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Intel 80386, a Revolutionary CPU

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Re: Intel 80386, a Revolutionary CPU

#171

Post by Aloha »

gumby wrote: post #166
Aloha wrote: post #154

Earlier quoted context omitted.

Making the microprocessor is just one challenge - you have to produce a workable system that someone wants to buy (aka, is cheaper or more attractive than the other options. It does appear that DEC could have made a single chip PDP-11 in 1980, and probably could have made one with an expanded address space to get around the memory limitations in the PDP-11. Intel did not do that, IBM in this case managed to - and it…

> I've never seen a claim that the 68000 significantly outperformed the 8086... I think you made a typo and meant 6800. Too late to edit though. I make this typo too because the 68k was such a significant chip in history.

No, I meant 68000 - what I'm trying to say is that while the 68000 is a significantly more elegant microarchitecture, had more functionality - and it did get to better performance faster, its not really any better in performance when judged on a clock for clock basis to the 8086.

Re: Intel 80386, a Revolutionary CPU

#172

Post by JPLeRouzic »

clausecker wrote: post #163
dboreham wrote: post #76

Earlier quoted context omitted.

I'm a big pdp-11 fan but this wouldn't have worked because 128K address space isn't enough even in 1975. Listen to Dave Cutler talk about this in the 3h long interview.

The PDP-11 had virtual memory in later models and could address more real memory than the 8086 afaik.

Are you sure the PDP-11 has virtual memory in later model?

They improved memory space because QBUS went from 64K (16 bits) to 256K (18 bits) to 4M (22 bits) but always usable only within a 64K window.

But I don't think it has way to resume instruction execution when encountering a memory trap.

You must be thinking of the VAX-11 where virtual memory was an explicit goal in its architecture (hence its name).

https://en.wikipedia.org/wiki/VAX

Re: Intel 80386, a Revolutionary CPU

#173

Post by [deleted] »

SomeoneFromCA wrote: post #159
varjag wrote: post #107

Earlier quoted context omitted.

1806VM2 wasn't released until late 1980s when there were numerous superior options, even if your yardstick is transistor count (but naturally not in USSR).

VM1 though appeared in 1983 and arguably BK home computer was the smallest ever PDP-11

[deleted]

Re: Intel 80386, a Revolutionary CPU

#174

Post by clausecker »

JPLeRouzic wrote: post #172
clausecker wrote: post #163

Earlier quoted context omitted.

The PDP-11 had virtual memory in later models and could address more real memory than the 8086 afaik.

Are you sure the PDP-11 has virtual memory in later model? They improved memory space because QBUS went from 64K (16 bits) to 256K (18 bits) to 4M (22 bits) but always usable only within a 64K window. But I don't think it has way to resume instruction execution when encountering a memory trap. You must be thinking of the VAX-11 where virtual memory was an explicit goal in its architecture (hence its name). https://en…

The PDP-11 has virtual memory with 8k pages. There are four address spaces of 64k each, one each for supervisor/kernel/user and for each of these text/data. This was extensively used with e.g. 2.11BSD to cram programs into the address space that are way too large for what the PDP-11 can do. And yes, that includes the ability to resume on memory trap.

You can read more on the Gunkies site: http://gunkies.org/wiki/PDP-11_Memory_Management

Re: Intel 80386, a Revolutionary CPU

#175

Post by snvzz »

userbinator wrote: post #59
cmrdporcupine wrote: post #52

Earlier quoted context omitted.

Imagine they got into making an ARM CPU competitive with Apple's? Or a server chip that is better than Ampera's, and sold at scale? I think they have the expertise and ability to do it.

A dual-mode ARM-x86 core would be an interesting CPU that they certainly have the skill to create. Thanks to the protected mode descriptor model, imagine having ARM64, ARM32, x86-32, and x86-64 code segments all coexisting in the same system, with no emulation nor virtualisation. There wouldn't be any overhead, because all instructions regardless of ISA get translated to uops anyway. They could add a RISC-V front-end…

I can see AMD/Intel releasing RISC-V CPUs with x86 acceleration.

I do not see it with an ARM mode, because there's no such software moat stuck on that platform as there is with x86.

