/insert GTA San Andreas 'there we go again meme'!

>@i80386sx

of course, who else would own every Compaq laptop 😀

The thing about Compaq is they loved reinventing the wheel. Almost every model has different expansion
https://github.com/raymondh2/CompaqPortableIII https://imgur.com/gallery/memory-expansion-co … ble-iii-MaBKUBc
https://forum.vcfed.org/index.php?threads/com … b-memory.79414/
LTE 5000 another different one, afaik no clones
LTE Elite aka 486s again different form factor 😀

rasz_pl wrote on 2026-06-14, 18:35:

/insert GTA San Andreas 'there we go again meme'!

Hehehe..

Indeed and Compaq definitely had too many engineers!

Don't forget Compaq Portable II extended memory recreation and my mini version 😉

sander wrote on 2026-06-14, 18:50:

Don't forget Compaq Portable II extended memory recreation and my mini version 😉

Wow nice, and soo compact!
btw github changed something about image links and clicking on "?raw=true" no longer just works unless opened in new Tab. Just went over my repos replacing all of it with direct links to https://raw.githubusercontent.com/...

rasz_pl wrote on 2026-06-14, 22:43:

btw github changed something about image links and clicking on "?raw=true" no longer just works unless opened in new Tab. Just went over my repos replacing all of it with direct links to https://raw.githubusercontent.com/...

Thank you for the heads up!

After having a closer look at the connectors on both the LTE (which I own) and the LTE/286, I've discovered a few things:

• The two extra RAS lines on the LTE connector are unconnected.
• There are no additional address lines, meaning 10 is the absolute maximum.

Based on a video by @i80386sx, there are two options for configuring expanded/extended memory. Here is why the missing RAS lines make sense:

• His RAM board is only populated on one side, and both RAS lines route directly to the unpopulated section.
• Because of this, he could only configure expanded memory.
• Therefore, those missing RAS lines are likely dedicated to extended RAM, which is exclusive to the 286 model.

On a side note: The current eBay listing for the RAM module shows a much better layout and is an original Compaq part. Even though it's only a 2-layer board, there is no need to populate both sides, which makes assembly easier. I'll go with this layout instead.

After analyzing the layout of the @80i386sx board, I've decided to go with the layout of this eBay module instead.

I've traced all the connections of the eBay board and uploaded my work to GitHub. Although the eBay product images are pretty low quality, everything fell into place since I already had a preliminary pinout. I was actually able to verify my work thanks to the reverse engineering I previously did on the @80i386sx board.

What's left to be done:

• Measure the slot dimensions and apply them in KiCad
• Clean up the schematic (renaming connections, add caps, etc..) and PCB design
• Double-check the resistor connections (I've asked @80i386sx to verify these with a multimeter)
• Convert the PCB into a 4-layer design
• Prototyping and testing this design

The Edge Connector Hunt:
Last but not least is finding a proper edge connector. The only suitable model I could find is this 'WingTat' connector on LCSC. Unfortunately, it's currently on backorder with no ETA.

On the bright side, there is also a 26-pin variant in backorder. I can use it for an ESP32/ESP8266 modem extension board project I'd like to tackle next!

sander wrote on 2026-06-15, 09:33:

Based on a video by @i80386sx, there are two options for configuring expanded/extended memory. Here is why the missing RAS lines […]
Show full quote

Based on a video by @i80386sx, there are two options for configuring expanded/extended memory. Here is why the missing RAS lines make sense:
[*]His RAM board is only populated on one side, and both RAS lines route directly to the unpopulated section.
[*]Because of this, he could only configure expanded memory.
[*]Therefore, those missing RAS lines are likely dedicated to extended RAM, which is exclusive to the 286 model.

This sounds weird to me, Expanded vs EMS is a function of chipset/mapper, not memory controller. Nobody builds separate memory controller sections just for different logical ram mapping. Is there a diagram available for LTE? what chipset is it using? knowing Compaq it will be something homegrown made by VLSI with no documentation 😐 The only lte/286 motherbaord picture I ever saw was in one of i80386sx videos for just a fraction of a second 🙁

https://www.minuszerodegrees.net/manuals/Comp … %20revision.pdf lists
1 MB Mem 001331-001 117266-001 LTE/286
2 MB Mem 001331-002 117265-001 LTE/286
4 MB Memory 001331-003 125656-001 LTE/286
one on the picture doesnt have any of those markings nor Compaq branding so third party?

I would look closer at the mobo. Maybe its based on a documented chipset and you will be able to figure out max capacity and optimal configuration this way.