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> Back in the 1980s, most of the major CPUs in the world were big-endian, while Intel bucked the trend being little-endian. The reason is that some engineer mad

> Back in the 1980s, most of the major CPUs in the world were big-endian, while Intel bucked the trend being little-endian. The reason is that some engineer made a simple optimization back when the 8008 processor... The article started talking about the VAX and how it was the gold standard everybody competed against. The VAX is little endian. Little endian is not a hack. It's a natural way to represent numbers. Its just that most languages in earth write words left to right while writing numbers right to left

segfaultbuserr 4y ago
VAX's predecessor, the PDP-11, is also a little-endian architecture in its basic form (and the PDP-11 was also a major source of influence to many microprocessor designers, just like VAX's influence on Unix workstations). The "PDP-endian" is only a quirk due to its Floating Point Unit's long integer and double-precision floating point formats. The FPU was an extra module attached to the processor, and the original PDP-11 did not even have an FPU. It only appeared on later models: on low-end machines a simplified FPU version was available for separate purchase with limited functionalities, and only high-end models had the full FPU. On a system without FPU installed, you basically don't need to worry about "PDP-endian", it's a pure little-endian machine. But for convenience, the Unix C compiler always stored long integers in PDP-endian to avoid swapping endians. Because the same Unix and C software ran on all machines with or without FPU, all Unix programmers needed to worry about it, thus the PDP-endian folklore. But why did the PDP-11 FPU use this strange format? @aka_pugs from Twitter did some digging, and found the PDP-endian was already in used as a softfloat format by DEC's PDP-11 Fortran compiler. So the FPU was made compatible with that...
- pencilguin 4y ago
  PDP-11 long ints were mixed- endian: high 16 bits, then low 16 bits. But within each half, the low 8 bits, then upper 8 bits. I was sometimes called the "NUXI" format, for how it scrambled the bytes in "UNIX".
  - segfaultbuserr 4y ago
    What I was saying is that the basic PDP-11 as original designed, is a pure 16-bit machine with no 32-bit capabilities. The Unix C and other compilers used the middle-endian format for 32-bit integers largely as an artificial choice to be compatible with its FPU, as middle-endian was FPU's native long integer format. But the FPU was only a later hardware extension, and was not an inherent part of the basic system, and it's not enforced by the basic PDP-11 insturction set. It's entirely possible to modify the UNIX C compiler to store long integers in little endian.
    - pencilguin 4y ago
      Yes.
ufo 4y ago
I think it's neat that Arabic, where we got the numbers from, is an RTL language. From their point of view the numbers are little endian.
- masklinn 4y ago
  OTOH Arabic got its numerals from indic systems, and indic scripts are generally LTR, which points to big median being “more natural”. It also matches the spelling of positional numerals in most languages, and does make sense from a convenience point of view: when talking it’s easier to round off by just stopping as you go than to figure out what rounding you should apply beforehand. If you spell out numbers in little-endian, once you start you’re committed to spelling it out in full, whereas big endian lets you stop at basically any point you feel like.
  - ithkuil 4y ago
    Zwei und dreissig ? Wahid wa ishrun? Yes most modern languages have lost little endiannes and those that kept it use only for the first 100 numbers. That's because for bigger and bigger numbers you're correctly pointing out that big endian is more useful when saying the numbers aloud since you can often ignore the less significant digits. My original point was different though: You can easily render little endian hexdumps equally readable as big endian hexdumps by just writing them in the order that is meant for numbers, namely right to left. We even align numbers to the right in spreadsheets. That's the same thing. Look at an old DEC manual (digital Unix, or VMS) and you'll see hexdumps where the numeric part is aligned from center towards the left and the ASCII part is aligned from the center to the right. With this layout you can easily read multibyte numbers naturally.
renox 4y ago
> Little endian is not a hack. It's a natural way to represent numbers To represent integers, for real numbers it's quite weird.
kens 4y ago
The history of why the 8008 was little-endian is interesting and predates the 8008. In 1970, the mostly forgotten company CTC released the Datapoint 2200, a desktop computer built from TTL chips (not a microprocessor) and sold as a programmable terminal. It had a serial processor using shift-register memory chips. It was an 8-bit processor but since it operated on one bit at a time, it had to start with the lowest bit to make addition work. As a result, it was little-endian. CTC talked to Intel and Texas Instruments to see if the processor could be put onto VLSI chips to replace the board of TTL chips. Texas Instruments produced the TMX 1795 processor, shortly followed by the Intel 8008, both processors cloning the Datapoint 2200's instruction set and architecture including little-endian. CTC rejected both processors and stuck with TTL. TI couldn't find another customer for the TMX 1795 and it vanished from history. Intel successfully marketed the 8008 as a general-purpose microprocessor. Its architecture was copied for the 8080 and then modified for the 16-bit 8086, leading to the x86 architecture that rules the desktop and server market. As a result, x86 has the little-endian architecture and other features of the Datapoint 2200. I consider the Datapoint 2200 to be one of the most influential processors ever, even though it's almost completely forgotten.
- kragen 4y ago
  Hmm, a minor quibble: "VLSI" would be normally more than 10k gates or 100k transistors on a single chip, wouldn't it? But the 8008 had only about 3500 transistors (I don't see an exact count in http://www.righto.com/2016/12/die-photos-and-analysis-of_24.html http://www.righto.com/2016/12/die-photos-and-analysis-of_24....) and so probably about 1000–1500 gates, so I think it should be called "LSI" rather than "VLSI". A funny thing about the 8008 is that Intel's manual for its instruction set is unnecessarily shitty — even if you didn't know the history with Datapoint, the Intel manual is obviously not by the people who designed the instruction set because it's in hexadecimal, a tradition sadly followed by the 8080 and 8086 manuals. The Datapoint manuals, by contrast, are all in octal, making the machine code enormously easier to understand. (The H8 I grew up with used an Intel chip, but the front panel monitor program used octal.)
  - kens 4y ago
    Yes, it's kind of amazing how the 8080/Z80/8086 instructions sets make much more sense in octal, but are always displayed in hexadecimal. In hex, you can kind of see some patterns, but everything is obvious in octal. The 6502 is also based on bit triples, but they grouped the bits from the top, so octal doesn't make things any better. The Datapoint 2200, by the way, used decimal decoder chips to decode the octal parts of the instruction set and simply ignored the 8 and 9 outputs.

