Re: [amsat-bb] Still can't get InstantTrack to work without a co-processor

["Dennis Dease" <amsat@xxxxxxxxxx>]

Jeffrey S Austin wrote:


>Roy-
>No, if you look at any x86 chip you'll see either a SXor DX. All SX
>chips are without the math co-processor but generally have a socket on
>the motherboard for that chip.


This is not entirely correct. The x86 chips prior to the 80486 did not offer
integrated math processors.  The SX/DX designation used with the 80386
indicated the internal data path structure in the chip. It did not indicate
anything regarding a math co-processor.

   80286  16-bit word size, 16-bit data path
   80386SX 32-bit word size, 16-bit data path
   80386DX 32-bit word size, 32-bit data path

Prior to the 80486, math coprocessors were always an additional
chip with their own number.  Generally, that number corresponds to the
CPU number, different by one digit.

   8088 CPU              8087 coprocessor
   80286 CPU            80287 coprocessor
   80386SX CPU       80387SX coprocessor
   80386DX CPU       80387DX coprocessor

The 80486 came with a built-in math coprocessor that was either
enabled in the DX or disabled in the SX.  The math-coprocessor
add-on for a 80486SX was actually a complete 80486DX chip
that was mounted in the math co-processor slot.

So..

SX/DX means different things in a 486 than in earlier chips...

Best regards,

Dennis - N4NR






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