Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!think.com!snorkelwacker.mit.edu!stanford.edu!neon.Stanford.EDU!torrie From: torrie@cs.stanford.edu (Evan Torrie) Newsgroups: comp.sys.amiga.advocacy Subject: Re: The 68050 - end of the 680x0? (was Re: The Amiga's Future) Message-ID: <1991Jun22.065702.24890@neon.Stanford.EDU> Date: 22 Jun 91 06:57:02 GMT References: <5068@orbit.cts.com> <16647@darkstar.ucsc.edu> < <1308@cbmger.UUCP> <28@ryptyde.UUCP> > <01dH!cmr@cs.psu.edu> <1991Jun10.072945.8821@neon.Stanford.EDU> <22365@cbmvax.commodore.com> <1135@stewart.UUCP> <1147@stewart.UUCP> Sender: torrie@neon.Stanford.EDU (Evan James Torrie) Organization: Computer Science Department, Stanford University, Ca , USA Lines: 47 jerry@polygen.uucp (Jerry Shekhel) writes: >daveh@cbmvax.commodore.com (Dave Haynie) writes: >> >>The unified cache is an obvious example >>of this -- Intel's even using split caches themselves in their other chips, >>because they simply result in better performance. >> >Are you suggesting that the unified cache is a limitation designed to ensure >MS-DOS compatibility? How would a split cache break MS-DOS? MS-DOS used to [still does?], and various MS-DOS-based programs, make use of self-modifying code. In a split cache environment, any self-modifying code immediately falls over in a screaming heap, because any "code" modifications are reflected only in the data cache, not in the instruction cache. In my opinion, this was evidently a major, major compromise on the part of Intel to accomodate backward compatibility with MS-DOS, since as Dave notes, Intel's other microprocessors [along with Motorola and the RISC manufacturers] use split I/D caches. >> >>Yet, the 486SX, at least presently, costs the same to make as the 486, since >>it's the same die. They're selling, as always, based on their captive market. >> >I agree. Actually, I'd bet that the 486SX costs less to produce, since the >yield is probably much greater. I wouldn't be surprised if a large part of >486SX production consisted of reject 486 chips that failed the speed test or >ended up with defective FPUs. According to EE Times, _all_ of the 486SX production consists of real 486 chips with the FPU disabled. (Apparently, a real 486SX die won't be fabricated until the end of the year). In the meantime, you could also buy a 487SX, which just happens to be yet another real 486, this time with everything BUT the FPU disabled. So for more than the price of a single 486, you get to buy TWO castrated 486s, which together run slower than the single 486. Is it any wonder Intel is despised by so many?? -- ------------------------------------------------------------------------------ Evan Torrie. Stanford University, Class of 199? torrie@cs.stanford.edu "Lay me place and bake me pie, I'm starving for me gravy... Leave my shoes and door unlocked, I might just slip away - hey - just for the day."