segfaultbuserr 4y ago

VAX's predecessor, the PDP-11, is also a little-endian architecture in its basic form (and the PDP-11 was also a major source of influence to many microprocessor designers, just like VAX's influence on Unix workstations). The "PDP-endian" is only a quirk due to its Floating Point Unit's long integer and double-precision floating point formats. The FPU was an extra module attached to the processor, and the original PDP-11 did not even have an FPU. It only appeared on later models: on low-end machines a simplified FPU version was available for separate purchase with limited functionalities, and only high-end models had the full FPU. On a system without FPU installed, you basically don't need to worry about "PDP-endian", it's a pure little-endian machine. But for convenience, the Unix C compiler always stored long integers in PDP-endian to avoid swapping endians. Because the same Unix and C software ran on all machines with or without FPU, all Unix programmers needed to worry about it, thus the PDP-endian folklore. But why did the PDP-11 FPU use this strange format? @aka_pugs from Twitter did some digging, and found the PDP-endian was already in used as a softfloat format by DEC's PDP-11 Fortran compiler. So the FPU was made compatible with that...

pencilguin 4y ago
PDP-11 long ints were mixed- endian: high 16 bits, then low 16 bits. But within each half, the low 8 bits, then upper 8 bits. I was sometimes called the "NUXI" format, for how it scrambled the bytes in "UNIX".
- segfaultbuserr 4y ago
  What I was saying is that the basic PDP-11 as original designed, is a pure 16-bit machine with no 32-bit capabilities. The Unix C and other compilers used the middle-endian format for 32-bit integers largely as an artificial choice to be compatible with its FPU, as middle-endian was FPU's native long integer format. But the FPU was only a later hardware extension, and was not an inherent part of the basic system, and it's not enforced by the basic PDP-11 insturction set. It's entirely possible to modify the UNIX C compiler to store long integers in little endian.
  - pencilguin 4y ago
    Yes.

