OS/2 Museum

Floppy Capacity Math

Posted on June 8, 2014 by Michal Necasek

After more or less accidentally coming across a BBS listing of various high-capacity floppy formatting programs, I began wondering: How much data can really be stored on a diskette in a PC floppy drive? And what’s the relationship between formatted and unformatted capacity? When I started doing the math, I realized that the problem is both simpler and more complex than I had thought. And that one megabyte is not like another.

Note: This discussion is limited to 3½” high-density floppies, by far the most common format, unless otherwise noted.

2.0 MB Unformatted Capacity

Since floppies store essentially analog signals, how is their theoretical capacity calculated? There are no addressable memory cells like those in RAM chips, so how does one arrive at 2 MB? The math is actually remarkably straightforward and has little to do with the medium and everything to do with the floppy controller (FDC) and drive. Continue reading →

Posted in Floppies, PC hardware | 41 Comments

The IBM PC BIOS and Intel ISIS-II

Posted on May 30, 2014 by Michal Necasek

An interesting question recently popped up: How exactly did IBM build the ROM BIOS for the IBM PC? Knowing what tools were used should make it possible to use the ROM listing published in the IBM PC Technical Reference and reproduce the ROM image.

Only one thing was clear—the PC BIOS wasn’t developed on a PC. With later IBM PC/AT and XT/286 ROMs, the situation is simple because the published listings identify IBM Macro Assembler 2.00 as the tool used. With the PC BIOS (and early AT BIOS), there’s no such identification.

The PC BIOS source code is remarkably straightforward. It is a single source file which does not use any macros. The one telltale marker is a $TITLE directive at the very beginning. No known version of MASM accepts this syntax… but at least one other assembler does. Continue reading →

Posted in BIOS, IBM, Intel, PC history | 54 Comments

PC Tech Journal

Posted on May 29, 2014 by Michal Necasek

One of the better PC magazines back in the day (that is, in the 1980s) was PC Tech Journal (or PCTJ for short), a sister periodical of PC Magazine published by Ziff-Davis. While PC Magazine was targeted at the general computer-buying public, the PC Tech Journal‘s audience were computer professionals—software developers and information systems managers.

PCTJ had a fairly high content to advertising ratio and the issues ran to around 200 pages rather than 300+ of the more ad-heavy magazines. Every issue contained several in-depth technical articles, as well as product reviews and product comparisons. Among the focus areas were development tools (assemblers, C/Fortran/Pascal/Basic etc. compilers), database managers, and networking software. Continue reading →

Posted in PC history, PC press | 7 Comments

IBM Power Series Exotica

Posted on May 23, 2014 by Michal Necasek

One might think that for example a ThinkPad Power Series 850 is an uncommon system, but such things are relative. The OS/2 Museum recently learned of not just one but two very rare Power Series systems, one of which is virtually a complete unknown. Both now live in the UK and both had been manufactured there (in Greenock, Scotland). The machines are a Power Series 800 and a Power Series 600.

In 1994, IBM started producing several PowerPC systems on a small scale and distributed them to software developers as part of the PowerPC development program. The most common was the Power Series 440 (6015) aka Sandalfoot, a desktop machine equipped with an early 66 MHz PowerPC 601. Operating system developers however also needed a portable in order to develop support for PCMCIA, LCD screens, and so on. That was the Power Series 800. What exactly the Power Series 600 was is less than obvious, but the system will be described in detail below.

Continue reading →

Posted in IBM, PowerPC | 7 Comments

Timing In Software Is Too Hard?

Posted on May 16, 2014 by Michal Necasek

I recently attempted to install RedHat Linux 3.0.3 (that’s the one from 1996, not RHEL 3.0) in VirtualBox. I thought I’d use the BusLogic SCSI emulation and the newer 1.3.57 Linux kernel. It did not work at all.

The problem was that the BusLogic SCSI driver, version 1.3.1 by the late Leonard N. Zubkoff, wouldn’t load. It failed with the following error message: ‘INQUIRE INSTALLED DEVICES ID 0 TO 7 FAILED – DETACHING’. That in turn caused the kernel to panic as it was unable to mount the root filesystem. The real problem turned out to be caused by a rather interesting collection of bugs in the Linux BusLogic driver. Continue reading →

Posted in Bugs, BusLogic, Linux, SCSI | 32 Comments

Microsoft OS/2 1.3… But Which One?

