99
votes
Accepted
How much better was DEC Alpha than contemporaneous x86?
The Alpha team set out to create a high-performance architecture, planned to last for 25 years and allow for 1000-fold performance increase over those 25 years. So they placed some long bets, starting ...
- 123k
79
votes
Accepted
Why did 1950s-60s computers have such wide words?
And if you go back further, e.g. to the ENIAC, you'll see a word size of 40 bits.
And if you go back even further, to mechanical calculators, you'll see word sizes determined by the number of decimal ...
- 27.3k
72
votes
How much better was DEC Alpha than contemporaneous x86?
Stephen Kitt has done what seems to me an excellent job of outlining features and when they were introduced. I'll take a slightly different tack, instead picking a single point in time, and pointing ...
- 4,842
66
votes
Accepted
How should we interpret Dave Cutler's criticism of Unix?
The I/O model on "Cutler systems" – RSX-11M, VAX/VMS, Windows NT – is an asynchronous packet-driven I/O model, rather than the fundamentally synchronous I/O model of Unix. At its core, you ...
- 35.6k
47
votes
Accepted
Does the video game Control (2019) depict a real computer system? What is it?
TL;DR:
Is this a real system? Which one?
No, it's most likely not a specific machine but a setup to look contemporary.
In Detail:
I've come across several computers. (They all look extremely ...
- 223k
38
votes
Why did DEC develop Alpha instead of continuing with MIPS?
The main thrust of the marketing behind the DEC Alpha was its 64-bit microprocessor architecture. They got there years before potential competitors, including MIPS. At the time DEC was shipping the 64-...
- 60.8k
27
votes
Why did DEC develop Alpha instead of continuing with MIPS?
and would have improved the chances of a single RISC architecture
having wide enough industry support to achieve critical mass rather
than being outcompeted by x86.
It's important to remember that in ...
- 2,264
26
votes
Accepted
Did the PDP-8 designers consider a stack?
Without detailed documentation on the PDP-8 design process, we cannot say for sure. I suspect that while they may have briefly considered it, it was never a serious prospect.
The PDP-8 is just the ...
- 13.7k
25
votes
How widely was 0xDEADBEEF used as a placeholder, invalid value?
It can be found in implementations of zfs such as OpenZFS, inherited from the Solaris Kernel Memory C header file:
https://github.com/openzfs/openzfs/blob/master/usr/src/uts/common/sys/kmem_impl.h ...
- 938
23
votes
How should we interpret Dave Cutler's criticism of Unix?
While I am sure that the merits of Cutler's stated "low opinion" could
be debated, I'm interested to better understand exactly what he was
referring to here. There's no citation, and I haven't ...
- 12.3k
23
votes
How should we interpret Dave Cutler's criticism of Unix?
At the operating system level – as seen by applications – files in VMS are very record oriented. Guide to OpenVMS File Applications (336 page, 2MB PDF) probably goes into far more detail than anyone ...
- 1,081
23
votes
Accepted
What was this mini-computer tape troubleshooting process
While I can't be certain, what you describe sounds like some variation on what's mentioned in the description of Techmoan's The Magnetic Tape Viewer - see the sound on a tape:
Q) You can buy these ...
- 6,765
21
votes
Why did 1950s-60s computers have such wide words?
Longer words mean more bits can be processed at once. An 8 bit processor can perform a 32 bit calculation, but it has to do it in 4 stages of 8 bits each. A 32 bit processor can do it in one stage.
...
- 15.2k
21
votes
Accepted
Advantage of RS-232 over 20mA current loop
TL;DR:
It's a classic case of technological advancement vs. installed base
In the early days of electricity-based communication (i.e., telegraph and later TTY) there was no way to detect a voltage and,...
- 223k
19
votes
Does the video game Control (2019) depict a real computer system? What is it?
As @Raffzahn answers, this is probably a concocted image made to look like various real DEC setups. The attached image is of a PDP-12. You can see the heavy tilt towards DECtapes. You also see an ...
