The BLIZZARD computer architecture

Ronald L. Rivest
1979 SIGARCH Computer Architecture News  
He present a simple and po#lerful computer architecture Hith several novel feat~lreq, the most interesting of t4hich are probabty the Hays in ~.lhich imnlectiate and stack operands are treated in this register-oriented machine. The recent debate in this journal (see [1]-[5]) over the relative eff ciencies of stacks ;md registers wilt take on a ne~.~ form for the BLIZZARD, lhe machine is called the BLIZZARD, since the design r4as initiated ~4hi le the author" iJas snot4-bound at home during the
more » ... at home during the Boston "Blizzard of '78". A summ~.-g of the BLIZZARD's features are: flemor U consists of up to 2**32 1G-bit words. Addressing is by 14or(t. lg rtotzhle-Hord registers are available, Seven have special functions (like PC, SP): three of the seven are "~Jindou" registers for fetching immed}atr' immediate operands and pushing/popping stack operands. -Data len[Iths ], 2, 4, 8, lg or 32 bits (called bits, dabs, nibs, hutes, ~or'ds, ~md doubte-I.Iords, or genericallg, "flakes") hanctled easil U. Small flakes are stored as packed arrags: each flake is easilg accessible, -Each instruction is one 14orcl long (and is possiblg followed b 9 ~lord or double-l.rord immediate operands) and has a simple four-nib format, -There are looping, subroutine enter/exit, and block move instructions, etc, I . NOTATIr]N AND DATA FORrlATS A rJouble-~4ord occupies consecutive ~Jords; its address is the same at:. the t~ord rJith lower address (which contains the least-significant bits of the double-iIord), IJe let [X] denote the contents of the memor9 ~Jor(I at location X, and (X) denote the double-word stored at location X (consisting of IX] and [X+t]). He also use () for denoting register contents: (PC}, etc. Integers are in tt4o's-complement; floating-point numbers are double . words t4ith a sign, eight exponent bits (excess 128.code) and a 23-bit mantissa, lJe use hexadecimal notation: a 14ord is four hex digits (nibs). A he× constant appears as # folios.ted b9 a nib sequence, Lower case letters denot~ arhitraru nibs: flBABd is a word with nibs 8, A, B, and an arbitrar9 nib d. The bits of a double-~Jord or word are numbered from 31 or ]5 for the sign bit to 0 for the least-significant bit. Similarl9, flakes in a word are numbered starting with zero for the flake in the least-significant position. II. RE61SfERS BLIZZARD's IG double-word registers (R8 to RF) are careful l9 al located bettleen seven dedicated uses and general-purpose use. This frees the opcodes from having to specifg operand sources (e.g. immediate, stack, or register}. The registers are identified with double-words 8 to F of memor9 (Ri consists of memorg ~4ords 2. i and 2,i+1). RO
doi:10.1145/859500.859501 fatcat:53xc2i5bbnbwdj3alhkwktzlyu