The Perfect Computer - 36 bits?
|
From: John Ahlstrom on 27 Mar 2007 16:26 Andrew Swallow wrote: > David Kanter wrote: > [snip] > >> >> A much more reasonable, and possibly true, assertion would be that the >> advantage of RISC architectures decreased over time. However, even as >> late as the Pentium 1, there was a huge advantage for RISC >> architectures. With the Pentium Pro that became less clear, although >> RISCs still ruled the roost for FP heavy applications. > > We can certainly have a nice debate as to whether anything containing > floating point hardware is RISC. > > Andrew Swallow From > ====REPOST==== > Article 22850 of comp.arch: > Path: mips!mash > Subject: Nth re-posting of CISC vs RISC (or what is RISC, really) > Message-ID: <2419(a)spim.mips.COM> -- snip snip > MOST RISCs: > 3a) Have 1 size of instruction in an instruction stream > 3b) And that size is 4 bytes > 3c) Have a handful (1-4) addressing modes) (* it is VERY > hard to count these things; will discuss later). > 3d) Have NO indirect addressing in any form (i.e., where you need > one memory access to get the address of another operand in memory) > 4a) Have NO operations that combine load/store with arithmetic, > i.e., like add from memory, or add to memory. > (note: this means especially avoiding operations that use the > value of a load as input to an ALU operation, especially when > that operation can cause an exception. Loads/stores with > address modification can often be OK as they don't have some of > the bad effects) > 4b) Have no more than 1 memory-addressed operand per instruction > 5a) Do NOT support arbitrary alignment of data for loads/stores > 5b) Use an MMU for a data address no more than once per instruction > 6a) Have >=5 bits per integer register specifier > 6b) Have >= 4 bits per FP register specifier Debate over? JKA
From: Rich Alderson on 27 Mar 2007 17:56 nmm1(a)cus.cam.ac.uk (Nick Maclaren) writes: > The PDP-11 never made much impact as a 'general' computer, especially > in the commercial arena, whereas the PDP-10 and PDP-20 did. Point of order: There is no such thing in the DEC/Digital product line as a "PDP-20". The highest number in the PDP series was the PDP-16. Some people believe that if the PDP-10 ran Tops-10, then a machine running Tops-20 must be a PDP-20, but the reasoning is flawed. Modulo some differences in I/O, either operating system will run on the same hardware. I call to your attention the bright orange box labeled "DECSYSTEM-20" on which I run Tops-10 for the PDPplanet project (http://www.pdpplanet.org/). -- Rich Alderson | /"\ ASCII ribbon | news(a)alderson.users.panix.com | \ / campaign against | "You get what anybody gets. You get a lifetime." | x HTML mail and | --Death, of the Endless | / \ postings |
From: Peter Flass on 27 Mar 2007 18:22 Nick Maclaren wrote: > > It is a great pity that the new RISC systems (as distinct from previous > inventions of the approach) concentrated entirely on making the hardware > simple, often at the cost of making the software hell to get right. > Which is one of the reasons that many aspects of modern software are > so much worse than they were 25 years ago. > I, as a programmer, shouldn't have to worry about ordering the instructions so as not to lose cycles (pipeline slots, whatever.) That's what hardware/microcode is for.
From: Peter Flass on 27 Mar 2007 18:23 jmfbahciv(a)aol.com wrote: > > And I'm telling you, again, that DEC did not have the infrastructure > to handle that support. DEC's main business was not retail-ish. > Even IBM decided they didn't want to be in this business.
From: Peter Flass on 27 Mar 2007 18:27
Nick Maclaren wrote: > |> Yeah I seem to recall there being a couple of PDP11s hooked to a > |> 370 in the early 1980s (and late 1970s) not far from you. > > Yup :-) And we weren't the only such site, because those mainframes > were dire for single-character interactions and related communications > work and peripheral driving. > Series-1's were also in this market. IBM sold them with an IUP as a terminal driver. "Yale ASCII" or something like that. |