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486DLC/SLC were not really "crippled versions", they were completely different CPU designs that used the 486 name as Intel wasn't able to stop other companies f

by ido 4y ago

486DLC/SLC were not really "crippled versions", they were completely different CPU designs that used the 486 name as Intel wasn't able to stop other companies from using a number (one of the reasons for naming the next cpu family "pentium" which they could trademark/copyright). The crippled versions were the 486SXs, which disabled the FPU.

dspillett 4y ago
> The crippled versions were the 486SXs, which disabled the FPU. Though for many use cases at the time, that wasn't a massive issue. Many games didn't take advantage of the FPU until far into the 486 era, they were only starting to when the Pentium and its competitors came out (a killer for Cyrix's P5-era chips which despite a very strong integer performance had terrible floating-point umph). There were 487 FPU co-processors, to upgrade 486SXs, though unlike the 287 and 387 before them they weren't really co-processors, they were actually full 486 chips and the main CPU was disabled when they were present. The name caused confusion because SX in 386 meant something completely different (there was no built-in FPU to disable): a 16-bit data bus instead of 32-bit and 24-bit address bus, along with more minor changes, so it would work on cheaper motherboards originally designed with 286's in mind.
- bluedino 4y ago
  The 486SLC kept the 16-bit bus, but I don't remember what it was about the DLC but it was much slower than an Intel 486 of the same clockspeed even thought it was a full 32-bit chip. I want to say it was something like it still used 386 motherboard designs (in both cases).
  - myself248 4y ago
    ISTR the SLC introduced SMM that allowed laptops to use the main CPU to do things that otherwise would've required an elaborate embedded controller. And thus began the trend of having entire layers of functionality in the CPU that were outside the view of the OS which thought it was running at ring 0....
- Koshkin 4y ago
  > There were 487 FPU co-processors Curiously, those were actually the full 486DX CPUs that, when installed, would simply disable the old CPU and take over its function as well.

by ido 4y ago

dspillett 4y ago

> The crippled versions were the 486SXs, which disabled the FPU. Though for many use cases at the time, that wasn't a massive issue. Many games didn't take advantage of the FPU until far into the 486 era, they were only starting to when the Pentium and its competitors came out (a killer for Cyrix's P5-era chips which despite a very strong integer performance had terrible floating-point umph). There were 487 FPU co-processors, to upgrade 486SXs, though unlike the 287 and 387 before them they weren't really co-processors, they were actually full 486 chips and the main CPU was disabled when they were present. The name caused confusion because SX in 386 meant something completely different (there was no built-in FPU to disable): a 16-bit data bus instead of 32-bit and 24-bit address bus, along with more minor changes, so it would work on cheaper motherboards originally designed with 286's in mind.

bluedino 4y ago
The 486SLC kept the 16-bit bus, but I don't remember what it was about the DLC but it was much slower than an Intel 486 of the same clockspeed even thought it was a full 32-bit chip. I want to say it was something like it still used 386 motherboard designs (in both cases).
- myself248 4y ago
  ISTR the SLC introduced SMM that allowed laptops to use the main CPU to do things that otherwise would've required an elaborate embedded controller. And thus began the trend of having entire layers of functionality in the CPU that were outside the view of the OS which thought it was running at ring 0....
Koshkin 4y ago
> There were 487 FPU co-processors Curiously, those were actually the full 486DX CPUs that, when installed, would simply disable the old CPU and take over its function as well.