[waug] Re: Obstacles to Browser and system performance
- From: Mr N Rolfe <moss@xxxxxxxxxxxxxxxxxxx>
- To: waug@xxxxxxxxxxxxx
- Date: Mon, 17 Dec 2007 22:20:33 GMT
In message <BAY131-W17362EB8AAA428513363DAC0620@xxxxxxx>
incerti auctoris <incertia@xxxxxxxxxxx> wrote:
> In reference to questioning between Robin (me), Ian, Moss, and Derek at
> the last meeting:
> (Please correct any mistakes/misquotes I may have made!)
> TECHNICAL OPINION
> The above covers my opening question. Below are Ian's and Moss's initial
> replies before we ran out of time:
> Issues raised were:
> * Image Translation
> * Memory Paging
> * Bus Feed
> * No Native FPU
I will answer two of these tonight the others later , But #1 also
touches on #2 and #4
> IMAGE TRANSLATION (Moss)
> I don't understand what this is: Does it concern decoding of
> GIF/JPEG/PNGs, general shifting around of large blocks of data (perhaps
> related to Bus Feed), or some other hardware or OS limitation?
It is mainly to do with the decompression routines involving an awful
lot of processor grunt and maths , To turn the image into a format
suitable for the machine to display .
> NO NATIVE FPU (Moss)
> I thought there was an FPU (Floating Point Unit) available as a
> co-processor?
In regards Acorn/Risc OS I think only on the A5000
> What do you mean by "native"?
On Intel and AMD processors it is an integral part of the processor
not an add on.
> Is the existing FPU not built into ARM7/9/etc?
I think there was one in the Arm 7500 as used in the A7000 (+) ,
As for the Arm 9 pass .
> Does it not execute code fast enough to keep up?
It would be clocked at the same speed as the processor.
> Is it not a RISC/ARM processor?
No.
> What is the performance problem caused by not having it (whatever
> it is)?
The main performance hold up is that the machine has to use a
'Floating point emulator' which is a software program rather than a
hardware device . So you run in to the problem of having to move quite
large amounts of data between hardware and software . The main use of
the FPU is in maths , As if you want to do any thing more complex than
doing simple math functions on simple integers , Than you need a
floating point unit or emulator .(It is often refered to as a maths
co-processor)
> ARM VERSIONS
> This is a separate-but-related point that I didn't get around to
> raising:
> Are there any barriers to running RO on an ARM9, as opposed to on the
> ARM7 (A9) or IOP/XScale (Iyonix)?
My A9 Home runs an Arm 9 ! The Arm 7 was used in the Risc PC
> This was raised upon asking R-Comp at Guildford, why smartphones use the
> ARM9 series, while our desktop machines seem to be stuck at the ARM7
> level. (!?)
See above ^
Hope this clears up a few things Robin .
Moss (grows flat on a rolling stone) :)
--
Mr N Rolfe moss@xxxxxxxxxxxxxx http://www.mosschopps.org
4 x RiscPCs 1 x A9 1 x Risc cube ultra running VRPC Adjust
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