2 ms·
> Also, the arbitrary "Oh, and the registers are 80 bits wide" is also just one of those weird "Where did that number come from?". One of the features that was
by matja 19d ago
> Also, the arbitrary "Oh, and the registers are 80 bits wide" is also just one of those weird "Where did that number come from?".
One of the features that was advertised (mentioned in the iAPX 86, 88, 186 Microprocessors Part II book (July 1984)) was the ability to do exact arithmetic on integers up to 2^64, which is possible due to the 64-bit mantissa used in the 80-bit format.
- mortja 19d agoSo in a sense the 8087 was the first 64 bit CPU?
- matja 19d agoI wouldn't say so, because it was a co-processor: e.g., it depended on the 8086 to even generate addresses for memory operations. I think the IBM 7030 Stretch CPU (from 1964) would be a likely contender for being one of the first 64-bit CPUs.
- phire 19d agoAlso, even if ignored the fact that it was a co-processor, we don't generally count the width of the floating point and vector registers. Otherwise most modern CPUs would be labeled as either 256-bit or 512-bit. These days we generally label CPUs based on the width of the general purpose registers (though, it gets messy with things like the 68000). I personally suspect we won't ever see GPRs wider than 64 bits.
- kens 19d agoThe Cray-1 (1976) was probably the first 64-bit CPU.
- kragen 19d agohttps://en.wikipedia.org/wiki/64-bit_computing#64-bit_data_timeline https://en.wikipedia.org/wiki/64-bit_computing#64-bit_data_t... names Stretch from 01961 as the first natively 64-bit CPU, but maybe there are some that are even older?