OS/2 Museum

Intel 486 Errata?

Posted on December 6, 2015 by Michal Necasek

There don’t seem to be any specification updates or errata lists for any Intel 486 CPU anywhere. It’s odd because there are specification updates for 386s (and of course Pentiums) from Intel, and because the embedded 486s continued to be produced for a long long time (standard 486s well into the 2000s).

The 486 was released back when Intel believed that publishing errata would be damaging and it seems the policy was never changed, as it had been for the Pentium (after the infamous FDIV fiasco).

Someone, somewhere has the errata sheets. Anyone want to share? Continue reading →

Posted in 486, Intel, PC history | 22 Comments

MS C 4.0 Documentation Added

Posted on November 27, 2015 by Michal Necasek

Another library expansion. This time it’s Microsoft C 4.0 documentation (1986)—because it’s not available online, is not easy to find offline, and because Jeff asked for it.

MS C 4.0 was an early Microsoft compiler, implementing first glimpses of the not-yet finalized ANSI C standard. It was released in summer 1986 and superseded first by the little-known Microsoft C 5.0 in 1987, and more importantly by the very popular Microsoft C 5.1 in early 1988.

Microsoft C 4.0 was notable for supporting Microsoft Windows. It was likely the compiler used for developing most Windows 1.x software available on the market.

An important addition in version 4.0 was CodeView, a full-screen source level debugger which superseded DEBUG and SYMDEB. 30 years ago, source level debuggers were fancy!

Posted in C, Documentation, DOS, Microsoft | 7 Comments

More on the C&T Super386

Posted on November 20, 2015 by Michal Necasek

Since last week’s post, more information about the Chips and Technologies C&T has come to light.

It now appears that at least some 38605DX processors were made. Whether there is any surviving working system is still an open question (since a special motherboard would be required as well). On the other hand, there is still is no evidence that any of the SX variants existed beyond samples.

There is more on the sort-of-SMM in the Super386, called SuperState V. The U.S. Patent 5,455,909 provides an overview of the feature. The caveat is that the patent’s existence does not necessarily imply a specific implementation. The F8680 PC/CHIP is better documented but its SuperState R (R for Real, V for Virtual?) is not necessarily the same as the Super386’s SuperState V.

Last but not least, thanks to a reader suggestion and a kind stranger, an unfinished manuscript of the Super386 Programmer’s Reference Manual has been located. While it is very incomplete, it sheds some light on the one mysterious undocumented Super386 instruction. Continue reading →

Posted in 386, C&T, Documentation | 32 Comments

The Forgotten 386

Posted on November 13, 2015 by Michal Necasek

The CPUs that fit into a 386 socket are well known: Intel’s original, AMD’s exact copy, and Cyrix/TI upgrades. There is also IBM’s 386SLC which is close to a 386 but can’t be plugged into a standard 386 socket. The photo below shows a selection of eight more or less common PGA-132 processors with Intel/AMD and Cyrix/TI cores:

The ninth is not like the others—a C&T Super386.

The Chips & Technologies Super386 or J38600DX is so obscure that it’s not mentioned in most lists of x86 processors and not detected by most software. Yet the C&T 386 was the first commercially available clean-room clone of the 386, beating Cyrix to market by several months (AMD’s Am386 chips were exact copies and not clones). So what went wrong? Continue reading →

Posted in 386, C&T, PC history | 25 Comments

More ISA VGA Benchmarks

Posted on November 6, 2015 by Michal Necasek

After establishing that Trident VGA cards are indeed very slow, the natural follow-up question is: Are there cards even slower than that? But not some 8-bit VGA card from the 1980s (or a Realtek from the 1990s), and not some exotic CAD accelerator, but rather some mainstream 16-bit ISA graphics card.

