Linked by Thom Holwerda on Thu 16th Aug 2018 20:51 UTC

Looking inside the Intel 8087, an early floating point chip, I noticed an interesting feature on the die: the substrate bias generation circuit. In this articleI explain how this circuit is implemented, using analog and digital circuitry to create a negative voltage.

Intel introduced the 8087 chip in 1980 to improve floating-point performance on 8086/8088 computers such as the original IBM PC. Since early microprocessors were designed to operate on integers, arithmetic on floating point numbers was slow, and transcendental operations such as trig or logarithms were even worse. But the 8087 co-processor greatly improved floating point speed, up to 100 times faster. The 8087's architecture became part of later Intel processors, and the 8087's instructions are still a part of today's x86 desktop computers.

A detailed and very technical article.

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Comment by smashIt
by smashIt on Fri 17th Aug 2018 11:41 UTC
Member since:

I've always been intrigued by how CPUs and more specifically ALUs are designed on a gate-level.
Can anyone recommend a good book on the subject?

Reply Score: 2

RE: Comment by smashIt
by JLF65 on Fri 17th Aug 2018 13:36 in reply to "Comment by smashIt"
JLF65 Member since:

Do you have the fundamentals? Start with boolean (digital) logic, and work up to CPUs. Look for tutorials on boolean logic like this one:

Work up to things like adders and latches. CPUs (simple ones at any rate) are merely groups of adders and latches and other similar logic elements.

I designed and built my own 4-bit MCU from TTL chips back in college - that was a load of fun I recommend to anyone interesting in computers. ;)

Reply Parent Score: 3

RE[2]: Comment by smashIt
by smashIt on Fri 17th Aug 2018 18:38 in reply to "RE: Comment by smashIt"
smashIt Member since:

Thanks for the reply.
I know my way around boolean algebra and de Morgan ;)
What I'm interested in is how they do things like division or multiplications (I'm pretty sure the won't just cascade a bunch of adders ;) )

Reply Parent Score: 2

RE: Comment by smashIt
by Vanders on Fri 17th Aug 2018 13:39 in reply to "Comment by smashIt"
Vanders Member since:

You'll be wanting Charles Petzold's Code: The Hidden Language of Computer Hardware and Software

Reply Parent Score: 4

RE: Comment by smashIt
by Cramit on Fri 17th Aug 2018 22:12 in reply to "Comment by smashIt"
Cramit Member since:

I really liked this course/book. It goes from nand and false to a computer, programming language, and os.

Edited 2018-08-17 22:12 UTC

Reply Parent Score: 2