[sebhc] DISKETTES and stuff

[Dave Dunfield]

>> I'm not sure, but I seem to remember that the main difference between
>> the 8080 and the 8085 was that the 8085 only needed +5 volts.
>
>Actually, there are a considerable number of differences between the
>8080 and 8085. They aren't even close to being pin-for-pin compatible.
>About the only thing that is the same is they both have the same
>instruction set (though even there, the 8085 has several additional
>instructions).

FWIW/IIRC:

The 8080 required three power supplies (+5, -5, +12), and the 8085
needs only +5.

The 8080 required a complex clock driving several lines (most people
used Intel't 8224 "clock generator"), the 8085 needs only a single
block, and can accept a directly connected crystal.

The 8080's bus is also complex, requiring the 8228 "system controller"
to obtain usable signals. The 8085 uses a simpler multiplexed bus and
ALE, requiring only a few latches.

The 8085 added four additional hardware interrupt inputs with on-chip
decoding and masking - these are the .5 vectors.

The 8085 added a pair of single-bit general prurpose on-chip I/O
signals (SID and SOD).

The 8085 got rid of the SYNC and INTE signals which made it less fun
to use with hardware front panels.

>From a software point of view, there were almost identical. There were
only two new instructions which used previously undefined opcode values.
These were SIM and RIM - to set and read the interrupt masks, as well
the single I/O bit.


It's interesting to note that the undefined opcode executed by HASL8
is RIM (0x20) - this means that it will trash the accumulator on an
8085, and therefore may NOT work the same as on the 8080.

Regards,
Dave
-- 
dave04a (at)    Dave Dunfield
dunfield (dot)  Firmware development services & tools: www.dunfield.com
com             Vintage computing equipment collector.
                http://www.parse.com/~ddunfield/museum/index.html

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