Re: Intel vs 6502

["Charlie" <charlied@NOSPAMbboard.com>]

"Kelli Halliburton" <kelli217@crosswinds.not> wrote in message
news:GN6Q9.308$Cp7.97@newssvr19.news.prodigy.com...
> Bryan Parkoff wrote:
> >     What I understand is that Intel has more instructions than 6502
> > does. For example, 6502 does not have floating registers, but it has
> > to build routines in order to support floating registers.  It can
> > decrease the performance.  Intel does have built-in floating
> > registers including more floating instructions that may improve
> >     performance.  Does it make sense? If we WANT to design
> > microprocessor from scratch that will add floating instructions to
> > 65816 and 65832, it is impossible to duplicate the 65816
> > microprocessor's schematic, but we can study using AND/OR/NOT GATES
> > and boole truth table inside microprocessor's schematic in order to
> >     create binary instructions. If we have to break black cover
> > before we can see naked IC wires inside microprocessor, it might
> > provide us more information before we can be able to build one from
> > scratch.  What do you think?
>
> Well, Roy has convinced me to give this group another chance. So here I go
> with my attempt to contribute positively. (Watch me wind up putting my foot
> in my mouth.)
>
> The original 8086, and its stablemate with the 8-bit data bus, the 8088, did
> not have floating point registers -- they were only implemented in the 8087.
> This was followed in turn by the 80287 and 80387 (was there an 80187 to go
> with the underappreciated 80186?)

No, there was no 80187 and the the 80287 was just an 8087 with different pins.

> until the floating point circuitry was
> integrated into the 80486. The 80487SX was simply a fully working 80486DX
> chip that replaced the functionality of the 80486SX chip, which was just an
> 80486DX that had a disabled floating point system.
>
> The 68000 series did not include an internal floating point system until the
> 68040. Motorola floating point accelerators included, if I recall correctly,
> the 68851, 68852, 68881, and 68882. I believe, but I'm not sure, that they
> were designed to be the companions respectively of the 68000, 68010, 68020,
> and 68030.
>
> While the various floating point chips were designed to work best with their
> companions, it is theoretically possible for any CPU to use any FPU, given
> the right software and interface logic.
>
> That is to say, for a dedicated individual, it would not be impossible to
> use a Motorola 68851 or an Intel 8087 with a WDC 65816, although a
> speed-matched FPU might be better suited, in order to use the same clock and
> not require async operation. I think neither the 8087 nor the 68851 were
> that widely sold in speeds greater than about 8MHz. Given that the 65816
> seems to run up to about 20MHz, perhaps a 68882 or 80387 would be a better
> match. But then, you have to deal with the 32-bit data bus of the 68882 and
> 80387. (Was there an 80387SX with a 16-bit data bus to go with the 80386SX?)

Yes, there is an 80387SX to go with the 80386SX.

Charlie