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It was not that much of an engineering decision as a simple requirement for the chip to be feasible. At that time 40pin DIL was effectively the largest package

by dfox 4y ago

It was not that much of an engineering decision as a simple requirement for the chip to be feasible. At that time 40pin DIL was effectively the largest package that could be made at production scale.

kens 4y ago
Intel's decision to use a 40-pin chip was mainly because Intel had a weird drive for small integrated circuits. The Texas Instruments TMS9900 (1976) used a 64-pin package for instance, as did the Motorola 68000 (1979). For the longest time, Intel was fixated on 16-pin chips, which is why the Intel 4004 processor was crammed into a 16-pin package. The 8008 designers were lucky that they were allowed 18 pins. The Oral History of Federico Faggin [1] describes how 16-pin packages were a completely silly requirement, but the "God-given 16 pins" was like a religion at Intel. He hated this requirement because it was throwing away performance. When Intel was forced to 18 pins by the 1103 memory chip, it "was like the sky had dropped from heaven" and he had "never seen so many long faces at Intel." [1] pages 55-56 of http://archive.computerhistory.org/resources/text/Oral_History/Faggin_Federico/Faggin_Federico_1_2_3.oral_history.2004.102658025.pdf http://archive.computerhistory.org/resources/text/Oral_Histo...
- mardifoufs 4y ago
  I'm really curious about the arguments for sticking to those lower pin numbers. Was it for compatibility? Or packaging costs? Like what was the downside of using more pins (up until a certain point, obviously, but it seems like other manufacturers had no issues with going for higher pin numbers!)
  - kens 4y ago
    I think the argument for low pin counts was that Intel had a lot of investment in manufacturing and testing to support 16 pin packages, so it would cost money to upgrade to larger packages. But from what I read, it seems like one of those things that turned into a cultural, emotionally-invested issue rather than an accounting issue.
kjs3 4y ago
Doubtful. 42- and 48-pin dips same width as 40-pin were a thing around that time or not much later.

by dfox 4y ago

It was not that much of an engineering decision as a simple requirement for the chip to be feasible. At that time 40pin DIL was effectively the largest package that could be made at production scale.

kens 4y ago

Intel's decision to use a 40-pin chip was mainly because Intel had a weird drive for small integrated circuits. The Texas Instruments TMS9900 (1976) used a 64-pin package for instance, as did the Motorola 68000 (1979). For the longest time, Intel was fixated on 16-pin chips, which is why the Intel 4004 processor was crammed into a 16-pin package. The 8008 designers were lucky that they were allowed 18 pins. The Oral History of Federico Faggin [1] describes how 16-pin packages were a completely silly requirement, but the "God-given 16 pins" was like a religion at Intel. He hated this requirement because it was throwing away performance. When Intel was forced to 18 pins by the 1103 memory chip, it "was like the sky had dropped from heaven" and he had "never seen so many long faces at Intel." [1] pages 55-56 of http://archive.computerhistory.org/resources/text/Oral_History/Faggin_Federico/Faggin_Federico_1_2_3.oral_history.2004.102658025.pdf http://archive.computerhistory.org/resources/text/Oral_Histo...

mardifoufs 4y ago
I'm really curious about the arguments for sticking to those lower pin numbers. Was it for compatibility? Or packaging costs? Like what was the downside of using more pins (up until a certain point, obviously, but it seems like other manufacturers had no issues with going for higher pin numbers!)
- kens 4y ago
  I think the argument for low pin counts was that Intel had a lot of investment in manufacturing and testing to support 16 pin packages, so it would cost money to upgrade to larger packages. But from what I read, it seems like one of those things that turned into a cultural, emotionally-invested issue rather than an accounting issue.

kjs3 4y ago

Doubtful. 42- and 48-pin dips same width as 40-pin were a thing around that time or not much later.