The architecture flavor for the disassembler is defined by the asm.arch eval variable. You can use e asm.arch=?? to list all available architectures.
[0x00005310]> e asm.arch=??
_dAe _8_16 6502 LGPL3 6502/NES/C64/Tamagotchi/T-1000 CPU
_dAe _8 8051 PD 8051 Intel CPU
_dA_ _16_32 arc GPL3 Argonaut RISC Core
a___ _16_32_64 arm.as LGPL3 as ARM Assembler (use ARM_AS environment)
adAe _16_32_64 arm BSD Capstone ARM disassembler
_dA_ _16_32_64 arm.gnu GPL3 Acorn RISC Machine CPU
_d__ _16_32 arm.winedbg LGPL2 WineDBG's ARM disassembler
adAe _8_16 avr GPL AVR Atmel
adAe _16_32_64 bf LGPL3 Brainfuck
_dA_ _32 chip8 LGPL3 Chip8 disassembler
_dA_ _16 cr16 LGPL3 cr16 disassembly plugin
_dA_ _32 cris GPL3 Axis Communications 32-bit embedded processor
adA_ _32_64 dalvik LGPL3 AndroidVM Dalvik
ad__ _16 dcpu16 PD Mojang's DCPU-16
_dA_ _32_64 ebc LGPL3 EFI Bytecode
adAe _16 gb LGPL3 GameBoy(TM) (z80-like)
_dAe _16 h8300 LGPL3 H8/300 disassembly plugin
_dAe _32 hexagon LGPL3 Qualcomm Hexagon (QDSP6) V6
_d__ _32 hppa GPL3 HP PA-RISC
_dAe _0 i4004 LGPL3 Intel 4004 microprocessor
_dA_ _8 i8080 BSD Intel 8080 CPU
adA_ _32 java Apache Java bytecode
_d__ _32 lanai GPL3 LANAI
...
There are multiple options which can be used to configure the output of the disassembler. All these options are described in e? asm.
[0x00005310]> e? asm.
asm.anal: Analyze code and refs while disassembling (see anal.strings)
asm.arch: Set the arch to be used by asm
asm.assembler: Set the plugin name to use when assembling
asm.bbline: Show empty line after every basic block
asm.bits: Word size in bits at assembler
asm.bytes: Display the bytes of each instruction
asm.bytespace: Separate hexadecimal bytes with a whitespace
asm.calls: Show callee function related info as comments in disasm
asm.capitalize: Use camelcase at disassembly
asm.cmt.col: Column to align comments
asm.cmt.flgrefs: Show comment flags associated to branch reference
asm.cmt.fold: Fold comments, toggle with Vz
