Small World

Posted on March 3, 2019 by Michal Necasek

The core of this story was originally a private e-mail, but I realized that it’s worth sharing with a slightly wider audience.

Readers may know that I’m very interested in the history of PC development tools, especially C compilers, and especially the Watcom C compilers. I therefore know that Watcom C/386 7.0 (1989) was the first Watcom 32-bit C compiler, and in fact one of the first 32-bit compilers for DOS. The first was probably MetaWare High C, which was never terribly popular due to the fact that it was both quite expensive and quite weird; it just never fit into the world of PCs all that well.

The Watcom C/386 7.0 compiler on the other hand was a close relative of Watcom’s award-winning 16-bit DOS compiler (versions 6.0, 6.5, and 7.0) which maintained a good degree of compatibility with Microsoft’s C compilers, and was therefore not nearly as alien as High C. Andrew Schulman took a look at the 386 compiler in a 1990 DDJ article.

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Posted in PC history, Watcom | 16 Comments

Reading From Void

Posted on February 21, 2019 by Michal Necasek

Recently I came across the following question: What happens when software reads the registers of a non-existent IDE controller? That is, what happens when software reads for example ports in the 1F0h-1F7h/3F6h range (primary IDE channel) when there is no device on that channel?

For the vast majority of devices, the answer is simple, reads return with all bits set (0FFh). That’s when no device decodes the given address, i.e. no one claims the bus cycle/transaction. But IDE is different, because there often is a device which decodes those addresses, namely the IDE controller, usually on the motherboard within the southbridge chip.

The answer then might be buried somewhere deep in the Intel ICH datasheets or similar documentation. But it’s not.

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Posted in BIOS, IDE, PC hardware | 10 Comments

Ancient NetWare OS/2 Requesters?

Posted on February 16, 2019 by Michal Necasek

Quite a while ago there was a discussion on this site about NetWare support for OS/2 versions prior to 1.3. Finding reliable information is difficult, especially when one doesn’t know exactly what to look for.

Spurred by the discovery of Novell NetWare 2.15 ELS II in my basement (obviously I knew it was some NetWare stuff, but until I learned much more about NetWare 2.x I didn’t realize it was a complete NetWare 286 server kit), I started pondering the question again. The NetWare release I had included a separately packaged NetWare Requester for OS/2 version 1.2 from May 1990.

NetWare Requester for OS/2 v1.2

It is very unclear from the documentation what the version of the Requester itself is, or if it even has one, but it’s crystal clear that it’s for OS/2 1.2 only, not any earlier version (and OS/2 1.3 had not been released yet). It relies on NWIFS.IFS, an Installable File System, which means it can’t possibly work with OS/2 1.0 or 1.1, as there was no IFS support in those versions.

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Posted in NetWare, OS/2, PC history | 13 Comments

Historical ATA Standard Drafts

Posted on February 12, 2019 by Michal Necasek

After some digging, I discovered that several old drafts of the original ATA standard (later known as ATA-1) have been out in the public all along, or at least for a very long time, cleverly hiding among hundreds of SCSI-related documents. I don’t seem to be the only one who missed them. Here they are:

These old revisions may provide the best surviving documentation of existing ATA/IDE practice as it existed in 1989 and onward. The first working document was introduced in March 1989. The ANSI X3.221 standard was officially approved on May 12, 1994. The actual document text was finalized in late 1993.

Note that the 1991 drafts still did not include any LBA support or removable media support. It did include the IDENTIFY DRIVE command as well as the (optional) READ/WRITE MULTIPLE and SET MULTIPLE MODE commands, as well as slave DMA transfers and PIO modes 0, 1, and 2 (up to 8.33 MB/s interface transfer rate).

July 2020 Update: Two “new” ATA draft versions have been discovered in BBS archives, namely revisions 3.0 and 4. While the R3.0 document was a plain ASCII file, the R4 file was not and used IBM code page 437 extended characters. The file presented above was converted to UTF-8; the original R4 document is here. As the notes in R3.2 indicate, R3.0 from late 1991 did not yet have any concept of LBA.

October 2021 Update: Two more and even older ATA drafts came to light. The very first and very incomplete draft (not yet called ATA) from March 1989, and a much more complete revision 2.1. The R2.1 draft is quite recognizable as ATA. The document was converted from WordStar to PDF, using the same 2-up printing style that X3T9.2 used for draft standards back in the day. The original R2.1 draft is here.

Posted in IDE, PC history, Storage | 15 Comments

NetWare 3.12 vs. Large IDE Disks

Posted on February 1, 2019 by Michal Necasek

Recently I had an occasion to find out why NetWare 3.12 using the shipped IDE driver (IDE.DSK) behaves, very, very strangely when let loose on disks bigger than about 500MB (a very foolish thing to even try). The driver loaded fine, discovered a 1GB disk fine, but when accessing it, it was extremely slow and produced a lot of errors.

After some debugging and disassembling IDE.DSK, the cause became obvious, but the chain of events that led to it was anything but.

The IDE.DSK driver in NetWare 3.12 dates from April 1993, meaning it’s older than the original ATA specification. The driver notably does not use LBA, because it was not yet standardized at the time; disks with LBA were perhaps just coming on the market, and they were generally not big enough to require LBA. Crucially, there were also no translating BIOSes yet.

