3 ms·

Bit like comparing a 8086 to the latest and greatest, still have support for the instructions of the time, but been lots of additions since. At least comparing

by Zenst 6y ago

Bit like comparing a 8086 to the latest and greatest, still have support for the instructions of the time, but been lots of additions since. At least comparing the ISA level.

fiddlerwoaroof 6y ago
Didn’t PowerPC have some unique extensions that distinguishes it from the the POWER CPUs?
- wmf 6y ago
  Yeah, but Power3 and onward actually implement the PowerPC ISA so the differences are smaller than they appear.
johnklos 6y ago
No. Not even remotely close. The 8086 was an 8 bit processor with some 16 bit extensions and segment registers. This is worlds different than 32 bit x86. They're worlds apart. The PowerPC 601 is functionally quite similar to modern 32 bit PowerPC.
- foobiekr 6y ago
  The 8086 was a 16 bit CPU. Every register is 16 bit as is the internal and external data bus (the address space is actually 20 bits, but that's a different issue).
  - johnklos 6y ago
    ...except it barely more of a 16 bit processor than a Z80, and had 8 bit instructions, extendable to longer, like the Z80. Aside from the 20 bit addressing and 16 bit offset, the 8088 and Z80 were equivalent. Or should we call the Z80 a 16 bit processor?
    - jlokier 6y ago
      > Or should we call the Z80 a 16 bit processor? Z80 is classified as an 8-bit processor because it has an 8-bit internal data bus to the register file.⁽¹⁾ This is visible in instruction timings: 16-bit INC BC takes longer than 8-bit INC B because the 16-bit register access takes two internal data cycles compared with one internal cycle for 8-bit. Intel 8086 is classified as a 16-bit processor because it has a 16-bit internal data bus to the register file. This is visible in instruction timings: 16-bit register operations generally take the same time as 8-bit register operations.⁽²⁾ ⁽¹⁾ Trivia: Z80 also has a 16-bit internal address bus and 4-bit ALU. ⁽²⁾ Actually 8-bit INC AL takes longer than 16-bit INC AX, opposite way around from Z80. But that's because of a longer instruction encoding, not architecture. MOV AL,BL takes the same time as MOV AX,BX.)

by Zenst 6y ago

Bit like comparing a 8086 to the latest and greatest, still have support for the instructions of the time, but been lots of additions since. At least comparing the ISA level.

fiddlerwoaroof 6y ago

Didn’t PowerPC have some unique extensions that distinguishes it from the the POWER CPUs?

wmf 6y ago
Yeah, but Power3 and onward actually implement the PowerPC ISA so the differences are smaller than they appear.

johnklos 6y ago

No. Not even remotely close. The 8086 was an 8 bit processor with some 16 bit extensions and segment registers. This is worlds different than 32 bit x86. They're worlds apart. The PowerPC 601 is functionally quite similar to modern 32 bit PowerPC.

foobiekr 6y ago
The 8086 was a 16 bit CPU. Every register is 16 bit as is the internal and external data bus (the address space is actually 20 bits, but that's a different issue).
- johnklos 6y ago
  ...except it barely more of a 16 bit processor than a Z80, and had 8 bit instructions, extendable to longer, like the Z80. Aside from the 20 bit addressing and 16 bit offset, the 8088 and Z80 were equivalent. Or should we call the Z80 a 16 bit processor?
  - jlokier 6y ago
    > Or should we call the Z80 a 16 bit processor? Z80 is classified as an 8-bit processor because it has an 8-bit internal data bus to the register file.⁽¹⁾ This is visible in instruction timings: 16-bit INC BC takes longer than 8-bit INC B because the 16-bit register access takes two internal data cycles compared with one internal cycle for 8-bit. Intel 8086 is classified as a 16-bit processor because it has a 16-bit internal data bus to the register file. This is visible in instruction timings: 16-bit register operations generally take the same time as 8-bit register operations.⁽²⁾ ⁽¹⁾ Trivia: Z80 also has a 16-bit internal address bus and 4-bit ALU. ⁽²⁾ Actually 8-bit INC AL takes longer than 16-bit INC AX, opposite way around from Z80. But that's because of a longer instruction encoding, not architecture. MOV AL,BL takes the same time as MOV AX,BX.)