Ben's computer, pre- draft version 22-11-26

 Octal 77 is a simple 32 bit computer using MSI and LSI logic from 1977, using a
16 bit bus with up to 20 bits of address space. The bus speed about 1.5 mhz, for
a 80 x 25 Video Card (25Mhz). Two 2400 baud serial ports and two emulated 1.5
meg platter drives (SD cards) with 8 Kb BIOS and 96Kb ram are the standard sys-
tem. The octal front panel with Run/stop, adr/load, dep, exam, pc/ac,hi/low is
used to boot start the system.


 Internaly 3 512 x 8 proms are for the microcode. 2901 bit slices are used for
the data path, on two 16 bit cards. Programable logic like the 82S100 may be
used for microcode decoding in 1977. A current version could use CMOS 22V10's
or just 74HCTXX. 100 ns flash proms would be the only programable parts then.
Altera's DE1 Cyclone II, FPGA development system is used for prototyping the
TTL hardware.

 * Internal memory model

  32                16       8      1
 +-----------------+--------+--------+
 |                 |        |        | 6 GP registers A B C D X Y
 +-----------------+--------+--------+
 |                 |        |        | 4 GP optional registers E F G W .
 +-----------------+--------+--------+  ± extended flag or sign

                20                  1
 +------------+----+--------+--------+
 |------------|    .        .        | 2 special registers S PC
 +------------+----+--------+--------+

 [C] [R] [E]                           flags C carry R run E Enable IRQ

 * OP CODE FORMAT

  1 111 111
  6 543 210 987 654 321
 +-+---+---+---+---+---+
 |-|000|AAA|.SS|MM.|XXX|   MEM REF ST<SIZE> A <MODE> X  (EFA)=AC
 +-+---+---+---+---+---+
 +-+---+---+---+---+---+
 |C|OOO|AAA|.SS|MM.|XXX|   MEM REF OP<SIZE> A <MODE> X  AC = AC OP (EFA)
 +-+---+---+---+---+---+
 +-+---+---+---+---+---+
 |-|000|AAA|.00|000|###|   CTL                         CONTROL = NOP,HLT,DI,EI
 +-+---+---+---+---+---+
 +-+---+---+---+---+---+
 |-|000|AAA|.00|01±|###|   JSV A Z                     (-S) = PC, PC = #ADR
 +-+---+---+---+---+---+
 +-+---+---+---+---+---+
 |0|000|AAA|.00|10.|XXX|   LEA A X #                    AC = EFA
 +-+---+---+---+---+---+
 +-+---+---+---+---+---+
 |0|000|AAA|.00|11±|###|   LEA A Z                      AC = #ADR
 +-+---+---+---+---+---+
 +-+---+---+---+---+---+
 |C|OOO|AAA|.00|01.|XXX|   OP$ A X                      AC = AC OP IX (EXCESS 3)
 +-+---+---+---+---+---+
 +-+---+---+---+---+---+
 |C|OOO|AAA|.00|10±|###|   QUICK #                      AC = AC OP # QUICK
 +-+---+---+---+---+---+
 +-+---+---+---+---+---+
 |I|CCC|AAA|.00|11±|###|   BCC A #                      IF(CC) PC = #ADR
 +-+---+---+---+---+---+
 +-+---+---+---+---+---+
 |-|SSS|AAA|.01|00#|###|   SFT A #                      SFT AC #N TIMES
 +-+---+---+---+---+---+
 +-+---+---+---+---+---+
 |-|111|AAA|.10|00.|XXX|   JMP A R+                     PC = (R+)
 +-+---+---+---+---+---+
 +-+---+---+---+---+---+
 |-|111|AAA|.01|110|000|    SCC A                       A = CONDITION(CC)
 +-+---+---+---+---+---+

  * FUNCTION MATRIX

    A/X    OP  C   COND    SS      MM   SFT
   +-----+--------+-------+-------+----+---+
 0 |A  E | ST  -  |-      |REG   %|-R  |-  |
   +-----+--------+-------+-------+----+---+
 1 |B  F | -   XOR|Z      |BYTE  . -R  |SZL|
   +-----+--------+-------+-------+----+---+
 2 |C  G | SBX BIT|S      |SHORT :|R+,#|SCL|
   +-----+--------+-------+-------+----+---+
 3 |D  W | ADX AND|S+Z    |WORD   |R+,#|ROL|
   +-----+--------+-------+-------+----+---+
 4 |X  - | LD  OR |~C     |REG    |R # |ROR|
   +-----+--------+-------+-------+----+---+
 5 |Y  - | CAD CAC|~C+Z   |BYTE   |R # |SZR|
   +-----+--------+-------+-------+----+---+
 6 |S  - | SUB SBC|1      |SHORT  |Z   |SCR|
   +-----+--------+-------+-------+----+---+
 7 |#  - | ADD ADC|1      |WORD   |Z   |ASR|
   +-----+--------+-------+-------+----+---+

   * FRONT PANEL

 +---+---+---+---+---+---+
 | D | D | D | D | D | D | <run>    NIXIE TUBES
 +---+---+---+---+---+---+
 +---+---+---+---+---+---+
 |PHS|SSS|SSS|SSS|SSS|SSS| D X A R  PANEL AND FUNCTION SWITCHES
 +---+---+---+---+---+---+