Hacker News Reader

Comment by Sharlin | Hacker News Reader

> because who would want to buy a Pentium Pro when the better-in-almost-every-way Pentium MMX

Maybe this was satirizing people running after every shiny new thing, but the MMX certainly wasn’t. The Pro was the first P6, a totally new, out-of-order microarchitecture that the Pentium 2 would be based on. The MMX was a standard P5 Pentium with a larger L1 and the MMX vector instruction set which, while the first of its kind in an x86, was ultimately not used much in applications, partly because it was integer-only (also because it awkwardly co-opted the existing FPU registers rather than having its own register file). In any case, the Pros were expensive and meant for business use, while the MMXs were consumer processors.

View on HN

Yes at that time Intel invented the market segmentation between "Pentium" for "consumers" and "Pentium Pro" for big spenders, and to make Pentium Pro more attractive they removed memory errors detection from the "Pentium" chipsets, which is the origin of the current state, when most non-server computers are very vulnerable to memory corruption and nobody can calculate how much money was lost by most computer owners during the last 3 decades, due to the greed of the Intel marketing, because nobody knows how many of the computer crashes or data loss cases that were typically attributed to unknown software bugs were actually caused by memory corruption.

Because this move was a money maker for all involved, all memory producers and also AMD followed immediately the Intel initiative. Memory modules without ECC would have never existed if adequate consumer protection laws had existed.

Yeah, the Pro and MMX were totally different market segments, not alternatives for each other. The Pro's competition at the time was DEC Alpha, PA RISC, etc. It wasn't a chip that made sense for ordinary PC users at the time.

Later, when Pentium MMX was eventually replaced by Pentium 2 for consumers, the successor of Pentium Pro was the first Intel Xeon CPU (which was a slightly enhanced Pentium 2, with bigger cache memory and with ECC memory).

The launch of Pentium Pro in 1995 was the moment when Intel segmented their CPU line into CPUs for consumers & server/workstation CPUs.

Just one caveat: the Pro overlapped in time with people running a lot of 16-bit code, and I think the Pentium MMX was faster for that, or at least that the Pro didn't offer much edge.

The pro did register renaming. But the way it worked, if you wrote to AX (16 bit write) and then read from EAX (32 bit read) it caused a pipeline stall from resyncing the registers.

Yeah, thanks both for elaborating!

Pentium Pro did out-of-order execution, Pentium MMX did not.

That’s what I said?

Reply on news.ycombinator.com