This is not exactly correct. LPX standard was loose, but it defined a motherboard size. They also use an IO shield around the ports, it is just a thin strip because the ports are all just horizontally. This same idea carried over to ATX and you can actually fit most LPX motherboards to other LPX cases without any problems.

The problem with LPX as far as the compatibility goes was that it was so loose in other places. Riser cards weren’t standardised and there wasn’t a single LPX PSU standard. Some used AT PSU, but often it was fully proprietary with even proprietary power connectors to motherboards and power switches.

There are many good things with LPX too and that’s why many of it’s ideas were combined with AT when ATX was created. One is high level of IO integration to motherboard. Although LPX cases have only few expansion slots, you also had many features on the MB already often including graphics, so you don’t need huge amount of ISA or PCI slots. It is also very compact compared to full size AT. Most LPX style computers also had PS/2 ports for keyboard and mouse which is very handy.

I have two 486 Compaqs from this era as well as one HP Vectra VL2 486 and Tulip Pentium 166MMX LPX computer in my collection. I have sort of soft spot for Compaqs, but I like them all. The compactness of the systems is awesome for storage and desk and expansion capabilities have been completely adequate, although some of them do have all their slots filled. I for example install NICs by default (Tulip has on board NIC), intelligent mode MPU-401 cards etc. I also have IBM PS/2 model 35SX, which is ”LPX like” and those IBM computers worked as sort of inspiration for LPX design. All these LPX systems are of very high quality and built like tanks and they easily carry my heavy 19” CRT monitor.

You of course can’t usually install AT or baby AT MBs in these, but that is to be expected. If your jazz is to switch different MBs to the case or you want to make an old school AT build having everything on separate cards, then these type of systems aren’t for you.