Date: Wed, 20 May 1998 14:43:00 +0930 From: Greg Lehey <grog@lemis.com> To: Wilko Bulte <wilko@yedi.iaf.nl>, freebsd-hackers@FreeBSD.ORG Subject: Original PC (was: talk (fwd)) Message-ID: <19980520144300.M20476@freebie.lemis.com> In-Reply-To: <199805192157.XAA04150@yedi.iaf.nl>; from Wilko Bulte on Tue, May 19, 1998 at 11:57:14PM %2B0200 References: <199805191808.UAA17299@dorifer.heim3.tu-clausthal.de> <199805192157.XAA04150@yedi.iaf.nl>
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On Tue, 19 May 1998 at 23:57:14 +0200, Wilko Bulte wrote: > As Oliver Fromme wrote... >> In list.freebsd-hackers Mike wrote: >>> [...] >>> I've always heard (I have no motorola experience, yet) that motorola asm >>> blows x86 away when it comes to efficiency. A friend I have develops for >>> Be and he's always ranting about it. :) >> >> He's right. The x86 has 4 general-purpose registers, each of >> them 16 bits (they were extended to 32 bits in the 80386) and >> 4 address registers of the same size. And there are certain >> restrictions on their usage, e.g. you can only use the CX >> register as counter in the "loop" instruction etc. >> >> On the other hand, the Motorola 68k has 8 general-purpose >> registers of 32 bits and 8 address registers (also 32 bits). >> There is no restriction on their use, except that the 8th >> address regsiter is the default stack pointer. >> >> I programmed on both architectures in assembler, and I have to >> say that the 68k is definitely easier to program, and the >> higher number of registers allows for efficient programming. >> >> Maybe it was the biggest mistake ever made in computer history >> when IBM selected the 8088 for their first PC back in 1979. >> (Or was it 1978? Don't know, I probably couldn't even spell >> the word "Computer" correctly back then.) If they used the >> 68000 -- which was already available at that time -- we would >> have less problems today, I guess. > > An attractive (to me ;-) explanation is that IBM did not want to use the > 68K because it was a threat (performance wise) to their high profit machine > range. > > Urban legend or not, it sure sounds OK ;-) I just realized what this thread was about after deleting a lot of messages unread, so if I repeat something that has already gone past, please forgive me. Did it really take IBM so long to develop the PC? My recollection was that it was a sort of half-hearted effort after the devastating success of the 5100. In any case, the obvious reason for the choice of processor was the software available--CP/M 86 and 86-DOS for the 8088, nothing for the 68K. On top of that, the 8088 was cheaper because it had 8 bit memory (remember that most chips in those days were single bit). I don't think they had the slightest concern about attacking their mainframe machines, which were as fast as they needed to be (quite literally). Greg -- See complete headers for address and phone numbers finger grog@lemis.com for PGP public key To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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