- 6,128
18
votes
Accepted
Were there any LSI-11 like home computers outside of Russia?
The Heathkit H11 was available either as a kit or pre-assembled. It never became really popular in the West, but it was one of the most powerful PCs available in 1978. It used the LSI-11 small format ...
- 9,336
18
votes
Accepted
DEC Alpha: why no 8/16-bit load/stores?
Support for byte writes throughout a memory system is expensive. Among other things, if one wishes to use error-corrected memory that can correct single-bit errors, a memory that can be written in ...
- 36.2k
18
votes
Why did DEC develop Alpha instead of continuing with MIPS?
DEC's use of MIPS was only ever as basically a stop-gap.
Before they used MIPS, DEC had started work on a project called Prism. It was intended to be their first commercial RISC processor. In June of ...
- 4,842
16
votes
How widely was 0xDEADBEEF used as a placeholder, invalid value?
In a similar vein, Algol-68R on ICL 1900 (a 24-bit machine) initialized memory to -6815700, which when displayed as text (four 6-bit characters), spelled 'F00L', as well as possessing numerous other ...
- 35.6k
16
votes
Accepted
Conditional skip instructions of the PDP-8
If you compare the octal opcodes for the skip instructions,
a bcd
| |||
7500 SMA = 111 101 000 000
7440 SZA = 111 100 100 000
7420 SNL = 111 100 010 000
...
- 27.3k
16
votes
Accepted
How did 36-bit computers format ARPANET packets?
However, at that time, the world had not yet settled on octets.
I beg to differ. If you look through brochures and manuals of next to all manufacturers, they tried hard to be IBM compatible at least ...
- 223k
16
votes
DEC Alpha: why no 8/16-bit load/stores?
Apart from anything else, Alpha was the VAX replacement - indeed, it was internally called EVAX. It would be necessary to take VMS source code written in VAX MACRO-32 assembler and compile it into ...
- 35.6k
16
votes
Accepted
IBM vs DEC and business partners
I don't agree with the answer you read on quora. DEC did have a partner relationship with a certain kind of customer, namely engineering and science labs. Ken Olsen and the engineering staff at DEC ...
- 6,128
16
votes
Advantage of RS-232 over 20mA current loop
The current loop goes all the way back to classic telegraphy. If there's current flowing, then that's one state. If there's no current, then that's another state. It's as simple as it can be. You ...
- 13.7k
16
votes
Accepted
What did Richard Stallman have against VMS?
I have access to the file RMS; VMS 7 dated 1980-07-12. I can't make it public, but I can read it and I believe it's ok for me to paraphrase and summarize it.
RMS argues VMS lacks several important ...
- 3,111
15
votes
How much better was DEC Alpha than contemporaneous x86?
I was at HP when the Alpha cancellation decision was made. In fact I was part of a team that ran comparative HPC benchmarks on Alpha and x86. The fact was that by 1999 the x86 Pentium-II was ...
- 151
14
votes
How much better was DEC Alpha than contemporaneous x86?
Alpha fizzled in the face of the HP/Intel partnership pushing their
Itanium 64-bit architecture
I think it's important to note that during this period, there was a widespread belief that the VLIW ...
- 20k
14
votes
Accepted
Why did DEC develop Alpha instead of continuing with MIPS?
DEC needed a 64-bit successor for their VAX. However, VAX was a very CISC architecture at a time when ISA and microarchitecture hadn't been decoupled yet. Turns out DEC had a very hard time trying to ...
14
votes
Accepted
Performance characteristics of the DEC Type 30 graphical display
This might just be stating the obvious, but Type 30 manual linked in the question describes the device as a random-position point-plotting cathode ray tube. Nowhere does the manual suggest it's a ...
- 35.6k
13
votes
How did 36-bit computers format ARPANET packets?
ARPANET isn't the only context in which the world of PDP-10 computing ran into data paths that used octets for framing. Four other contexts come to mind: 9 track magnetic tape, PDP-11 file exchanges,...
- 6,128
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