Intel Pentium: A Bothersome Bug
Source: Tom's Hardware – Keywords: intel, cpu, history
Intel Pentium: A Bothersome Bug
The Pentium, introduced in 1993, was interesting for more than one reason. It was the first x86 to drop the traditional model number for a more attractive name, since Intel wasn’t allowed to trademark a name made up of numbers only. It’s also famous because of a bug it contained. On the first generations of Pentiums, certain division operations produced an incorrect result. Intel replaced the processors, but the damage was done. A very rare error gave rise to the first big IT media buzz.
The Pentium was sold in three different versions, the first without a CPU multiplier, the second with a multiplier (including the very familiar Pentium 166), and the last with the SIMD instruction set for x86s, MMX. The Pentium MMX also increased the size of the Level 1 cache and brought in a few minor improvements. This was the first Intel x86 capable of executing two instructions in parallel. The L2 cache was on the motherboard with these processors (running at the frequency of the FSB).
| Code name | P5, P54 | P55 (Pentium MMX) |
| Date released | 1993 | 1997 |
| Architecture | 32 bits | 32 bits |
| Data bus | 64 bits | 64 bits |
| Address bus | 32 bits | 32 bits |
| Maximum memory | 4096 MB | 4096 MB |
| L1 cache | 8 KB + 8 KB | 16 KB + 16 KB |
| L2 cache | Motherboard (FSB frequency) | Motherboard (FSB frequency) |
| Clock frequency | 60-200 MHz | 133-300 MHz |
| FSB | 50-66 MHz | 60-66 MHz |
| FPU | on chip | on chip |
| SIMD | no | MMX |
| Fabrication process | 800-600-350 nm | 350 nm |
| Number of transistors | 3.1-3.3 million | 4.5 million |
| Power consumption | 8-16 W | 4-17 W |
| Voltage | 5 V-3.3 V | 2.8 V |
| Die surface area | 294-163-90 mm² | 141 mm² |
| Connector | Socket 4, 5 or 7 | Socket 7 |
Here’s a little explanation of the Pentium bug: certain calculations using the FPU resulted in erroneous results. This was fairly rare—though sources disagree about exactly how rare—and Intel replaced the defective processors free of charge. Here’s an example of a Pentium error:
4195835.0/3145727.0 = 1.333 820 449 136 241 002 (correct result) 4195835.0/3145727.0 = 1.333 739 068 902 037 589 (incorrect result on a defective Pentium)
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Wasn’t one of the key features of the Pentium Pro line of processors the increase in IRQs to 256 rather than the 16 of the previous generations?
In the days of virtual IRQs assigned by windows it's easy to forget the headache of trying to install multiple interface cards without running out of resources.
am I mistaken? or the Maximum memory figures are wrong? 4096MB or is it KB on 386, 486 and Pentium MMX class CPU's. and 64MB on P-II and so on.
Modern Intel CPU: P1-> P3 -> P4M -> C2D -> C2Q
Modern AMD CPU: P1(Intel) -> P3(Intel) -> K8 -> K10
Next gen CPU: Modified P1
The Pentium 1 & 3 are possibly the most widely base processor in modern computing. Even AMD's chips are based on them.
Hmm....
Interesting...AMD chips based on P3... EHEHEHEHHEHEHE
I think you need a...khhmmm...LIFE
cheers
Nice article that made me a little bit misty-eyed and nostalgic (being of the original 8086 generation)
Did a bit of a clear-out of my parts boxes not so long ago and found a couple of PPro's, a 486DX2/66, a 386SX and a 386DX. Threw them out but perhaps should have built a little shrine? ;p
Cheers.
There are some errors in the article, Pentium M Dothan had a 2.26GHz model which is not mentioned there, they had a VCore of 1.356V and a TDP of 27W, not 36W like stated here, also it's die size is 88mm2, not 87mm2, it also came as a socket 478 which was incompatible with the Pentium 4 socket 478 due to it's electrical differences.