[HN Gopher] The Intel 8086 processor's registers: from chip to t...
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The Intel 8086 processor's registers: from chip to transistors
Author : chmaynard
Score : 100 points
Date : 2020-07-18 16:35 UTC (6 hours ago)
(HTM) web link (www.righto.com)
(TXT) w3m dump (www.righto.com)
| a1k0n wrote:
| Huh, it has 15 registers? AX, BX, CX, DX, SI, DI, BP, SP; CS, DS,
| ES, SS, IP, flags. What am I missing?
| gkolli wrote:
| I believe the status register (flag)
| kens wrote:
| There are two internal registers (IND and OPR) that aren't
| visible to the programmer. See the block diagram at the bottom
| of the post. The flags are in the ALU, not in the register
| file.
| Koshkin wrote:
| This is extremely fascinating. (Incidentally, Feynman's
| description of this technology in his _Lectures on Computation_
| is also well worth reading.)
| mjbrusso wrote:
| > The registers of the 8086 still exist in modern x86 computers,
| although the registers are now 64 bits.
|
| But they are logical (architectural) registers and are mapped at
| run time to one of the physical registers.
| supernova87a wrote:
| The other thing I'm interested to learn -- did the evolution of
| RAM proceed as kind of a "hand me down" technology from the CPU
| industry and basically tied to that?
|
| In that, I imagine memory is just about cramming more and more
| into the same space, and doesn't require the same complexity of
| innovation as CPUs (maybe some new developments in addressing,
| bus, or whatever) -- mostly just increasing the density and
| getting more storage locations in the same area?
|
| Or are there very interesting stories about RAM too? I do know
| some of the advances in hard disk magnetic breakthroughs, but
| silicon memory, not so much.
| kens wrote:
| Don't get me started on RAM. There's a whole lot of history
| there especially core memory.
|
| But to answer your specific question, Intel started off as a
| RAM company and their first product was a 64-bit (in total) RAM
| chip [1]. Processors were a sideline compared to the RAM market
| until the mid-1980s when Intel bailed out of DRAM as Japan took
| over.
|
| When Intel created a new chip process back then (HMOS through
| HMOS-III), they would first build a static RAM chip with the
| process. Once that worked, they would then use the process for
| microprocessors like the 8086.
|
| [1] http://www.righto.com/2017/07/inside-intels-first-
| product-31...
| rasz wrote:
| If you study to become MBA Intel memory business is its own
| separate case study
|
| https://www.gsb.stanford.edu/faculty-research/case-
| studies/i...
| retrac wrote:
| RAM came first. Even in the late 1960s, semiconductor SRAM was
| faster than core memory. Far more expensive, but faster. That
| created a market segment for caches and registers for high-end
| mainframes.
|
| DRAM quickly followed, and the 1103 DRAM of 1970, holding a
| total of 1024 bits, was Intel's first breakthrough product:
| https://en.wikipedia.org/wiki/Intel_1103
|
| DRAM and SRAM were already a multimillion dollar market by the
| time the first microprocessors came along a few years later.
| rasz wrote:
| DRAM requires incompatible fab steps to CMOS (probably also
| NMOS). This is one of the reasons you dont see much DRAM in
| CPUs or compute on ram.
| mmastrac wrote:
| Interesting discoveries. Perhaps some of the multi-port features
| on registers were for some of the REP features (ie: REP
| STOSB/MOVSB which updated multiple register) or some of the more
| generic instruction like PUSH/POP?
| supernova87a wrote:
| I'm really curious to know (as an amateur non-expert fan of chip
| hardware history, and local history) -- when Intel or Fairchild,
| etc. developed a new chip with whatever capabilities, how did
| they explain or get people to quickly understand what it could
| do?
|
| I haven't yet found a good popular level explanation of this,
| such as from reading https://en.wikipedia.org/wiki/Intel_8086. I
| see the technical info, but have no idea how I would know whether
| this is fundamentally amazingly better than what I have now, if I
| were in 1978 for example.
|
| How did they figure out who would be their customers? Did their
| customers have engineers who could look at a chip spec and see
| that it was 3x better on speed, power, etc? Did the chip
| designers have some use case in mind when designing, and those
| would be the first people sold to by the sales team?
|
| Was there a big sales effort needed for such new chips? or did
| they basically sell themselves?
| kens wrote:
| That's a big area to discuss. Yes, chip manufacturers had large
| sales departments. Magazines like _Electronics_ had articles
| discussing new chips (and other components) as well as lots of
| ads explaining the benefits of new products. (@TubeTimeUS posts
| a lot of these old ads on Twitter [1])
|
| Intel in particular put a huge effort into support tools for
| microprocessors (assemblers, libraries, development systems,
| documentation, etc). They worked closely with customers to get
| the chips adopted. For instance, "Operation Crush" was an
| effort to get customers to use the 8086 instead of the Motorola
| 68000.
