32MB lobotomy trial on thinkpad 600E update:

[thinkpadcollection]

No, that not a mint condition, came to me as worst condition; pink back light on startup, damaged HDD PATA socket from a ebay seller. So that thing was tried to fix PATA unsuccessfully then motherboard got 32MB memory lobotomy.

My advice, do not. This thing turns on with constant fan spin and no LCD even with both memory sockets filled. Unless someone modified the BIOS to rearrange memory banks to sockets only.

Cheers, thinkpadcollection.

[Neil]

I understand that you have nothing to loose here, so I guess this was just an experiment to see what would happen. On the other hand, what, if anything, were you hoping to gain?

[thinkpadcollection]

If this works, would have less power usage using one stick of 4 chip 128MB and pentium mmx on a 600 or overclocked 600E by swapped SDRAM for faster chips.

Pentium mmx modules uses TX chipset northbridge which is 128MB cachable range, otherwise we would be all one happy brunch fitting 512MB on pentium mmx with HX chipset modules. Hehe.

600X is still few and expensive on ebay and I would like to aquire one some day, even a base only and transfer LCD assembly to this. Cannot use 600/600E bottom case since 600X motherboard fits different way.

Cheers, thinkpadcollection

[danikayser84]

On a side note, I wonder if anyone has successfully replaced the on-board 32MB with 64MB on a 600E, or the 64MB with 128MB on a 600X? (imagine, a 600X with an 850MHz processor and maximum 640MB RAM...)

[rkawakami]

How did you attempt the memory lobotomy? Removal (desoldering) of the entire memory chip(s)? Or cutting traces and wiring pins? If it were me, I'd opt for the second method. Cut/lift the RAS pin from the motherboard and directly tie them to VDD (power). The chips would still draw some very low standby current, in the order of microamps, but they could never be selected for use and thus not draw any operational (active) power. There would be a question of whether or not the chip would power up correctly (DRAMs typically require several RAS wake-up cycles before they become functional) but this normally has to do with resetting some internal latches and/or providing enough time for some voltage pumps to activate. It would be very rare that the part would turn on and start consuming an enormous amount of current.

Along with this change you would also need to edit the BIOS to tell it to ignore the on-board memory. This has been discussed here before and I've set up a web site some time ago that describes the process:

http://www.kawakami-ca.com/ibm_600x/disable_memory/

[thinkpadcollection]

I have removed all the 4 chips, everything intact, with chipquik solder alloy removal kit and soldering iron only. This solder alloy works instantly and lowers the solder temp; then whole IC comes off with either soldering iron alone or with heat gun if fails to so. I kept this chipquik kit from my former TV repair work.

Good question on changing from soldered down 32mb to 4chip 64MB or 4 chip 128MB which does work in 600 as memory module.
*update*: 4 chip 128MB chips has pin 36 (A12) enabled while 4 chips by 32MB and 4 chips by 64MB is N/C. Even thinkpad 600E motherboard does not have this solder pad wired for A12.

How is this address (A0-A11 on mainboard, A0-12 for memory slots) wirings done? Is they are all wired together in parallel while all the other enable wirings addressed for each bank "aka group of memory ICs per bank"?

I wanted to see if could solder down 4 chips by 128MB onto motherboard and patch wires from A12 address of memory slot to all of these four chips via A12 onboard. That is where I need to know where to get A12 address from?

BTW: All these mentioned SDRAM ICs are all TSOP 54 pin packages and I did check all the datasheets for 4 chip memory modules of 32MB, 64MB and 128MB respectively and they are all same pinouts except (N/C or A12). 256MB not possible due to need to wire 8 chips per bank.

Thanks and cheers, thinkpadcollection

[thinkpadcollection]

Today, I took 4 chips 128mb simm for chips (16Mx16 format) and put them on 600E motherboard alone; no flying wires. No boot. Wired all the pin 36 (A12) on all 4 chips and placed other end of this wire to socket pin 70 address 12 aka A12. Boots with 32MB reported and works. Put in both 256MB sticks disables the onboard ram.

Moved end of this wire to (pin 112, A11) on the SODIMM socket. Boots up as before, same thing: boots up with 32mb alone, next add both simms in, boots up with memory onboard disabled. One stick in any socket, the 256MB + 32MB is displayed.

Funny thing the pin 70/A12 is present on this 600E memory slots means this could do 1GB if it is inclined to work. The datasheet for my micron 256MB modules says A12 is not connected, while 512MB modules does have A12 on pin 70.

Puzzled. The datasheet for original 32MB x 4 chips (16bits each) is same as all the other chips up to 256Mbit x 16 (aka 128MB 4 chips except for A12 is present). Also, All of them from 32MB to 128MB chips are 4 banks internally.

Cheers, thinkpadcollection

[automobus]

Did you remember to remove the SPD ROM (serial presence detect) when you removed the memory components? If you did not remove it, then failure to POST is expected.

IIUIC, if I correctly understand relevant technologies and concepts: Original SPD chip describes 32 Mio in integrated on-board slot, so if you replaced original RAMs with higher-capacity RAMs, but did not replace SPD, then system still detects just 32 Mio.



edit add: I did not know, 600's SPD data is stored in a more-central location. I have no experience with 600. I believe X22 has a SPD ROM in vicinity of SDRAM components, so I assumed also 600 uses dedicated ROM.

[thinkpadcollection]

Appears that "SPD" data for 32MB is embedded in BIOS. I would love to have help learn to decode and find that?

Cheers, thinkpadcollection