On Thu, 21 Apr 2022, Mike Katz via cctalk wrote:
Intel has never understood interrupts or good cpu architecture.
Look at the segment:offset architecture of the 8086 and of course it's single
interrupt (without the separate interrupt controller chip) vs the 68000
somewhat orthogonal 32 bit architecture and 256 interrupts with 8 levels
built into the chip.
I could spend pages just describing how the 68K chip just blows away the 8086
considering they were both released at about the same time.
For crying out loud the 6809 even though it only addresses 64K is a more
powerful processor than the 8086. Even with the 8086 clocking faster than
the 6809.
The over-simplification that I gave my beginning students:
Intel's chip design technique was to add features to the currect chip to
make the next one. So, starting with the 8008?, they added kludges to
kludges. Some of which made some things very awkward, such as the
segment:offset method to add more memory to a 64K architecture. BUT,
whenever they releaased a new chip, the software from the previous chip
needed only trivial modifications to work.
MS-DOS was based on CP/M (although NOT "plagiarized").
When the 5150(PC) shipped, major third part software packages became
available right away.
For example, when the 5150 (PC) came out in August 1981, Micropro
immediately got Wordstar working on it. 'course it took them much longer
to modify the documentation; we kidded them that that could have been done
faster with certain word processors.
IBM had Visicalc and Easy-writer; Wordstar (MicroPro) and Supercalc
(Sorcim) were announced and demonstated immediately.
On the other hand, Motorola did not modify their chips for the next major
one. Instead, they redesigned from scratch. It took a little longer, and
all software had to be rewritten, but they consistently ended up with THE
BEST chip ("ichiban").
The 6809 was THE BEST 8 bit processor. But, marketing??
They handed it to Radio Shack who decided it would be a cartridge based
home games machine, with chiclet keyboard, RF [ONLY] video, and minimal
expansion capability. Users hacked around those limitations.
When Apple made the Lisa, they had to write ALL software from scratch.
Other than some algorithms from the source code, none of their 6502
software could be simply "ported" to the 68000.
I have heard an anecdeote [from an Apple senior programmer] that during
development of the Mac, it was mandated that it would ship with FOUR major
software packages; but, with slipping deadlines, the four consisted of
Mac-Write, Mac-Paint, Mac-Write, and Mac-Paint. Apocriphal? but amusing.
When the Mac shipped, there was a frustratingly long delay for third party
software.
--
Grumpy Ol' Fred [email protected]