|
| [1] e.g. A Zilog ad explaining the benefits of the Z-80:
| https://twitter.com/tubetimeus/status/1276912575913984001
|
| A long, interesting thread of component ads from 1967:
| https://twitter.com/TubeTimeUS/status/1280643791037140992
| gkolli wrote:
| For more info on Operation Crush, I rec. John Doerr's Measure
| What Matters. The beginning of the book outlines the intense
| competition Intel had with Motorola, Intel's strategy, and
| Andy Grove's sales/business philosophies.
| supernova87a wrote:
| Those ads are a trip! It looks to have been like the Cambrian
| explosion of every kind of chip manufacturer and chip type
| back then. It must have been very exciting, and very seat-of-
| your-pants time -- amazing to imagine.
| rasz wrote:
| Intel did it by hiring engineers with athletic backgrounds (aka
| more charismatic/better looking ones) and fast tracking them
| into marketing/sales departament :-)
|
| It was called 'Crush' :
| https://www.youtube.com/watch?v=xvCzdeDoPzg Enormous success.
| chongli wrote:
| _How did they figure out who would be their customers?_
|
| To some extent they didn't. They didn't think anyone would want
| the 4004, 8008, 8080 for computers. They started out marketing
| them for use in calculators. The personal computer market
| didn't exist yet. PCs were originally built by hackers, many of
| whom belonged to the homebrew computer club. The first one to
| go into production was the MITS Altair 8800, which used an
| Intel 8080, but when you bought it you got a bunch of chips you
| had to solder onto the board yourself, so only hackers had any
| interest in it.
|
| If you're really interested in this stuff, I highly recommend
| the book _Hackers: Heroes of the Computer Revolution_ by Steven
| Levy [1]. The book traces the history of hackers from its
| beginnings at the tech model railroad club at MIT through the
| homebrew computer club at Stanford, and on into the beginnings
| of the computer game industry. It's a fantastic chronicle of
| some very interesting and entertaining characters, with some
| real pranksters in the bunch. A very fun read!
|
| [1]
| https://en.wikipedia.org/wiki/Hackers:_Heroes_of_the_Compute...
| kps wrote:
| The 4004 was designed for calculators. The 8008 was for a
| terminal, the CTC Datapoint 2200, and Intel (and TI)
| implemented _their_ instruction set... and that 's why today
| x64 FLAGS has PF.
| the-dude wrote:
| The first 'computers' ( Babbage? ) were deemed interesting
| because they could calculate sin-tables for example. Lots of
| those tables still contained errors because they were
| calculated by humans.
|
| Faster horse and all.
| acqq wrote:
| > no idea how I would know whether this is fundamentally
| amazingly better than what I have now, if I were in 1978 for
| example.
|
| For the start you should define what role you imagine you had
| in 1978.
|
| Do you imagine working in some company that should decide which
| CPU to use for their new computer? Then the decisions were made
| exactly like now: you'd first consider the options with which
| you are more familiar, of for which you already had something
| "prepared." Second, you'd also want to avoid the option for
| which you have learned it has some weaknesses.
|
| That's what moved the people in charge of building the first
| IBM PC, for example. They had experience with Intel, and also
| experience with developing using Intel chips.
|
| In his previous post Ken linked to the text "A Personal History
| of the IBM PC" by David Bradley:
|
| https://dl.acm.org/doi/10.1109/MC.2011.232
|
| The text is very informative, but behind a paywall.
|
| Here's a TED talk by him too, which has the context explained
| for the public who aren't professionals, also nice it its own
| way:
|
| https://www.ted.com/talks/dr_dave_bradley_how_did_ibm_create...
| supernova87a wrote:
| Thanks for that!
|
| If you search for the following link on your favorite
| scientific paper illegal sharing site, it's available as PDF:
| https://ieeexplore.ieee.org/document/5984815
| mhh__ wrote:
| If you're selling to business customers you just need to
| demonstrate value, it doesn't have to be technical e.g. "Our
| new generation of chips will save you a dollar in power while
| finishing in half the time" etc.
|
| Computing hasn't changed all that much since then, people
| haven't at all: for those in the know we have benchmarks, for
| those who don't we have regular marketing.
| weinzierl wrote:
| > I'm really curious to know (as an amateur non-expert fan of
| chip hardware history, and local history) -- when Intel or
| Fairchild, etc. developed a new chip with whatever
| capabilities, how did they explain or get people to quickly
| understand what it could do?
|
| Apart from what other comments already correctly stated, the
| more straightforward answer to your questions is probably: They
| did and they do develop and build reference designs. Take any
| silicon you can buy today and very likely you will find a
| detailed reference design in the data sheet. These designs
| don't exist only on paper, they are built and used for
| demonstration purposes and sales. As a customer often you can
| buy what is basically the reference design in form of
| evaluation boards too.
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