>>> I gather ARM is quite a popular architecture. I don't know whether
>>> that's because there's readily available chips and IP-cores, because
>>> it's low-power, or because it's really easy to program...
>>
>> Low power.
>
> Why is that? It is because there's something particular about this
> instruction set which makes it especially suitable for low power? Or is
> it merely that a lot of people have spent R&D on making low-power
> implementations of it?

The former I would guess, as even the first versions used in the Acorn 
desktop machines were very low power when they probably didn't have any 
budget, time or real incentive to reduce it. I'm sure since then though 
there has been huge pressure and R&D expenditure to reduce it further.

This list is quite interesting:

https://en.wikipedia.org/wiki/Transistor_count

At each point in time the ARM CPU seems to have about 10x fewer 
transistors than its x86 equivalent. As a very rough I guess I'd say 
that means it used 10x less power. In thermal terms that is probably 
enough to make the difference between needing a heatsink and fan and 
working with just the bare chip.

What's also interesting is that the ARM2 had 25k transistors, yet 
further down the page it claims 21k transistors are needed for a 32-bit 
multiplier. Figure that one out. I think the answer is that on the ARM2 
the MUL instruction was the only one (apart from the load/store multiple 
register instruction) that took more than one clock cycle. As such it 
probably used a much smaller circuit to do it in chunks.

It also interesting to note that even on the earliest cores you could do 
an arbitrary bit-shift for free with every instruction on one of the 
source registers. So if you wanted to multiply by 320 (commonly needed 
in graphics algorithms of the day) you could do it with a single move 
and add instruction:

result = y << 8
result = result + y << 6

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On Mon, 02 Nov 2015 13:01:37 +0000, Orchid Win7 v1 wrote:

> But hey, Intel invented the Itanium to get away from all that... and
> nobody bought it.

Heh, yeah, it turns out that people want to be able to use the software 
they've purchased.

Jim



-- 
"I learned long ago, never to wrestle with a pig. You get dirty, and 
besides, the pig likes it." - George Bernard Shaw

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On 02/11/2015 05:16 PM, Jim Henderson wrote:
> On Mon, 02 Nov 2015 13:01:37 +0000, Orchid Win7 v1 wrote:
>
>> But hey, Intel invented the Itanium to get away from all that... and
>> nobody bought it.
>
> Heh, yeah, it turns out that people want to be able to use the software
> they've purchased.

But all you need to do is run the source code through the other compiler...

...oh, wait. Somebody in marketing just realised we can charge the 
customer money to buy the software again. *sigh*

Post a reply to this message

On Mon, 02 Nov 2015 18:09:37 +0000, Orchid Win7 v1 wrote:

> On 02/11/2015 05:16 PM, Jim Henderson wrote:
>> On Mon, 02 Nov 2015 13:01:37 +0000, Orchid Win7 v1 wrote:
>>
>>> But hey, Intel invented the Itanium to get away from all that... and
>>> nobody bought it.
>>
>> Heh, yeah, it turns out that people want to be able to use the software
>> they've purchased.
> 
> But all you need to do is run the source code through the other
> compiler...
> 
> ...oh, wait. Somebody in marketing just realised we can charge the
> customer money to buy the software again. *sigh*

Like most software companies do.

And most software that people purchase doesn't come with source code.

Jim



-- 
"I learned long ago, never to wrestle with a pig. You get dirty, and 
besides, the pig likes it." - George Bernard Shaw

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•On Tue, 27 Oct 2015 00:43:59 +0200, Orchid Win7 v1 <voi### [at] devnu
ll> wrote:

> On 26/10/2015 09:06 PM, Le_Forgeron wrote:
>> Only 2 colours per 8x8 pixels was the main drawback of the display.
>
> Oh yeah... I forgot about that! One time I wrote a program to draw  

> randomly positioned circles in random colours. After a few minutes of 
 

> drawing, most of the pixels were in the "on" state, but there were wei
rd  

> squares of colour that changed every time a new circle was started.
>
> I also remember saving several test patterns to tape, and eventually  

> discovering which colour provoked which tone from the speaker... Jesus
,  

> I was bored as a child!
>
> I've always wanted to know... why is the framebuffer arranged so  

> weirdly? Like, as you load a picture file, rather than filling from to
p  

> to bottom, it seems to fill every Nth line...

I remember

•Upgrading my 16K to a 48K
•Doing string-art type designs just to see the interesting desig
ns that  

aliasing resulted in.
•Designing my own fonts.
•Printing a school project on thermal paper. Bad idea.
•Making a 3d wireframe modeler that could only take 100 edges. T
he  

wireframe "render" could then further be coloured and textured with my  

custom paint program. Since I didn't have a joystick, I controlled the  

brush with 2 different systems: Angular (L & R arrows altered the angle 
of  

movement) an Normal.
•Dumping my Speccy in the bin because it died and you couldn't g
et parts  

anymore.

Now if I could just find the time to learn proper programming and contin
ue  

the 3d project on my pc.

-- 

-Nekar Xenos-

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