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About LinkBacksI am just having a debate with a friend and was wondering do intel Use Risc or Cisc??
I am just having a debate with a friend and was wondering do intel Use Risc or Cisc??
Pretty sure Intel x86 is CISC
moving to hardware
Last edited by Agent; 14-12-2004 at 08:34 PM.
Originally Posted by Saracen
It's not as simple as RISC vs CISC. x86 code is CISC, but IIRC the Pentium and other modern x86 processors translate x86 into RISC-style instructions for internal processing.
http://www.tomax7.com/aplus/APlusCD/...0vs%20RISC.docx86
An important factor is also that the x86 standard, as used by for instance Intel and AMD, is based on CISC architecture. X86 is thé standard for home based PC's. Windows 95 and 98 won't run at any other platform. Therefore companies like AMD an Intel will not abandoning the x86 market just overnight even if RISC was more powerful.
Changing their chips in such a way that on the outside they stay compatible with the CISC x86 standard, but use a RISC architecture inside is difficult and gives all kinds of overhead which could undo all the possible gains. Nevertheless Intel and AMD are doing this more or less with their current CPU's. Most acceleration mechanisms available to RISC CPUs are now available to the x86 CPU's as well.
Interesting read. Havnt really read into it before, only remember the small bits i did from college days.
http://www.amigau.com/aig/riscisc.html
Looks interesting too.
Intel use both.. muchly depends on the chips though as Intel do other non PC x86 chips that are more Risc based i.e. StrongArm processors.
But mostly they are designs licensed from Arm.com
Here's a ickle pic of all the companies logo's that are using ARM designs or there own chips..
http://www.arm.com/images/community-all.jpg
you'll notice Intel in there
No AMD there, interesting to see BitBoys on there though
Salazaar : <Touching wood as I write this...>
The StrongArm was originally a Digital/ARM collaboration, and Intel bought into it when they purchased Digital. They've developed it since but they sort of ended up with it by accident rather than design. This would be back in 1996 or so, just before the explosion in mobile phones, STBs and other devices using ARM chips. Just to think I had a lovely ARM2 based machine back when ARM were just Acorn's chip-designing division, and cut my coding teeth on ARM code. ARM formed from Acorn, Apple and VLSI back in 1990. Apple's holding in ARM helped keep them solvent, as they sold off chunk after chunk through the late 90s realising lots of dough.
I use Sparc and Risc in my sun's and Hp's.
My laptop and desktop are P4's and X86 servers are opterons or itaniums
It is Inevitable.....
xeons, not itaniums
sorry
It is Inevitable.....
Ok to answer the original question as best I can, long answer but bear with me:
Originally x86 chips were CISC, and they sort of pre-date the philosophy behind RISC, but that's all it is, a sort of philosophy of design, rather than a clear, yes or no definition. These days x86 processors incorperate some of the RISC philosophy and vice versa.
The idea behind risc came from research that showed that something like 80% of called instructions in code, used only 20% or so of a CPU's available instructions. So why not produce a chip that only does those important instructions, but highly optimised to run very fast. Other instructions, when needed, can be emulated using these existing ones. Hence the name (Reduced Instruction Set Computer - RISC)
The other philosophy of Risc was to have lots of registers, which accept as input, or store as output, a byte of data, or instruction or whatever on the way into or out of the chip. I think that comparable early ARM chips had about 15 or so user programmable registers, (Zathras can you confirm?) when x86 chips had only about 4. The upshot of this is that a data result can be left on a register and then loaded straight back into the processor in another instruction without resorting to memory or even cache, very fast.
These days however I belive that modern CISC processors have lots of registers, and modern RISC chips often have much larger instruction sets than their ancestral processors would have had (although not allways).
<And Breathe
So modern x86's are CISC with some RISCish features, however as pointed out earlier, Intel have licensed various ARM designs (RISC) such as the intel X-Scale which is basically a Strong-Arm. Hence the lastest Risc-OS machines (Acorns of sorts) run on Intel processors
The above post is provided without warrenty, actual or implied, to make any sense, be at all accurate, complete or even true. It was all dredged from the back of my brain from long systems-architecture lectures at Uni and my own experiences with Acorn computers (maytheyrestinpeace).
They told me I was gullible ... and I believed them.
PS don't confuse your Registers (CPU) with your Registrys (Windose)
They told me I was gullible ... and I believed them.
Remembering a tidbit of information Stoo once handed out on a train platform in London, I seem to recall that the Pentium Pro was rather RISCish.
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ARM processors have fifteen registers and a program counter
Yay! Am I also right in recalling that ARM processors don't (or didn't) have any floating-point arithmatic functions, and all float arythmatic was emulated using integers - slowly IIRC. this meant that ported code that was pretty much just re-compiled from a PC to an Acorn tended to crawl, but if it was re-written only using ints, it flew.
They told me I was gullible ... and I believed them.
HP (not Intel) bought Digital, IIRC.
Intel "bought" Digital's fab plant and most of the chip development as part of a settlement for patents breach, including a whole set of conditions about having to manufacture Alphas for a certain timescale. This also gave them a large amount of the StrongArm dev team, hence their uptake of the chip. The remainder of DEC (not much left) was sold to Compaq who then became HP.
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