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Old February 25th 14, 12:41 AM posted to comp.sys.intel,comp.sys.ibm.pc.hardware.chips,alt.windows7.general
Jason[_13_]
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Posts: 10
Default How many x86 instructions?

On Mon, 24 Feb 2014 12:11:05 -0800 "Gene E. Bloch"
wrote in article leg90r$nln$1
@news.albasani.net

On 2/23/2014, Yousuf Khan posted:
On 23/02/2014 6:15 PM, BillW50 wrote:
On 2/23/2014 4:41 PM, charlie wrote:
The front panel on many of the old mainframes and minicomputers
allowed
direct entry of machine code, and was usually used to manually
enter
such things as a "bootstrap", or loader program.

The way I recall is any computer only understands machine code and
nothing else. Anything else must be converted to machine at some
point.


I know what Charlie is talking about. When he talks about directly
entering machine code, it means typing in the binary codes directly,
even without niceness of an assembler to translate it partially into
English readable. This would be entering numbers into memory
directly, like 0x2C, 0x01, 0xFB, etc., etc.


Yousuf Khan


Not so recently, when I worked on what were then called minicomputers,
the boot process went like this:

Set the front panel data switches to the bits of the first loader
instruction (in machine language, of course)
Set the front panel address switches to the first location of the
loader
Enter the data into memory by pressing the Store button.

Set the data switches to the second instruction and the address
switches to the second address. Press Store.

Repeat a dozen or two times to get the entire bootstrap loader into
memory

Load the main loader paper tape into the paper tape reader

Set the address switches to the starting location of the boot strap
loader

Press the Go button

When to main loader is in, load the paper tape of the program you want
to run into the reader

Set the starting address to the main loader's first address

Press Go

That loader will load the final paper tape automatically, thank Silicon

Over time the process was streamlined a bit, for example by letting the
storage address autoincrement after each Store operation.

Maybe you can guess how happy I was when BIOSes started to appear :-)


lol I'm sure you were! The first computer I used had the boot record on a
single tab card. It used up about 75 of the 80 columns. We whipersnappers
memorized the sequence and could type it in on the console
teletypewriter. It was faster than tracking down the boot card sometimes.