by rasz | 2026-03-03 15:19:18+00:00
> two years to reverse engineer the 386 and implement their own clean-room design

Am386 was _not_ clean room. It was a copy, just not 1:1 mask copy because of https://en.wikipedia.org/wiki/Semiconductor_Chip_Protection_... AMD admitted to copying 386 microcode and parts for 486

Sept. 4, 1993 LA Times https://www.latimes.com/archives/la-xpm-1993-09-04-fi-31680-...

>AMD said Friday that its “independently derived” 486 microprocessor borrowed some microcode from Intel’s earlier 386 chip.

In 1995 settlement AMD fully admitted copying and agreed to pay $58mil penalty while Intel gave them official license for 386, 486 microcode and infamous patent 338(mmu). Intel really wanted a legal win confirming validity of their patent 338 to threaten other competitors like UMC https://www.cpushack.com/2012/09/06/intel-vs-the-world-the-3...

> Effectively, Intel forced AMD into remaining a CPU generation behind for more than a decade

Nobody forced AMD to copy 1:1 Intel designs. AMD was lazy in late 80s. Am2900 was ancient seventies design, Am29000 was BAD and expensive. 1991 Q1 25MHz CPU prices according to "Semiconductor procurement worldwide" 1991-1993 by Dataquest:

Am29K $135 ~15-20 mips only with expensive SRAM/caches
88100 $82 ~15 mips but supposedly TERRIBLE CPU according to Apple engineers
R3000 $150 25 mips?
SPARC $100 20 mips

Cant name a single successful or popular product using one except for K5 CPU being build around 29K core.

Companies like Cyrix somehow managed to build novel x86 implementations, but still had to employ legal tricks due to that stupid AMD settlement providing precedent for legality of patent 338. Cyrix was forced to manufacture with IBM and TI as both had iron clad foundry agreements with Intel. Cyrix Corp. v. Intel Corp https://law.justia.com/cases/federal/district-courts/FSupp/8...

"Section 1.23 of the IBM Agreement states that IBM Licensed Products "shall mean IHS Products ..." The only logical conclusion is that the parties meant those IHS Products specifically identified in Section 1.2 of the Agreement. Section 1.2 does not limit the products to IBM designed products."

"Therefore, IBM has the right to act as a foundry and to make, use, lease, sell and otherwise transfer the microprocessors in question to Cyrix free of any claims of patent infringement."

>while AMD sold entry-level CPUs at the low end of the market.

thats on AMD not being able to design good product. Their breaks came in form of first acquiring NexGen and selling their chip as K6 and later hiring bunch of great DEC engineers who helped design K7 architecture.

>More modern fabs meant lower production cost, which meant better profit margins.

In one of Computer History Museum interviews Intel engineer mentioned releasing 386SX to battle AMD at the low end and that it cost Intel $5 to manufacture one including packaging in 1988. There was plenty of margin to go around even at the low end if you were good at what you were going. Intel initially priced 386SX at $219, money printer goes BRRRR. i386SX-25 went from Q1 1990 $184 to Q4 1992 $59 due to losing AMD Am386 microcode lawsuit. This move relegated Am386DX-40 Q2 1991 $231 flagship to the title of Q1 1993 $51 bottom feeder.

>Running at the same clock rate, AMD’s version of the 386 had essentially identical performance to the Intel original.

because 1:1 clone

>Value-oriented power users

no, bargain bin shoppers. I should know, I was one of them :)

>40 MHz 386 was faster than a 20 MHz Intel 486SX, and roughly comparable to a 25 MHz 486SX.

Am386DX-40 was somewhere between 486SX16 and 20 when running 32bit code like DOOM. Cyrix Cx486DLC-40 was about 486SX-25.

> favored the AMD Am386DX-40 well into the 486 era

Am386DX came out well into 486 era :) no one favored Am386DX. You bought it or Cyrix Cx486DLC if you couldnt afford 486 platform.

I loved my little Am386DX. 8MB, 40MB stepper motor IDE drive, random VGA, Aztech Sound Blaster 2 clone with matching Mitsumi x2 CDROM. All scrounged together from used discounted parts piece by piece in $50 increments.