Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!weretis.net!feeder1.news.weretis.net!news-peer.in.tum.de!news.belwue.de!news-zh.switch.ch!kanaga.switch.ch!switch.ch!newsfeed-00.mathworks.com!panix!not-for-mail From: Chris Jones Newsgroups: comp.arch Subject: Re: The Indexed Instruction Problem Solved! Date: Sat, 09 Jul 2011 16:21:11 -0400 Organization: PANIX Public Access Internet and UNIX, NYC Lines: 29 Message-ID: <87k4brurwo.fsf@panix.com> References: <4E1552A7.2020305@SPAM.comp-arch.net> <4E15545A.2090704@SPAM.comp-arch.net> NNTP-Posting-Host: c-24-60-101-244.hsd1.ma.comcast.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: reader1.panix.com 1310242872 14493 24.60.101.244 (9 Jul 2011 20:21:12 GMT) X-Complaints-To: abuse@panix.com NNTP-Posting-Date: Sat, 9 Jul 2011 20:21:12 +0000 (UTC) User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.2 (gnu/linux) Cancel-Lock: sha1:BGH/I2ACkD0Z4h6RmDta3sOOK4U= Xref: x330-a1.tempe.blueboxinc.net comp.arch:2447 EricP writes: > John Levine wrote: >>>> What other blasts from the past? VAX and M68K and NS32K... >>> Data General Nova: >>> 32k of 16 bit words (word address only). >>> lsb of address says whether referenced value is >>> 0=data or 1=indirect address (loop ad infinitum) >> >> The Nova was basically a souped up PDP-8 or PDP-9. DEC decided to use >> Gordon Bell's much more radical architecture for the 16 bit PDP-11, so >> designer Ed Decastro went off and started his own minicomputer >> company. [...] > I guess they were trying to offload operations > to memory due to the paucity of registers > (at least Nova was register challenged: > 4 accumulator registers + PC, SP, FP). The original Nova did not have a stack pointer (SP) or a frame pointer (FP). The Data General Eclipse (upward compatible with the Nova) did, available in memory in locations 40 and 41 (octal, as was natural with 15 address bits) respectively. There were added instructions to push and pop values to/from the stack, and to establish a frame on the stack after a subroutine call and to remove it and return from a subroutine (and analogous operations for entering and leaving an interrupt service routine on some Eclipses).