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?
Intel Strikes Back
In the 1980s and 1990s, Intel fought x86 clones as hard as it could. NEC, AMD, Cyrix, UMC had been sued by Intel. AMD and Cyrix withstood Intel’s wrath, but others didn’t.
Intel went after C&T as well. Chips and Technologies used clean-room implementation techniques to avoid any kind of copyright infringement, but as is well known, that’s not a defense against patents.
In March 1992, Intel sued C&T for infringing five patents (InfoWorld, March 6, 1992, page 29). Texas Instruments became a party to the lawsuit in an effort to protect C&T; Texas Instruments had a broad patent cross-licensing agreement with Intel and manufactured the C&T Super386 chips.
At the same time C&T was going through a downturn, cutting costs and workforce. It was not in a position to fight Intel at the time.
The case was reportedly settled in 1993. At that point, the Super386 was most likely long out of production. Interestingly, C&T refocused its business on graphics chips and made a name for itself in the laptop video chip business. In 1997, Intel acquired C&T in order to get the portable graphics expertise.
More can be found for example here in the LA Times archive.
Too Little, Too Late
To put things in perspective, the C&T Super386 started volume shipments in early 1992, having been announced in September 1991. At that time, the 33 MHz 486 was readily available and the 66 MHz DX2 was right around the corner, with the Pentium on the horizon.
C&Ts standard 386s offered about 10% better performance at the same clock speed compared to Intel/AMD 386s, but that’s a very weak upgrade argument and unlikely to convince system designers to choose C&T.
While C&T also designed 386s with L1 cache, those weren’t pin-compatible. Those would have offered more substantial performance benefit, but couldn’t be plugged into any existing 386 system.
In contrast, Cyrix was much smarter in designing the 486DLC family to use the standard 386 socket and employing an array of clever hacks in order to enable L1 cache even on old 386 boards with no hardware or firmware support.
It’s not surprising that the C&T Super386 was only on the market for a few months. The announced SX variants never materialized and it’s unclear if the J38605DX processors with L1 cache were ever produced in any kind of volume or at all. It does not appear that any chips other than J38600DX survived into the third millennium.
Unfortunately the Super386 went out without a bang or a whimper, so it is difficult to tell quite how long it was on the market, what variants and clock speeds were produced, or how many units were sold.
What Is It?
Lest the reader think that the C&T Super386 is some kind of hoax—it was mentioned in the press in the early 1990s several times. The September 16, 1991 issue of InfoWorld (page 1) is one example, the paper of record is another.
The J38600DX looks to most software like a standard Intel/AMD 386. It should be possible to distinguish the Super386 by lack of certain errata common to all Intel/AMD CPUs. Some suggested using the lack of POPAD bug.
The Undocumented PC tool CPUTYPE incorrectly identifies the Super386 as a Cyrix part (there is no mention of the C&T 386 in Undocumented PC, even though every other 386 variant is covered). This suggests that the behavior with respect to undefined flags is different between C&T and Intel/AMD 386 cores.
Running CPUTEST, another Undocumented PC tool, revealed that the C&T Super386 implements at least one instruction not found in any other 386-class CPU. The first two bytes of the instruction are 0Fh, 18h. The C&T is almost certainly the only processor with no CPUID capability which supports that instruction, as the encoding was only used many years later.
How Does It Work?
After a brief test drive, it’s clear that the Super386 works well with typical DOS software, including EMM386, 32-bit protected-mode titles, and Windows 3.11. It performs slightly better than an equivalent Intel/AMD part, but the difference is not noticeable by the naked eye.
C&T no doubt benefited from its expertise with 386 chipset design and reverse engineering standard hardware (such as the VGA). C&T also produced an integrated 8086 clone, but a 386 is orders of magnitude more complex. Producing a working 386 clone was certainly not an easy task.
The Chips and Technologies Super386 was a valiant but short-lived effort to compete with Intel’s 32-bit CPUs. It was the first clean-room 386 clone on the market and also the first one to disappear. Were it not for the few mentions in the press and some surviving chips, it would be hard to believe that the C&T Super386 ever existed.
Wanted: Any kind of official C&T 386 documentation.