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[linrad] CPU-load and delay on 486; Re: [linrad] Solution for Leif's Debian install on low memory computers

Hello all!

Before taking my couple of old 486's out of the dust, wouldn't
it be good to have a couple of reference values for the CPU-load
and signal delay under 'Linrad'. Possibly not much RAM-hardware
is needed for the actual running operation. Even if the delay would
be a couple of seconds, it would make 'Linrad' a perfect monitoring
tool around the 50/70/144 MHz calling frequencies, especially in
industrial or city environments with a lot of man-made noise.

As far as I have understood there are a few issues related to
CPU-load and delay. The reason that my Duron_1000 is taking so
much (15%) CPU load is probably mainly due to my high output
rate (48000). Adequate performance would be achieved already
with 6000 Hz sampling in the D/A converter, which would reduce
FFT-calculations substantially. I will see if the VIA VT82C686B
chip allows for independent sampling rates. It would be handy to
be able to do the complete 'Linrad' processing with a basic plain
motherboard (built-in audio and built-in graphics). Zero PCI/AGP!

Another thing is that 'Linrad' development has not been linear
through the years, meaning that Leif has reported several times
that the code has been substantially improved. Therefore it may
be that some listed values are not valid anymore for the newest
lir01-xx series (Leif, if that is what you mean by "too much"
information, then I could possibly agree, but there is a risk
to lose other embedded information if these old reports would
be removed; I guess the best is to display clearly the time
frame and technology/software versions during measurement).

Finally the (not so hypothetical) question is. Given a 486/33,
what is the approximate CPU load and delay with input sampling
at 48000 and output at 6000? My experience was that the screen
update was very sluggish initially in the lir00-xx series. So
possibly the main improvement has been there. Also ISA-cards
seem to slow down the CPU during transfers (a DMA issue)? For
passive monitoring I would allow several seconds of delay, but
for regular QSO's one second is about maximum, dependent on the
mode. Recent Skype-experiments (with occasional delays) prove
that the longer delays are very problematic in live discussions.

Hopefully we are able to progress from the software problems to
a real operating environment, even if it would be part-time....

             73, "Zaba"  OH1ZAA/2   [The sky is no limit]

P.S. I failed with an install on a Cyrix/166+ (forgotten CPU?).

At 19:06 24.4.2005 +0200, EA1ABZ wrote:

Hi Leif and Linraders.

I have googled a lot and getting pieces from many places, and found a solution mixing everything.
The trick is to create a swap partition to increase memory.

Sarge installer could not load the fdisk-udeb and more installer modules, because of lack of memory space, the trick is using first the WOODY installer (3.0r4 that works for Leif for example) for creating swap partition.

Boot with the woody installer and make a swap partition on your disk (50MB will do). If you have a swap partition on your disk there is no need to do it. Be sure that you create the swap before exiting.

Abort the woody installer and boot with the sarge installer.

Choose "expert26"

"entering low memory mode" ---> Continue
"choose language" + Enter  (only english will work on low memory mode)
"choose country or region" + Enter
"select keyboard layout" + Enter
"American english" + Enter
"select and mount cdrom" +Enter
"modules to load" -----> Continue
"prompt for parameters" ----->  NO
"start PC card services" ----->  NO
Continue  (it will detect the CDROM)

"Load installer components from CD" + Enter


ALT-F2  (to switch alternate text console)


Ensure what device corresponds to your swap partition that you create with the woody installer. In my case, it was created in the slave disk of the first IDE cable(in the second partition/dev/hdb2). It corresponds to /dev/hdb2 in Linux speaking, but here is different. bus0 is first ide cable, bus1 is second ide cable, "target1" is second disc. "part2" is "partition 2" (hdb2)

Do not blame me if you loose data on your disk!!!  ;-)


mkswap /dev/ide/host0/bus0/target1/lun0/part2  (this creates the swap)
swapon /dev/ide/host0/bus0/target1/lun0/part2  (this turns on the swap)

type "free" to see that swap is working

type "exit" to stop the text console

ALT + F1   to go to the install screen

Select all needed installer componets (now that you have swap, there will not be space problems. Select nic-******** stuff, or everything if you wish)


Configure the network
Go to "detect hardware"

Partition your disks, but DO NOT CREATE SWAP!. You have a swap already running

Continue with the installer untill you finish

That is all.
I have tested it here until partitioning the disks. And it works

Hope it helps.


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