Patrick
Although the amount of RAM may not be critical (provided you're not paging), the SPEED of the memory is probably the limiting factor. The summary is that in a modern cpu with multiple cores and pre-fetch pipeline processing, the processor can execute instructions faster than they can be retrieved from main memory. Access to the L1/L2/L3 caches is much faster than access to main memory, so designing a program so that as much of it and it's working memory will fit into the cache as possible can make a big difference to performance. What this means for the discussion is that when comparing PCs, don't look just at the cpu speed and amount of RAM; consider the speed of the RAM too. I'm getting ready to buy a new PC now and it having DDR3 memory is more impotent to me than the highest possible cpu speed. Sources - this presentation explains a lot about modern PC architecture and performance: http://www.infoq.com/presentations/click-crash-course-modern-hardware If you really want the nitty-gritty, take a look at this classic paper, which is LINUX oriented, but still applies to a Windows PC: "What every programmer should know about memory" http://people.redhat.com/drepper/cpumemory.pdf John - K6CKP --- In digitalradio@yahoogroups.com, "Patrick Lindecker" <f6...@...> wrote: > > Hello Tony, > > According to my tests, it is only the capacity to do calculations which is > the key, as a lot of digital processng is done (for example for SDR or > Panoramics). I don't think RAM is important. I mean either you have > sufficient memory or you have not (and you will have a message error). But > if you have enough, having double or four more that the minimum does not > change anything. > > Note: with or without BPSK31 panoramic, I have about 2 % of CPU usage. > > 73 > Patrick > > > ----- Original Message ----- > From: Tony > To: digitalradio@yahoogroups.com > Sent: Saturday, January 30, 2010 4:35 AM > Subject: Re: [digitalradio] SDR-Radio with DM780 20M Digital Band > > > > > > Patrick, > > Thanks for the information. As you may have read from my reply to Andy, my > CPU usage seems to be very low with Multipsk. It's well below 10%. > > Is there a particular Multipsk mode or configuration that would tax the > system? I'd like to try it and see how it affects CPU usage. > > Merci mon ami... > > Tony -K2MO > > ----- Original Message ----- > From: Patrick Lindecker > To: digitalradio@yahoogroups.com > Sent: Friday, January 29, 2010 4:51 PM > Subject: Re: [digitalradio] SDR-Radio with DM780 20M Digital Band > > > > > Hello Tony, > > I have here two PC XP at about 2.4 GHz (single core): > > I have compare these two XP computers on the same file to decode (in > 110A): > * the first one (the oldest) which is an AMD Atlon 2500+ 1.09 GHz 768 Ko > RAM takes 75 seconds to decode it, > * the second one which is an AMD Atlon 2400+ 2 GHz 736 Ko RAM takes 20 > seconds to decode it. > > On the most modern (about 3 years old) with SdR and RS ID detection on 44 > KHz, the CPU load is about 35 to 40 %, but on the old one it is 100 % (the > program does not work in fact). > > So normally with a modern PC it is OK. With an "old" PC, it can be > problematic. > > Note: with my Vista laptop (dual core), the CPU load is about 25 % in the > same conditions. > > 73 > Patrick > > > > ----- Original Message ----- > From: Tony > To: digitalradio@yahoogroups.com > Sent: Friday, January 29, 2010 8:36 PM > Subject: Re: [digitalradio] SDR-Radio with DM780 20M Digital Band > > > Andy, > > I plan on switching to SDR in the near future. My current PC is a dual > CPU 2.2GHz Dell with 3 GHz RAM. Any idea what the minimum PC requirement is > to run Multipsk with SDR? Could you also tell us what processor you're > running now? > > Thanks, > > Tony -K2MO > > ----- Original Message ----- > From: Andy obrien > To: digitalradio > Sent: Friday, January 29, 2010 9:11 AM > Subject: [digitalradio] SDR-Radio with DM780 20M Digital Band > > > > One of the things that I wanted to accomplish with an SDR receiver, > is the ability to keep an eye on the whole 14065 to 14115 frequency > range. If I was down on 14074 monitoring ALE 400 traffic, I would > miss Olivia signals that popped up in the 14109 area. I would also > miss Hell signals at 14068. Now the SDR affords the opportunity to > keep an eye all all at once. My venture in to SDR from a digital mode > perspective has led to a discovery that, other than Multipsk, the > current state of the art does not support direct monitoring of wider > I/Q data. I'm also challenged in that my PC cannot cope with the > Multipsk CPU demand when I try direct monitoring. So, at the moment I > am visually monitoring signals with the SDR and using traditional > software methods to decode the 3-4 kHz of audio that is fed from the > SDR to applications like DM780 or Fldigi. > > At this screen shot http://www.obriensweb.com/sdrdm780.jpg > > you will see how it appears. I am simply using DM780 and SDR-Radio > software together. When I need to transmit, I just use my TS2000 > after dialing in the signal discovered by the SDR receiver. Simon > HB9DRV will likely "integrate" these two applications later in 2010. > > I did catch a Russian on RTTY this morning that I would have otherwise > missed while I was slumming it in PSK31-land.. Multisk does RS-ID > over this entire 14065-14115 portion, and DM780 is likely going to > include this ability in the future. If people use RS-ID often enough, > it will be really "cool" to monitor 14065-14115 and get RS ID alerts. > > So, just over a week playing around with the SDR receiver... I see the > potential... digital mode applications are not quite "there" yet. > When they are "there" (as in Multipsk) my PC isn't. This $41.00 Ebay > PC may eventually get retired for a slightly improved one with better > CPU. OK, back to keeping an eye on 14065-14115. A-ha, an SV3 calling > CQ RTTY, 14082. > > Andy K3UK >
