON, PRN, AUX, NUL), allowing consistent access via the same system calls used for disk files. Its filesystem, FAT12, offered a simple, space-efficient design suitable for floppy media but imposed limits such as 8.3 filenames and small maximum volume sizes.

As the IBM PC platform expanded, MS-DOS evolved rapidly. Version 2.0 (1983), designed for the IBM XT with a hard drive, introduced FAT16, hierarchical subdirectories, file handles, and device drivers that could be dynamically loaded. Later releases added support for larger disks, expanded memory (via EMS/XMS standards), internationalization, and more sophisticated batch scripting. Version 3.x aligned with the IBM AT and its 80286 CPU, supporting 1.2 MB floppies, larger hard disks, and network redirectors. By version 4.0, MS-DOS began showing signs of strain under the growing complexity of PC hardware, and memory management became a recurring challenge due to the 640 KB conventional memory limit and the awkward use of extended and expanded memory schemes.

Despite being inherently single-tasking, MS-DOS was extended through third-party multitasking shells and Microsoft’s own attempts such as MS-DOS 4.0 Multitasking (rarely used). Eventually, MS-DOS served as the underlying runtime for Windows 3.x, which leveraged DOS for file and device I/O but implemented a cooperative multitasking GUI environment on top. With the release of Windows 95 and later, MS-DOS was gradually absorbed into Windows as a bootstrapping layer and compatibility subsystem. Nonetheless, MS-DOS’s simple architecture, reliance on BIOS and device drivers, and its widespread adoption made it the de facto standard for microcomputer operating systems throughout the 1980s, shaping software design and hardware standards for years to come.

The 8086 CPU from Intel is a 16-bit microprocessor and was designed between 1976 and 1978. The 8086 is the foundation of the x86 cpu architecture which is Intel's most successful line of processors.

The 8086 used the same microarchitecture as the 8-bit 8008, the 8080, and the 8085. This allowed assembly language programs to run seamlesly on the 8086. New instructions and features were added and the bus structure was designed to allow for collaboration with co-processors, such as the 8087 that was released later.