[Skimmertalk] red pitaya, for real?

[Jeff AC0C]

Let me help make it clear on the CPU scale.  You are over estimating the CW 
and under estimating the RTTY demand.

There is at least a 4x demand on RTTY skimmer compared to CW skimmer (server 
products) even on "normal days."  If there is a RTTY contest on, the demand 
jumps to 10x to skim one band (200+ decoders).  If you try to do multiple 
bands, then it's closer to 20-30x depending on frequency range and how much 
throttling you are willing to live with.  The previous gen i7-49xx (forget 
the model number) cannot skim 3 bands at 96 Khz without throttling in a 
contest.

Watching RTTY skimmer crush an otherwise speedy computer is something you 
really have to see to appreciate.

73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie

-----Original Message----- 
From: kazeringue--- via Skimmertalk
Sent: Thursday, September 01, 2016 12:14 PM
To: skimmertalk at contesting.com
Subject: Re: [Skimmertalk] red pitaya, for real?

Good information.

Makes sense, AMD seems to like to push the floating point stuff to the
gpu, graphics normally being the usual high volume fpu user in most
situations.  Certainly for their target budget gaming market.  Probably
helps them cut costs on the CPU's.  Seems like I read they are going
back to 1:1 with the next[?current?] line.

Not looking for a rtty skimmer anytime soon, especially if I need a late
generation i7 to run it.  Just looking for an affordable softrock
alternative for CW skimming the contest bands during the season.

So the general consensus is:
RTTY skimmer, more cpu horsepower, i7 best bet.
CW skimmer, more horsepower best, but possible to get by with less if
willing to live with load(or other compromise).

73 de w4kaz




> Do NOT use an AMD uP if RTTY skimmer duty is what you want.  This program 
> is
> a monster consumer of FPU calculation capability and while the AMD parts 
> are
> very fast, they suffer from a shared FPU core.  Meaning your zippy new AMD
> 8-core speed deamon actually has only 4 FPU cores, and they are shared one
> FPU to two CPU.  My rather ancient and slow (by modern standards) 945 runs
> around 300 decoders under RTTY skimmer despite being "only" a 4-core part.
> That's about the same speed as you get out of the later AMD parts.  Why?
> Because the 945 has a single FPU for each CPU.
>
> The Intel parts by comparison are faster because there is a 1:1
> correspondence between physical CPU and physical FPU cores.

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