Posted on May 7, 2014 by Michal Necasek

A recent inventory at the OS/2 Museum revealed that two seemingly identical sets of Microsoft OS/2 1.30.1 disk images were in fact not identical at all. Probably thanks to the twilight status of OS/2 at Microsoft in the days of OS/2 1.3, Microsoft managed to confuse things to the point that it had to issue KB article Q99245 explaining the differences.

The trouble was that all the versions reported themselves as 1.3/1.30.1, and the SYSLEVEL.OS2 file which is supposed to differentiate between minor patch versions was exactly identical in all cases. However, timestamps and sizes of many system files (including the kernel, OS2KRNL) were not identical.

Continue reading →

Posted in LAN Manager, Microsoft, OS/2 | 26 Comments

Have You Seen This Board?

Posted on May 2, 2014 by Michal Necasek

The OS/2 Museum recently acquired this mystery 386 board (click on the image to see a high-resolution photo):

This is in theory a killer 386 board: onboard Am386DX-40, a socket for a replacement 386 or 486DLC processor, a FPU socket, 256KB cache, 8 SIMM slots for up to 32MB RAM, six 16-bit ISA slots, and best of all, a clock chip that can be set via jumpers to 16/20/25/33/40/50 MHz. Anyone familiar with typical 386 systems knows that such boards with user-selectable clock frequency are rather uncommon. Changing the clock speed normally involves replacing the crystal, which is hardly something one would want to do regularly. Continue reading →

Posted in 386 | 23 Comments

From the Annals of Branding

Posted on April 25, 2014 by Michal Necasek

The following picture shows four essentially identical Intel processors in the top row:

The real difference is that some of them are fabricated on an older process and thus sport a larger die size than others. (They’re also not all rated to operate at the same frequency, but that is not a design difference).

The more obvious difference is the labeling. From plain chips to i386 to i386 DX. The chips neatly illustrate an important chapter in Intel’s history. The leftmost chip was manufactured sometime in early 1988 and doesn’t look very different from the original 386s, or any other Intel chip of the era. It’s simply a slab of gray-brown ceramic with etched markings. The only noteworthy feature is the double-sigma (ΣΣ) marking indicating a 386 which reliably performs 32-bit operations. Continue reading →

Posted in 386, Intel | 14 Comments

OEM MS OS/2: 1987-1990

Posted on April 18, 2014 by Michal Necasek

When Microsoft started offering OS/2, the arrangement was roughly similar to how DOS 3.3 had been handled: Microsoft and IBM jointly developed the code, IBM maintained its own version, and Microsoft licensed an “adaptation kit” to OEMs. While the IBM and Microsoft versions were not identical, they were interchangeable from application perspective. There was no retail MS OS/2 package, and perhaps due to lower interest there also wasn’t a “packaged product” for OEMs (like there had been with MS-DOS since version 3.2).

Numerous OEMs licensed MS OS/2 1.0 in anticipation of it being the wave of the future, as Microsoft and IBM loudly proclaimed. OEM interest persisted through OS/2 1.1, but significantly waned by the time OS/2 1.2 was released. This coincided with Microsoft’s shift of focus towards Windows 3.0.

Pictured above are MS OS/2 1.0 (Epson OEM release) and MS OS/2 1.21 (Tandon OEM release). These were among the first and last OEM releases of OS/2. The Epson version was a relative latecomer, coming out in the second half of 1988. The Tandon version was released in summer 1990, when Windows 3.0 was already on the market. Continue reading →

Posted in Microsoft, OS/2 | 18 Comments

Multitasking MS-DOS 4.0, Goupil OEM

Posted on April 9, 2014 by Michal Necasek

The recently unearthed copy of the near-mythical Multitasking (aka European) MS-DOS 4.0 clearly did not want to be alone. James Lariviere, a kind reader of this blog, provided a disk image of multitasking DOS 4 which was released in 1986 by the French company SMT Goupil.

Microsoft’s contract with Goupil was the main reason why multitasking DOS 4 was completed at all. Goupil was the most important and perhaps even only OEM shipping multitasking DOS 4 (British ICL was the primary customer of the updated multitasking DOS 4.1 in 1987).

The machine that multitasking DOS 4 ran on was the Goupil G4, and a brief look at the machine’s specs reveals why Goupil was interested in multitasking DOS 4: The G4 was equipped with an 8 MHz Intel 80186 processor. Continue reading →

Posted in DOS, Microsoft, OS/2 | 29 Comments