5 expanded posts ยท every known parent and child
Lady Ada writes: >The ideal phone might be based on CPU's, RAM, and DSP's, with no >DES chips or anything like that. Have you seen the prices of used original NeXT equipment lately, or just the prices of single system boards from back in the 68030 era? Anyway, why do you need a DSP? I have read in several places that DSP's are going to be "replaced" by the CPU as time goes on and the CPUs just get more and more powerful. Phil
>
>
> Lady Ada writes:
>
> >The ideal phone might be based on CPU's, RAM, and DSP's, with no
> >DES chips or anything like that.
>
> Have you seen the prices of used original NeXT equipment lately,
> or just the prices of single system boards from back in the 68030
> era?
>
> Anyway, why do you need a DSP? I have read in several places that
> DSP's are going to be "replaced" by the CPU as time goes on and the
> CPUs just get more and more powerful.
>
> Phil
This seems like a strange comment since DSP's are general purpose
processors that are optimized for a certain range of price/performance.
Actually, I've been seeing hints that most systems will start
augmenting the main processor with DSP's to solve the realtime /
multiprocessing problem.
Zyxel modems have 2 DSP's + a 68000.
I've been reading up on them recently...
sdw
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where it is convenient to post from or thru.> >The ideal phone might be based on CPU's, RAM, and DSP's, with no > >DES chips or anything like that. Probaly CPU is not necessary... > Have you seen the prices of used original NeXT equipment lately, > or just the prices of single system boards from back in the 68030 > era? No. Care to enlighten? > Anyway, why do you need a DSP? I have read in several places that > DSP's are going to be "replaced" by the CPU as time goes on and the > CPUs just get more and more powerful. Since, as somebody has already mentioned, DSP is a CPU optimized for price/performance in digital signal processing, the statement above sounds funny. DSP chips will always be cheaper than general purpose CPUs offering at least comparable performance. -- Regards, Uri uri@watson.ibm.com scifi!angmar!uri N2RIU ----------- <Disclamer>
> Anyway, why do you need a DSP? I have read in several places that > DSP's are going to be "replaced" by the CPU as time goes on and the > CPUs just get more and more powerful. Yeah, eventually. Analog Devices 2105's cost $12 in quantity 1. They are capable of doing 2 data moves, a 16x16 multiply, a 40 bit accumulate and a prefech of the next instruction all in 100ns. 10 Million Multiply-Accumulates per second. Ever tried that on a 386? For more money, you can get ones with 60ns clocks (16.7 MACS). Eric Blossom
>They are capable of doing 2 data moves, a 16x16 multiply, a 40 bit >accumulate and a prefech of the next instruction all in 100ns. This is where a DSP really shines, since it's the fundamental operation in digital filtering; indeed it wouldn't be a DSP if it couldn't do a multiply/accumulate in a single clock cycle. But I wouldn't be too surprised if general purpose CPUs eventually get the same capability. And once they are, the distinction between a "DSP" and a "general purpose" CPU will pretty much vanish. DSPs are notoriously harder to program than general purpose CPUs, and being lower volume items they won't be able to compete in price or clock speed with general purpose CPUs made in the millions. But that's in the future. There's not much alternative to using a DSP chip right now if you want high quality low bit rate speech, but unfortunately the low-cost DSPs now appearing on PC sound cards are not quite up to the task yet. I think CELP encoding requires something like 30 million multiplies per second, which is beyond the reach of a 12.5 Mhz AD2105. On the other hand, simpler schemes and/or clever coding tricks might make it possible. And since these boards are now widely available in computer stores, they're hard to ignore in a project like this. Has anybody looked at them in detail? Phil