The official 755 Upgrade and general information Topic

[OhYou_]

After buying four of these 755CD I finally have a good working one in now great condition, but I have a couple of questions.

it seems the popular 32MB dram cards will only work in a pentium 75, but what about the 59G3998 memory expansion card?
I own one of those and could not find any ram that would fit it, so never tried it in at that time my sort of working p75.
My good one is a 486, and I want to keep it that way, but I also would like to have 40MB of ram again and I think that is the way.

The battery on the 486 models could only be nimh it seems, Has anyone seen the recent ish project someone took on to replicate a 701c battery with all new components, reverse engineering the original battery IC and replacing it with a microcontroller?
I know newer thinkpads are legos when it comes to batteries, like if it physically fits the connector it works, but I am not sure on these older ones if it is possible to replicate this, or if there is a clear difference between the 701c nicad battery management and the 755cd nimh battery management.
I have a corroded nimh I could crack apart but I would have to likely deadbug the chips since the legs are likely gone and I would rather just con it into thinking its fine and supplement my own lithium based bms and cells.

I also have a assortment of busted up 755CD that all dont work in various ways, does anyone have a board schematic for the motherboard in these? I feel like at least one more could be saved to also have a p75 in my collection, but they all have been absolutely shredded by the [censored] memory battery leakage. My working p75 died somehow after sitting for 7 years despite mitigating leakage damage and I have not looked into it much yet.

Is there something special about the hard drives for these? I have tried a few different drives in it and only the original one works, even a period correct seagate st9190ag is unrecognized. I'm fine with using original ibm hard drives and they are cheap as on ebay but I'm a bit interested in other options to try later on.

I can pop up a picture of the memory expansion card adapter if needed, just have to find it.

[solidpro]

Does anyone know how to amend a Wikipedia redirect search phrase and turn it into a basic article?

I'm doing a review of all the 755 machines I owned and usually how I would start is to print off a page - often Wikipedia, which would have a reasonably truthful and reasonably complete list of the various models in the range. However, I was suprised to find there is no article for the 755, despite there being a page for the 750 and the 760 - arguably less popular or widely known models.

I don't know enough about wikipedia to turn a redirect into a basic article that can then be added-to.

I have:
1 x 750c
1 x 755C
1 x 755Cs
2 x 755CD,
1 x 755CDV panel only,
1 x 755CE,
No 755CSE or 755CV
5 x 755CX
One massive dock and one small dock.

But I think I need to slim down....!

[dr_st]

You just edit the following page:
https://en.wikipedia.org/w/index.php?ti ... ction=edit
Remove the redirect tag and add content like on a normal page.

[solidpro]

Cool, I've added some basic info, I hope it stays up! I'm always thinking thinkpad pages are a little lacking - especially when it comes to any useful information in a nutshell about preservation, so I've added a bunch of stuff in and I hope it doesn't get removed.

[evening_hunger]

Isn't Pentium 75 another socket and different core voltage?

Not on the 755CE and above. Same exact socket.

Then, I think I'm gonna hit ebay to look for some P75.
Thing is, I'm getting kind of lost looking at the photos of these CPUs.
For example, comparing this this one with a properly chosen version of this one (from a dropdown list) we don't always see the same pinouts... (I don't know how this compares to the 486dx100 i have)

[solidpro]

AFAIK the CPU cards are interchangable because many of the 755 series offered either 486 or Pentium configurations and besides the CPU daughterboard, they're the same.

[goldeneagle]

They are the same systemboards. I've upgraded many 755CE's with upgraded CPUs. I actually just found a supposedly NIB Pentium 75 upgrade for a 755CE/CX (but I think it's the whole motherboard, not just the CPU module).

The P75 is definitely faster, because you have some cache that you didn't have with the DX4-100. It makes playing games like Duke Nukem 3D much more tolerable.

[Misu]

After buying four of these 755CD I finally have a good working one in now great condition, but I have a couple of questions.

it seems the popular 32MB dram cards will only work in a pentium 75, but what about the 59G3998 memory expansion card?

32MB dram cards work in 486 based 755 models. The only thing is that parity option in BIOS has to be turned off. I am a happy user of one 775C with 486 DX2 and 36MB RAM that is booting DOS from 256MB CF card in PCMCIA adapter
No FDD, no battery, no HDD, but 3 places for a good packed lunch in the lunch box

[solidpro]

Funny, I also just noticed this last weekend.

I noticed on the 755 machines, all 486 variants are Parity RAM and Pentium variants are non-parity. My memory of the 755 series though is that the CPUs sit on an interchangable daughterboard - and I've known people to upgrade from a 486 to a Pentium via switching the CPU board between models from 486 to Pentium, and was wondering if that created some mismatch between the motherboard and the CPU board? I don't know enough about the correllation between Parity/NP RAM and 486/Pentium. Interesting you say there is a option to turn parity off in the BIOS though - I'd never spotted this.

You're saying also a 755 will boot from a PCMCIA adaptor with CF card? That's also news to me.

Finally worth noting that using the 755's SO-DIMM adaptor, you can go to 40Mb on some models.

[Misu]

It is exactly 755C - 9545-TFT. I use generic SanDisk "nobrain" 16bit adapter.

The card is SMART CF Card XL 256MB - https://www.mouser.com/ds/2/723/CF_Card ... 607266.pdf - if I remember right, it is a non-DMA card.

It was partitioned, and the system was installed in Dual CF to IDE adapter (from Delock) in some other ThinkPad - everything was done with PC DOS 5.02 install floppies. No other special tools.
I have also that small plastic cover covering PCMCIA slots, so it looks like nothing is there