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I have checked this information by modifying another board to 32Meg. TomW

If you want this (with a 32Meg SODIMM installed as well):



blob version 2.0.5-pre3 for TuxScreen (Shannon)
Copyright (C) 1999 2000 2001 2002 Jan-Derk Bakker and Erik Mouw
blob comes with ABSOLUTELY NO WARRANTY; read the GNU GPL for details.
This is free software, and you are welcome to redistribute it
under certain conditions; read the GNU GPL for details.
Memory map:
  0x01000000 @ 0xc0000000 (16 MB)
  0x01000000 @ 0xc8000000 (16 MB)
  0x01000000 @ 0xd0000000 (16 MB)
  0x01000000 @ 0xd8000000 (16 MB)
Loading blob from flash . done
Loading kernel from flash .... done
Autoboot (3 seconds) in progress, press any key to stop .




# cat /proc/meminfo
        total:    used:    free:  shared: buffers:  cached:
Mem:  63918080  3715072 60203008        0     4096   888832
Swap:        0        0        0
MemTotal:        62420 kB
MemFree:         58792 kB
MemShared:           0 kB
Buffers:             4 kB
Cached:            868 kB
SwapCached:          0 kB
Active:            584 kB
Inactive:         1048 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:        62420 kB
LowFree:         58792 kB
SwapTotal:           0 kB
SwapFree:            0 kB


You have to change the CPU board RAMs to Micron MT4LC4M16R6-TG6 (or similar) and change mdcnfg in buildroot-tux/build/blob/src/blob/memsetup-sa1100.S to "mdcnfg: .long 0x0334b23f". Then you have to install a 32Meg SODIMM with 4k refresh. You must insist on the 4K refresh!

The photo was courtesy of GPSFan and his most excellent camera setup! Thanks again!

http://tuxscreen.net/img/Mods-Tux-32Meg.jpg

Desoldering RAMS.

I am sure that there are some people skilled with the use of an iron that are intimidated by the prospect of changing a surface mount device. Don't be, with some care, you can use a Weller 40W iron, rosin flux and solderwick to take the components off the board, then install the new ones.

Perhaps the safest way to remove the old DRAM chips is to use an X-acto knife. Position the side of the knife against the body of the part, using firm pressure, shear the pin "shoulder" from the plastic body of the old DRAM. Continue doing this, a couple of pins at a time, until all pins have been freed. Then, remove the plastic part, you will be left with two rows of just pins soldered to the board.

Flux the two rows of pins, then carefully "wipe" those pins off the surface mount pads. After you have removed the pins, "wipe" the pads clean of excess solder using solderwick. Do not use a lot of heat, if you do something wrong, stop, let it cool a bit, then try again. You will cause the SMT pads to become unglued it you use prolonged heat, the key is to use only as much heat as necessary and not to overheat the pads. It is important the the pads be clean of solder bumps for when you mount the new chips.

With all the old DRAMs removed, take one new chip and position it on the surface mount pads. Tack solder two opposite corners to fix it into position. Then, "flood" solder the remaining pins. What I mean by flood soldering is to solder the pins without too much regard for creating solder bridging, but don't use 1/4 pound of solder on each chip! Once the chips are soldered, use the end (not side) of solderwick to clean up the solder bridges. Carefull! If you pull too much solder out you will leave the pad "dry" and it may not be making a connection, but the pin may only be resting on the pad. (BTW, that is the other technique for removing ICs, wick out all the solder and pop them off the board. The danger is not having all the pins desoldered and end up tearing a pad off the board.).

Check your work with a child's microscope, if possible, or an eye loupe. Checking your work with an Ohmmeter for shorts is good practice (especially if the Tux wont' boot). Don't bother using the meter to check for how well you did in soldering the pads, a visual inspection is better. A 10X microscope, or eye loupe is fine for inspecting 0.050 center pads. Make sure that you see a nice fillet of solder on each pin. BTW. I do my rework with a 10X binocular microscope and a 40W Weller pencil with 0.020" solder. Tricky but you can do it, just file a slight bevel into a conical tip to "grip" the solder.

TomW



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