Microsoft Windows NT 3.51
Microsoft launched Windows NT 3.1 (for "New Technology") in July 1993. This first version inaugurated a family of operating systems that would reshape the professional computing landscape. The platform targeted Intel x86 and RISC processors. IDC analysts then defined an advanced operating system by its 32-bit APIs, preemptive multitasking managing processes and threads, integrated networking, and demand-paged virtual memory.
Feedback on Windows NT 3.1 pushed Microsoft to develop version 3.51, which was released in 1995. Two variants appeared: Windows NT Workstation and Windows NT Server. The former sought maximum responsiveness for interactive applications, while the latter optimized network performance. This choice reflected a clear segmentation strategy between workstations and servers.
Windows NT Workstation 3.51 reduced its memory footprint by 4 to 8 MB compared to its predecessor. 16-bit applications gained 25 to 50% performance on typical desktop configurations. On RISC systems (Alpha AXP and MIPS), Intel emulation for Windows 16-bit and MS-DOS applications received substantial improvements.
Windows 16-bit applications could now run in separate DOS virtual machines (VDMs). A crashing application no longer compromised the stability of other programs. Integration mechanisms like DDE (Dynamic Data Exchange) and OLE (Object Linking and Embedding) continued to function across VDMs.
Microsoft enriched Windows NT 3.51 with OpenGL, this 3D graphics function library initially developed by Silicon Graphics. A committee bringing together Digital Equipment Corporation, IBM, Intel, and Microsoft validated this technology. CAD, industrial design, and scientific analysis applications leveraged these new 3D capabilities.
Network connectivity improved significantly. The system integrated a compatible NetWare redirector that facilitated access to files and printers on Novell servers via IPX/SPX. The TCP/IP stack doubled its performance. PPP and SLIP enabled TCP/IP connections over asynchronous lines, attracting the UNIX and Internet communities.
Security was reinforced with account lockout after several failed login attempts. This protection blocked brute force attacks on passwords. NTFS gained per-file and per-directory compression, reducing data size by 40 to 50% depending on their nature.
Microsoft improved reliability. When a fatal system error occurred, Windows NT 3.51 automatically saved the memory state to a debug file and restarted. This approach, borrowed from UNIX systems, maximized the availability of network-connected machines.
The system targeted four categories of users. First, enterprises sought its stability to limit the costs of frequent restarts. With 2,000 workstations restarting 4 times per month for 5 minutes, an organization lost 8,000 hours of productivity per year. Developers appreciated its robustness for creating Win16 and Win32 applications. Technical users (engineers, scientists, statisticians) exploited its performance for their intensive calculations, often ported from UNIX. Computing enthusiasts adopted its innovations without losing productivity.
Peripheral management extended to PCMCIA cards for high-end laptops. The system now handled SCSI scanners and HP plotters. Absolute input mode facilitated the use of digitizers and touch screens. Windows NT 3.51 also integrated drivers for Cinepak and Indeo video formats.
The user interface adopted Windows 95’s common controls. File Manager, Print Manager, and other system applications inherited a modernized presentation with tooltips. The login sequence was customizable, allowing for example bank smart cards.
Microsoft offered different technical support formulas, including telephone assistance available 24 hours a day for critical incidents. Enterprises could choose different service levels, from basic support to Premium contracts with guaranteed response time. A network of authorized centers completed the system.
Administration was simplified with five backup modes: normal (complete copy), copy (without marking), incremental (modified files), differential (changes since the last complete backup), and daily (same-day modifications). The system documented each backup with the tape name, date, operator identity, and sequence number.
Windows NT 3.51 marked an important milestone in Microsoft systems history. Its solid architecture, performance, and advanced features attracted enterprises and demanding users. The system established technical foundations that would influence future versions of Windows, demonstrating Microsoft’s ability to finally design reliable professional systems.