> From: Danny Mayer <ma...@ntp.org> USENET newsgroup comp.protocols.time.ntp\)" <questions.lists.ntp.org> > List-Unsubscribe: <https://lists.ntp.org/mailman/listinfo/questions>, > <mailto:questions-requ...@lists.ntp.org?subject=unsubscribe> > List-Archive: <https://lists.ntp.org/pipermail/questions> > List-Post: <mailto:questions@lists.ntp.org> > List-Help: <mailto:questions-requ...@lists.ntp.org?subject=help> > List-Subscribe: <https://lists.ntp.org/mailman/listinfo/questions>, > <mailto:questions-requ...@lists.ntp.org?subject=subscribe> > Content-Type: text/plain; charset="us-ascii" > Content-Transfer-Encoding: 7bit > Sender: questions-bounces+oberman=es....@lists.ntp.org > Errors-To: questions-bounces+oberman=es....@lists.ntp.org > X-Proofpoint-Virus-Version: vendor=fsecure > engine=1.12.8161:2.4.5,1.2.40,4.0.166 > definitions=2009-07-28_09:2009-07-24,2009-07-28,2009-07-28 signatures=0 > X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 > ipscore=0 phishscore=0 bulkscore=0 adultscore=0 classifier=spam adjust=0 > reason=mlx engine=5.0.0-0811170000 definitions=main-0907280208 > X-Regulatory-Partner: 1 > > David Woolley wrote: > > Richard B. Gilbert wrote: > > > >> ISTR reading that the Intel 80x86 line was CISC on top and RISC > >> underneath. I couldn't swear to it though. All I ever saw or worked > >> with was the CISC part of it. > > > > I think that pretty much defines CISC. CISC machines are normally > > micro-program driven machines. > > They didn't used to be. However, with the VAX 8600, for example, the > instruction set was implemented in microcode. So were the diagnostics > for that matter.
True. but that was before the time of most of the readers here. Most CISC processors after about 1972 were micro-engine based. the original PDP-11 was not, but it was soon re-engineered as the PDP-11/20 with a micro-coded processor. The PDP-11 was the last non-micro-coded system from Digital. IBM went to micro-coded systems for their main-frames about the same time as did most others. So, while CISC could be done without a micro-engine, it was onlhy the earliest of the CISC mechines that did so. All VAX systems had micro-engines including the origianl 11/780 and 11/750. Most systems before the late 60's were effectively RISC, although no one called them that. The PDP-8 instruction set was 8 basic commands, AND, TAD, ISZ, DCA, JMS, JMP, IOP, and OPR. The OPR instructions were, effectively, a micro-engine of 19 slightly more complex instructions, but all were implemented in very simple DTL logic and none took more than a single cycle and the full 27 insgtructions were simpler than most RISC processors. -- R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: ober...@es.net Phone: +1 510 486-8634 Key fingerprint:059B 2DDF 031C 9BA3 14A4 EADA 927D EBB3 987B 3751 _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
