4 ms·

Extended Zawinski's Law: "Every Instruction Set attempts to expand until it can read mail. Those Instruction Set which cannot so expand are replaced by ones wh

by forty 5y ago

Extended Zawinski's Law: "Every Instruction Set attempts to expand until it can read mail. Those Instruction Set which cannot so expand are replaced by ones which can." ;)

cmrdporcupine 5y ago
I feel like every instruction set eventually becomes VAX.
- CoastalCoder 5y ago
  Is it true that VAX allowed customers to extend the ISA themselves? I think I learned about that many years ago, but I couldn't find anything about that recently when skimming the 11/780 user manual.
  - jhgb 5y ago
    Was this about the KU780 option?
    - GeorgeTirebiter 5y ago
      Absolutely correct, KU780 was the Writeable Control Store described here http://bitsavers.trailing-edge.com/pdf/dec/vax/handbook/VAX_Hardware_Handbook_Volume_1_1986.pdf http://bitsavers.trailing-edge.com/pdf/dec/vax/handbook/VAX_... Sophisticated customers hacking the instruction sets of their machines goes back pretty much to the beginning. The earliest I personally know of is Prof Jack Dennis hacking MIT's PDP-1 to support timesharing, sometime in 1961. Commercial machines like the Burroughs B1700 had a WCS that was designed so various compiled languages could be optimized - e.g. a FORTRAN instruction set, a COBOL instruction set, etc https://en.wikipedia.org/wiki/Burroughs_B1700 https://en.wikipedia.org/wiki/Burroughs_B1700 It was also in the IBM360s because they had to emulate the IBM1401 software (although I don't know if the capability was open to users to modify). Today of course you have the various optional features of the RISC-V ecosystem --- easy to load up on an FPGA. Perhaps we should remember that we are in the very very early days of Computers, and we should expect continued modification / experimentation.
  - wrs 5y ago
    Yes. Search for “writable control store”. https://en.wikipedia.org/wiki/Control_store#Writable_stores https://en.wikipedia.org/wiki/Control_store#Writable_stores Here’s an example usage: http://hps.ece.utexas.edu/pub/gee_micro19.pdf http://hps.ece.utexas.edu/pub/gee_micro19.pdf

by forty 5y ago

Extended Zawinski's Law: "Every Instruction Set attempts to expand until it can read mail. Those Instruction Set which cannot so expand are replaced by ones which can." ;)

cmrdporcupine 5y ago

I feel like every instruction set eventually becomes VAX.

CoastalCoder 5y ago
Is it true that VAX allowed customers to extend the ISA themselves? I think I learned about that many years ago, but I couldn't find anything about that recently when skimming the 11/780 user manual.
- jhgb 5y ago
  Was this about the KU780 option?
  - GeorgeTirebiter 5y ago
    Absolutely correct, KU780 was the Writeable Control Store described here http://bitsavers.trailing-edge.com/pdf/dec/vax/handbook/VAX_Hardware_Handbook_Volume_1_1986.pdf http://bitsavers.trailing-edge.com/pdf/dec/vax/handbook/VAX_... Sophisticated customers hacking the instruction sets of their machines goes back pretty much to the beginning. The earliest I personally know of is Prof Jack Dennis hacking MIT's PDP-1 to support timesharing, sometime in 1961. Commercial machines like the Burroughs B1700 had a WCS that was designed so various compiled languages could be optimized - e.g. a FORTRAN instruction set, a COBOL instruction set, etc https://en.wikipedia.org/wiki/Burroughs_B1700 https://en.wikipedia.org/wiki/Burroughs_B1700 It was also in the IBM360s because they had to emulate the IBM1401 software (although I don't know if the capability was open to users to modify). Today of course you have the various optional features of the RISC-V ecosystem --- easy to load up on an FPGA. Perhaps we should remember that we are in the very very early days of Computers, and we should expect continued modification / experimentation.
- wrs 5y ago
  Yes. Search for “writable control store”. https://en.wikipedia.org/wiki/Control_store#Writable_stores https://en.wikipedia.org/wiki/Control_store#Writable_stores Here’s an example usage: http://hps.ece.utexas.edu/pub/gee_micro19.pdf http://hps.ece.utexas.edu/pub/gee_micro19.pdf