The symptoms of the problem initially didn’t seem to make much sense. After working correctly for a short moment, NetWare would select non-existent device 1 (slave) on an IDE channel with only device 0 (master) present. Then it would read the alternate status register, get rather confused, and start endlessly re-calibrating and resetting the drive. In other words, completely unusable. So why would NetWare do such a thing?

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Posted in Bugs, IDE, NetWare, PC history | 51 Comments

Fox in the Crypt

Posted on January 19, 2019 by Michal Necasek

Some time ago I wrote a bit about examining the “branding” system which was used by XENIX and other SCO products and based on the crypt() UNIX library function. At the time I assumed that only SCO had used this scheme for their various UNIX derivatives and UNIX-based software. Imagine my surprise when I came across a copy of Multi-User FoxBASE+ 2.10 for DOS from June 1988 and found BRAND.EXE on the installation floppy. Could it really be the XENIX thing?

Sure enough, it really was. It even retained the same dual functionality in that if BRAND.EXE is renamed (or copied) to DEBRAND.EXE, it changes its behavior and can un-brand and encrypt a previously branded file.

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Posted in PC history, SCO, Software Hacks, Xenix | 3 Comments

Yep, Norton Did It

Posted on January 12, 2019 by Michal Necasek

Some time ago, the question of the oldest executable compression tool came up. EXEPACK was identified as a widespread and unexpectedly troublemaking specimen, but Realia SpaceMaker was reportedly older.

Only initially no one could come up with surviving executables compressed with SpaceMaker that were demonstrably older than EXEPACK (leave alone find old versions of SpaceMaker itself), although there were several unconfirmed hints that early versions of Norton Utilities used SpaceMaker.

Eventually an old executable compressed with SpaceMaker turned up: DVED.COM from September 1983, pre-dating the 1984 EXEPACK. But did Norton Utilities really use SpaceMaker?

Jeff Parsons of pcjs.org has now unearthed excellent circumstantial evidence: On floppies distributed with the Summer 1983 copies of the PC Disk Magazine, there were utilities authored by Peter Norton (though not specifically anything from the Norton Utilities). And those executables by Peter Norton were compressed with SpaceMaker.

In the meantime, the OS/2 Museum came into the possession of an image of an actual Norton Utilities 2.01 floppy. The files on the floppy are dated July 4, 1983, and yes, most of them are compressed with SpaceMaker. They contain the ‘MEMORY$’ signature near the beginning, and a decompression stub at the end. The rumors about Norton Utilities and SpaceMaker were true.

At this point, it is then known that yes, Peter Norton really used SpaceMaker for early Norton Utilities, and yes, SpaceMaker is really quite a bit older than EXEPACK; SpaceMaker may be considered the oldest known executable compression utility.

Posted in Compression, PC history | 10 Comments

My Second AMD

Posted on December 13, 2018 by Michal Necasek

A few weeks ago I became a happy owner of a ThinkPad A485, the first ThinkPad (together with the E485 and related variants) to use an AMD CPU. History buffs will know that it’s far from the first ThinkPad with a non-Intel CPU; the very first ThinkPad-branded laptops (ThinkPad 700/720 in 1992) used IBM’s own 486 SLC and SLC2 processors, the 1995 ThinkPad 365 used Cyrix Cx486DX4 processors, and the 1996 ThinkPad 365E sported the IBM-built Cyrix 5×86. But for over 20 years, ThinkPad meant Intel, until the Summer of 2018.

What I just realized is that the A485 is only the second AMD-based machine I ever bought. The first one was a Lenovo IdeaPad Z75 in 2014, a laptop with an AMD A10 APU based on the infamous Bulldozer microarchitecture. Ironically I never had any real complaints about the Z75’s CPU, but the low-res display was absolutely horrible and made the laptop too painful to use very often. Continue reading →

Posted in AMD, PC history, ThinkPad | 40 Comments

A Piece of History

Posted on November 21, 2018 by Michal Necasek

A few months ago I received a well-used but not abused copy of Rakesh K. Agarwal’s book 80×86 Architecture and Programming (Volume II): Architecture Reference, published by Prentice Hall in 1991. This is an unusually well-informed book, no doubt because Agarwal was a member of the team that implemented the 80386 at Intel, and wrote some of the 80386’s microcode himself. The book is notable for being the second and only volume of a series (Volume I was apparently never published). Agarwal is also a co-author of an informative article titled The Intel 80386—Architecture and Implementation, published in the IEEE Micro magazine in December 1985.

80×86 Architecture & Programming Vol II

My copy  80×86 Architecture and Programming (Volume II): Architecture Reference came with handwritten notes sprinkled over various bits of the C-like pseudo-code that the book uses to explain the workings of the 386 microcode, as well as several explanatory notes in the instruction reference section. Continue reading →

Posted in 386, Books, Cyrix, Intel, PC architecture, PC history | 6 Comments

DiskOnChip

Posted on November 6, 2018 by Michal Necasek

This is a guest post by Nils aka stecdose

What Is DOC?

I would like to present a „storage card“ for the XT bus (8-bit ISA bus) that I built from scrap parts. It is based on a small device called DiskOnChip, or DOC.

8-bit DOC Card

DOC-based storage card

I have been using the card for about 3 years now and it has proven to be quite a handy tool. The storage card shows up as drive C: in a system and it is even bootable! Continue reading →

Posted in Hardware Hacks, PC hardware | 12 Comments