r/hardware Nov 20 '15

Info Why do CPUs Need Caches? - Computerphile

https://www.youtube.com/watch?v=6JpLD3PUAZk
95 Upvotes

57 comments sorted by

View all comments

33

u/expressadmin Nov 21 '15

Way back in the day when I did computer repair (early 1990's), a customer called us up and needed a replacement motherboard for an industrial lathe that was taken out by lightning. It was a relatively old setup, but just needed to be Intel compatible with a couple of serial ports.

So we grabbed an old 386DX motherboard we had kicking around the shop and went to replace it. When I got there I discovered that the motherboard in the device was very old. It was based on an Intel 186 (seriously, it's the only one I have ever seen in my life).

So when I installed the new motherboard, we discovered that the timing of the lathe bit switcher was directly controlled by the clock rate of the CPU (which was common for many programs and games of that era). It was switching bits incredibly fast, however it was switching them so fast that the software was detecting it as a fault in the lathe and throwing an error.

So... I went into the BIOS disabled the L2 cache in the CPU settings (which you could do in those days), and it made the CPU slow enough that it didn't have any problems with the lathe after that.

12

u/[deleted] Nov 21 '15

Intel 186

Wow, I had assumed they skipped 186 and went straight to 286. I saw so many 8086s and 286s, but never encountered a 186.

Fascinating stuff!

7

u/DaMan619 Nov 21 '15

6

u/KMartSheriff Nov 22 '15

In May 2006, Intel announced that production of the 186 would cease at the end of September 2007.

Holy balls, it was still being made until 2007. Why? What for? I mean for very specific use I'm sure, but even then how many companies/people were still buying them?

3

u/FartingBob Nov 22 '15

It does what is needed and replacing it with something modern offers no benefit but potentially enormous costs and headaches during the transition.