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Change bold code snippets to inline code blocks

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James Gregory 2013-12-31 17:12:29 +11:00
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20
11-05.md
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@ -12,7 +12,7 @@ pages: 220-222
Under ideal conditions, a 286 can access memory much, much faster than
an 8088. A 10 MHz 286 is capable of accessing a word of system memory
every 0.20 ms with **REP MOVSW**, dwarfing the 1 byte every 1.31 µs that
every 0.20 ms with `REP MOVSW`, dwarfing the 1 byte every 1.31 µs that
the 8088 in a PC can manage. However, access to display memory is
anything but ideal for a 286. For one thing, most display adapters are
8-bit devices, although newer adapters are 16-bit in nature. One
@ -29,7 +29,7 @@ factors that reduce the speed with which the 286 can access display
memory. Far more cycles are eaten by the inherent memory-access
limitations of display adapters—that is, the limited number of display
memory accesses that display adapters make available to the 286. Look at
it this way: If **REP MOVSW** on a PC can use more than half of all
it this way: If `REP MOVSW` on a PC can use more than half of all
available accesses to display memory, then how much faster can code
running on a 286 or 386 possibly run when accessing display memory?
@ -97,17 +97,17 @@ programs are still limited to 1 MB of addressable memory on the 286. In
either mode, each segment is still limited to 64K.)
There are also a handful of 286-specific real-mode instructions, and
they can be quite useful. **BOUND** checks array bounds. **ENTER** and
**LEAVE** support compact and speedy stack frame construction and
they can be quite useful. `BOUND` checks array bounds. `ENTER` and
`LEAVE` support compact and speedy stack frame construction and
removal, ideal for interfacing to high-level languages such as C and
Pascal (although these instructions are actually relatively slow on the
386 and its successors, and should be used with caution when performance
matters). **INS** and **OUTS** are new string instructions that support
efficient data transfer between memory and I/O ports. Finally, **PUSHA**
and **POPA** push and pop all eight general-purpose registers.
matters). `INS` and `OUTS` are new string instructions that support
efficient data transfer between memory and I/O ports. Finally, `PUSHA`
and `POPA` push and pop all eight general-purpose registers.
A couple of old instructions gain new features on the 286. For one, the
286 version of **PUSH** is capable of pushing a constant on the stack.
286 version of `PUSH` is capable of pushing a constant on the stack.
For another, the 286 allows all shifts and rotates to be performed for
not just 1 bit or the number of bits specified by CL, but for *any*
constant number of bits.
@ -143,5 +143,5 @@ complex 386-specific instructions are slower than equivalent sequences
of simple instructions on the 486 and especially on the Pentium.) What's
more, both old and new instructions support 32-bit operations on the
386. For example, it's relatively simple to copy data in chunks of 4
bytes on a 386, even in real mode, by using the **MOVSD** ("move string
double") instruction, or to negate a 32-bit value with **NEG eax**.
bytes on a 386, even in real mode, by using the `MOVSD` ("move string
double") instruction, or to negate a 32-bit value with `NEG eax`.