ufo 4y ago

I think it's neat that Arabic, where we got the numbers from, is an RTL language. From their point of view the numbers are little endian.

masklinn 4y ago
OTOH Arabic got its numerals from indic systems, and indic scripts are generally LTR, which points to big median being “more natural”. It also matches the spelling of positional numerals in most languages, and does make sense from a convenience point of view: when talking it’s easier to round off by just stopping as you go than to figure out what rounding you should apply beforehand. If you spell out numbers in little-endian, once you start you’re committed to spelling it out in full, whereas big endian lets you stop at basically any point you feel like.
- ithkuil 4y ago
  Zwei und dreissig ? Wahid wa ishrun? Yes most modern languages have lost little endiannes and those that kept it use only for the first 100 numbers. That's because for bigger and bigger numbers you're correctly pointing out that big endian is more useful when saying the numbers aloud since you can often ignore the less significant digits. My original point was different though: You can easily render little endian hexdumps equally readable as big endian hexdumps by just writing them in the order that is meant for numbers, namely right to left. We even align numbers to the right in spreadsheets. That's the same thing. Look at an old DEC manual (digital Unix, or VMS) and you'll see hexdumps where the numeric part is aligned from center towards the left and the ASCII part is aligned from the center to the right. With this layout you can easily read multibyte numbers naturally.

renox 4y ago

> Little endian is not a hack. It's a natural way to represent numbers To represent integers, for real numbers it's quite weird.

kens 4y ago

The history of why the 8008 was little-endian is interesting and predates the 8008. In 1970, the mostly forgotten company CTC released the Datapoint 2200, a desktop computer built from TTL chips (not a microprocessor) and sold as a programmable terminal. It had a serial processor using shift-register memory chips. It was an 8-bit processor but since it operated on one bit at a time, it had to start with the lowest bit to make addition work. As a result, it was little-endian. CTC talked to Intel and Texas Instruments to see if the processor could be put onto VLSI chips to replace the board of TTL chips. Texas Instruments produced the TMX 1795 processor, shortly followed by the Intel 8008, both processors cloning the Datapoint 2200's instruction set and architecture including little-endian. CTC rejected both processors and stuck with TTL. TI couldn't find another customer for the TMX 1795 and it vanished from history. Intel successfully marketed the 8008 as a general-purpose microprocessor. Its architecture was copied for the 8080 and then modified for the 16-bit 8086, leading to the x86 architecture that rules the desktop and server market. As a result, x86 has the little-endian architecture and other features of the Datapoint 2200. I consider the Datapoint 2200 to be one of the most influential processors ever, even though it's almost completely forgotten.

kragen 4y ago
Hmm, a minor quibble: "VLSI" would be normally more than 10k gates or 100k transistors on a single chip, wouldn't it? But the 8008 had only about 3500 transistors (I don't see an exact count in http://www.righto.com/2016/12/die-photos-and-analysis-of_24.html http://www.righto.com/2016/12/die-photos-and-analysis-of_24....) and so probably about 1000–1500 gates, so I think it should be called "LSI" rather than "VLSI". A funny thing about the 8008 is that Intel's manual for its instruction set is unnecessarily shitty — even if you didn't know the history with Datapoint, the Intel manual is obviously not by the people who designed the instruction set because it's in hexadecimal, a tradition sadly followed by the 8080 and 8086 manuals. The Datapoint manuals, by contrast, are all in octal, making the machine code enormously easier to understand. (The H8 I grew up with used an Intel chip, but the front panel monitor program used octal.)
- kens 4y ago
  Yes, it's kind of amazing how the 8080/Z80/8086 instructions sets make much more sense in octal, but are always displayed in hexadecimal. In hex, you can kind of see some patterns, but everything is obvious in octal. The 6502 is also based on bit triples, but they grouped the bits from the top, so octal doesn't make things any better. The Datapoint 2200, by the way, used decimal decoder chips to decode the octal parts of the instruction set and simply ignored the 8 and 9 outputs.