Questions tagged [microprocessor]
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7
questions
92
votes
6answers
9k views
Were there 8086 coprocessors other than the 8087?
The 8087 math coprocessor for the 8086 (and descendants) nominally added floating point and transcendental (trigonometric and logarithmic) instructions to the 8086. Contrary to naive expectations, the ...
43
votes
5answers
16k views
Why did CPU designers in the 70s prioritize reducing pin count?
A lot of 70s era microprocessors were packaged in DIP packages with 40 pins. This was a reasonably good fit for 8-bit processors: 16 address lines, 8 data lines, 2 power and clock are all absolutely ...
6
votes
2answers
1k views
How does Game Boy / Sharp LR35902 HRAM work?
The Nintendo Game Boy has RAM called "HRAM" (meaning "high ram")
decoded at locations $ff80 through $fffe. (All other decoded
locations in the $ffxx page appear to be I/O device and system
control ...
29
votes
5answers
6k views
How was microcode implemented in retro processors?
How was microcode implemented in retro processors such as the Z80 or 8080?
Was the microcode standard (for example a manual for the processor outlining all possible micro-instructions and the ...
34
votes
2answers
2k views
Can the two CPUs in a Commodore 128 run at the same time?
The Commodore 128 has two CPUs. One is some variant of the 6502, and the other is a Z80.
One CPU is there for compatibility with the Commodore 64 and the other is there presumably to give basic ...
19
votes
3answers
3k views
What happened to the 65832?
In his June 1985 foreword to Programming the 65816 by David Eyes and Ron Lichty, Bill Mensch expresses his hopes for a 6502-derived 32-bit microprocessor: the 65832. WDC is still thriving, but the ‘...
6
votes
1answer
353 views
Tannenbaum paper on constants in ISAs?
I see many references to a paper by Andrew Tanenbaum that demonstrated the vast majority of constants would fit into 13-bits, and I seem to recall it being in my university text on CPU design. However,...