Re: Intel 80386, a Revolutionary CPU

#176

Post by ack_complete »

pjmlp wrote: post #96
ack_complete wrote: post #62

Earlier quoted context omitted.

They do have lots of experience porting Windows to multiple platforms. They don't have very good experience managing the user experience of Windows transitioning between platforms. I was one of the early adopters of Windows on ARM, the Windows 10 native port to ARM64 (ARMv8). At release, practically the only native development tool was WinDbg -- neither Visual Studio nor Windows Performance Analyzer had been ported.…

Are you sure regarding ARM64EC? I doubt that they are dropping it any time soon, specially when they just announced the Arm Advisory Service.

They aren't dropping ARM64EC, it's still fully supported and how Visual Studio and Office run native. It is based on x64 emulation support, however, so it requires Windows 11. Snapdragon 835 is officially unsupported by Windows 11; 850 is conditionally supported, but IIRC at one point it didn't support hardware 3D acceleration in x64 apps.

Re: Intel 80386, a Revolutionary CPU

#177

Post by mixmastamyk »

cturner wrote: post #125

Intel evolved the x86 line beyond 386, into Pentium Pro and then to amd64. Why did Motorolla not do the same with the 68k? I have seen discussion that treats it as assumed knowledge that 68k was obsolete and needed to be replaced by powerpc. But it seems like conjecture - I have not seem technical arguments, and 68k seems like a cleaner architecture to ride forward than post-286 x86.

The problem wasn't technical, it was the lack of "buckets of money" that intel had access to, combined with customers that demanded backwards compatibility.

Intel tried at least twice to move them away to i860 or Itanic and failed. So, improve x86 was the winning bet.

https://news.ycombinator.com/item?id=37796469

Re: Intel 80386, a Revolutionary CPU

#178

Post by kjs3 »

Narishma wrote: post #169
kjs3 wrote: post #18

Maybe just me, but this sounds pretty revisionist wrt 'most important'. If the 8086/8088 hadn't stumbled into ubiquity via the IBM PC, there probably never would have been an 80286 much less an 80386. YMMV. That said...the 386 was a world-changing engineering achievement, and as much as I think in a just and fair timeline the 68030 would have taken over the world ( :-) ), you can't discount what Intel did.

The 386 maybe, but the 286 was already completed by the time the IBM PC launched if not before.

The IBM PC launched in mid 1981, which means the 8088 was fixed in the design at least, what, a year before if not more? The 286 shipped in 1984. Are you saying the 286 was a completed design in, say, 82-83, or that Intel was saying "this is what we think the 286 will look like" in that timeframe?

Re: Intel 80386, a Revolutionary CPU

#179

Post by Narishma »

kjs3 wrote: post #178
Narishma wrote: post #169

Earlier quoted context omitted.

The 386 maybe, but the 286 was already completed by the time the IBM PC launched if not before.

The IBM PC launched in mid 1981, which means the 8088 was fixed in the design at least, what, a year before if not more? The 286 shipped in 1984. Are you saying the 286 was a completed design in, say, 82-83, or that Intel was saying "this is what we think the 286 will look like" in that timeframe?

The 286 launched in early 1982, just a few months after the IBM PC. 1984 is when IBM put it in the PC AT.

Re: Intel 80386, a Revolutionary CPU

#180

Post by Gibbon1 »

jacquesm wrote: post #100
Gibbon1 wrote: post #79

Earlier quoted context omitted.

I read an essay by a guy that worked on project to produce a DEC minicomputer using ECL logic. And there was yet another group working on the DEC Alpha. At the time the main group was using most of the companies resources betting the company on dethroning IBM in the main frame arena. And was trying to stab the Alpha and Minicomputer group in the back. So probably not. Suspect IBM's skunk work project was done as a he…

Between x86 and the Alpha I much preferred the Alpha. Unfortunately it was wickedly expensive and it was hard to get. But for 64 bit work it was immediately usable and rock solid. It also beat Intel/AMD by about a decade to the market and I'm still kind of surprised that DEC managed to squander that lead.

I'm pretty sure if Motorola had rolled out the 68008 at the same time as the 68000 the 0x86 would be something few people remember. The hardware people choose the 8088 because it only required 8 DRAM's instead of 16.
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