Those who remember the latter days of ISA graphics cards may guess the “winner”: Early S3 graphics accelerators! Such as this one:

This specimen from mid-1992 was not a cheap card, but it was popular. It was a graphics accelerator with 1MB VRAM (not DRAM) and an 80 MHz DAC. The S3 86C911 chip kicked off a very successful line of graphics adapters. Continue reading →

Posted in Cirrus Logic, IBM, S3, VGA | 9 Comments

About Those Trident VGAs…

Posted on October 30, 2015 by Michal Necasek

An earlier post mentioned that the performance of Trident-based ISA VGA cards leaves much to be desired. A reader pointed out that such cards tend to have switchable 8-bit/16-bit bus width and performance might suffer if the card is incorrectly jumpered.

After examining two different Trident cards in detail, it is clear that yes, those jumpers exist… but the Trident-based cards are so bad that it doesn’t matter anyway.

Trident TVGA8900B

The first card was this:

It’s a 1991 ISA VGA card sold under the Octek brand, using a Trident TVGA8900B chip. It’s notable for sporting full 1MB video memory, not typical for a cheap 1991 card. Continue reading →

Posted in Trident, VGA | 17 Comments

Fast Unaccelerated VGA?

Posted on October 26, 2015 by Michal Necasek

For the purpose of comparing the relative real-world performance of various processors, it’s useful to run CPU and graphics-intensive benchmarks such as 3DBench or DOOM. To avoid benchmarking the graphics card instead, the VGA has to have enough headroom so that it doesn’t become the bottleneck. And because benchmarking 386 (i.e. ISA-only) systems is desired, it has to be a (16-bit) ISA VGA card.

On the other hand, accelerated graphics performance is uninteresting here; only standard VGA matters. So what’s a fast ISA VGA card? That’s a question which is not as easy to answer as it perhaps should be. Continue reading →

Posted in 386, ATi, S3, VGA | 27 Comments

The Nearly Ultimate 386 Board

Posted on October 5, 2015 by Michal Necasek

Spurred by the acquisition of a 386 ZIF socket adapter, I revived the semi-mysterious 386 board acquired over a year ago. To recap, the board is unusual in that it has CPU frequency configurable via jumpers, but I had trouble getting anything other than the soldered-on Am386DX-40 to run.

Experimenting with the PGA processor socket showed somewhat odd behavior: Plugging in another Am386DX-40, the board worked and both CPUs seemed to run. Lowering the frequency, it was even possible to have an Intel 386 CPU running in the PGA socket. But a Cyrix or TI processor would not work. The current theory is that as delivered, a CPU plugged into the PGA socket would be active, but the soldered-on processor ran as well. As long as the two were more or less identical, the system would work. Continue reading →

Posted in 386, Hardware Hacks, PC hardware | 9 Comments

This Is How to Feed It

Posted on September 25, 2015 by Michal Necasek

The question of how to feed an Intel SBT2 board has been answered thanks to a very kind blog reader. Interestingly, there are two different answers. The official one is this:

The Delta Electronics RPS-350 B power supply comes from a SC5000 chassis and is exactly what the SBT2 board calls for. It has the right 24-pin ATX-style power connector and the right 10-pin special I²C power connector, as well as the uncommon auxiliary connector. It’s a redundant power supply, meaning that the system should survive the failure of one of the two PSUs within the housing (notice the two handles on the back).

With the SSI switch panel (likewise from a SC5000), my SBT2 started up right away (well, almost, see below). Integrated graphics, 4GB RAM (this is a board from 2000!), 1GHz Xeon. Continue reading →

Posted in Intel, PC hardware | 14 Comments

The Vanishing Dream

Posted on September 11, 2015 by Michal Necasek

By sheer coincidence, three different yet similar wavetable daughterboards landed on my desk. They’re of different ages but all use Dream synthesizer chips. Together they provide an interesting window into the evolution of MIDI synthesizers.

The oldest daughterboard is from mid-1994 and was likely sold under the TerraTec WaveSystem brand. It uses the SAM9203 synthesizer chip. The middle-aged board is from late 1994 and uses the widespread SAM9233 synth chip. It was sold as Hizon DB333 and under other names. The newest of the bunch is significantly more modern—a Dreamblaster S1 from 2014 using a SAM2195 all-in-one chip. Continue reading →

Posted in MIDI, Sound | 2 Comments