128-bit processors: Why we may not need them until 2043
The Prospects for 128 Bit Processors ( John Mashey SGI 1995)
In a 1995 Usenet post, John Mashey of Silicon Graphics analyzed the prospects for 128-bit processors, predicting they wouldn't be needed until around 2043 based on physical memory growth, or possibly 2020 if virtual memory pressure grows faster. He noted that 64-bit CPUs are likely sufficient for a long time, and that the transition from 64 to 128 bits would take twice as long as from 32 to 64 bits, given DRAM density trends.
64-bit CPUs are likely to be sufficient for a *long time*; Note that there are already <$35 64-bit micros available, so this is not exotica.
- kev009
One interesting thing with wider addresses isn't necessarily increasing itself, but features built upon the expansion. CHERI is one example of that.
- A1kmm
So reflecting on that, I think the core assumption that didn't pan out is that the memory / CPU ratio will grow because we'll need more memory, hence requiring CPUs to address more than 16 EiB of data (16 EiB = 16384 PiB = 16777216 TiB of data, what 64 bits can address).
But in practice, we've produced a lot more compute. The memory / CPU ratio has increased, but most growth has been from more CPUs (and generally not shared-memory ones, but ones with their own completely separate memory space).
IPv6 is 128 bit, so we do have 128 bit ways of addressing computers, but I'd say we're still a long way from a CPU needing to address that much memory as a common case. The speed of light limits how far away memory can be from the CPU for good performance, so short of some drastically new memory technology, it seems unlikely we'll need it soon for any ordinary type of computing device.
- Aardwolf
Personally I'm disappointed 128-bit floating point (quadruple precision) never properly made it into CPU's (sure it appeared in some niche ones here and there, but not in what we actually use today). After all, in the 1980's they had 80-bit ones, it's not even that far off, and they had millions times less transistors then.
While probably niche and applications that need higher precision using their own custom types anyway, they'd allow cool stuff like easy to program fractals with much higher detail than now. But also, less precision loss in many applications.