Questions tagged [arm]
ARM is a British processor manufacturer that evolved from Acorn Computers in 1985.
18 questions
3
votes
1
answer
186
views
ARMv4/ARM7: Does writing to PC using LDR flush the pipeline?
This is a question about the ARMv4 architecture, particularly as embodied by the ARM7TDMI processor.
Does writing to R15 using LDR flush the pipeline? Naturally, it's clearly documented that BX ...
- 267
13
votes
2
answers
399
views
ARMv4: Does reading PC with a "shift by register" operand really offset it by an additional 4 bytes?
Section 4.5.5 of the ARMv4 docs read (my emphasis):
4.5.5 Using R15 as an operand
If R15 (the PC) is used as an operand in a data processing instruction the register is used directly.
The PC value ...
- 267
4
votes
0
answers
121
views
What are the legal values at offset 0x30 in the Risc OS AIF header
I'm now poking around in the binary executable file format of the Acorn Archimedes family of computers, Arm Image Format or AIF.
It doesn't have a magic word but the *nix file utility identifies them ...
- 7,874
14
votes
0
answers
735
views
Original instruction set for the first ARM processor
I'm studying ISAs and would really like to see the very first ISA that Sophie Wilson chose/put together when designing the very first ARM CPU while at Acorn Computers around 1983 or so.
From what I ...
- 351
9
votes
6
answers
963
views
Would compare-and-branch have added an extra cycle on ARM-1?
The ARM-1 was an early RISC CPU, designed in 1986 (and even more typical of early RISC design constraints than the year would suggest, since Acorn didn't have the budget to pay for the latest process ...
- 63.8k
7
votes
1
answer
810
views
Is there a list of the differences between the various ARM architectures?
I am in particular interested in the differences between ARMv4 and ARMv7 (I have a particular task in mind), but to make this question more generally useful to future readers, I'll ask more generally ...
- 39.7k
10
votes
1
answer
1k
views
What are the “building bricks” of ARM’s design that this magazine article is referring to?
I came across an early mention of the ARM in New Scientist of June 18, 1987:
https://books.google.ca/books?id=LvhAoKR-ixwC&pg=PA41
It has this statement:
They realised that many of the ...
- 21k
8
votes
3
answers
831
views
Did the ARM-1 really outperform the 387?
According to a comment on https://news.ycombinator.com/item?id=31985142
The first benchmarks indicated the plain Archimedes had higher FP throughput than a 16MHz 386 with a 387.
The original ...
- 63.8k
15
votes
5
answers
1k
views
Has there been any effort to research the undocumented Thumb instructions of ARM7TDMI?
Many CPUs have "holes" in the ISA, where the bit pattern is left undefined.
Considering the Z80 and the 6502, many people have mapped out what these undocumented instructions actually do.
...
- 39.7k
-6
votes
1
answer
671
views
Is the Raspberry Pi Model B (2014) technically inferior to an original Xbox (2001) in compute power/specifically for emulators? [closed]
(I first asked this in the Raspberry Pi section, but it received no responses. I think this, Retrocomputing, might be a better fit.)
I the year 2003, I had my Xbox chipped in order to be able to run ...
- 1
10
votes
2
answers
912
views
How fast did the ARM-1 access memory?
The ARM-1, an early 32-bit RISC CPU, was used in the Acorn Archimedes computers, released in 1987. Its rated speed was one 32-bit instruction per cycle at 8 MHz.
Typical RAM chips at that time would ...
- 63.8k
24
votes
2
answers
1k
views
History of ARM Linux and FPA
ARM Linux, at least Debian was traditionally (pre eabi) built for the FPA floating point unit*. Unfortunately under old ABI it was not easily possible to mix soft-float code with FPA code. The result ...
- 3,344
8
votes
2
answers
4k
views
What sort of SBC is in the C64 Maxi?
Curious as to what model SBC this unit is using
https://retrogames.biz/thec64
8 bit guys teardown says the internals are 'an ARM computer similar to a Raspberry Pi'
https://youtu.be/kxx2F4ffmeE
- 1,258
10
votes
4
answers
1k
views
Why didn't the Acorn Archimedes support general purpose co-processors?
Acorn's BBC Micro series is well known for the range of add-on processors (or Second Processors) that could be connected through it's Tube interface. These included the 6502, Z80, 80186, and also the ...
- 8,366
18
votes
2
answers
2k
views
Did any early RISC OS precursor run on the BBC Micro?
Acorn famously developed the ARM microprocessor using their existing BBC Micros internally, both to simulate the ARM and to develop for actual ARM using a Tube-connected second processor.
Later, ...
- 61.5k
2
votes
2
answers
1k
views
Differences between normal ARM7TDMI and ARM7TDMI used in GBA [closed]
I was wondering if there are any significant differences between a plain old ARM7TDMI processor and the ARM7TDMI the GBA console uses.
I'm interested in learning to program a GBA or an ARM7 type ...
user11207
8
votes
5
answers
794
views
Why isn't the approach to lower power CPUs guided by design rather than accident?
We know that the ARM chip came out of the Acorn computing initiative.
In the book The One Device, we read:
The low-power big thing that the ARM is most valued for today, the reason that it's on ...
- 3,067
26
votes
2
answers
3k
views
Was the first ARM "processor" a BBC BASIC program?
The best background I have found so far on the early development of the ARM processor at Acorn comes from this interview with Steve Furber.
The interview does not mention the development of the first ...
- 61.5k