Thread by @RetroTechChris

Recently I updated the BIOS on my Compaq LTE 5400 to support large hard drives. However, this ended up causing a few other issues I had to solve. Anyone remember battling with DOS conventional memory and dealing with driver issues? Well... here we go! 🧵

As I noted in the opening post, I upgraded the BIOS. This upgrade basically adds XTIDE to the system to support large hard drives. But, XTIDE is what is known as an option ROM. Which means that it is going to take a slice of the "upper memory area" in order to work.

This caused two issues for me. First, my PCMCIA network card tended to "live" in the region that is now used by XTIDE. Okay, no problem. This computer uses SystemSoft software to manage PCMCIA. Through trial and error, I moved its memory region elsewhere. Network card fixed!

Also, since the SystemSoft software loads late in the system bootup sequence (after EMM386), we need to exclude its new memory region so that it doesn't get trampled. That's easy enough to do as well. Perfect!

With that out of the way, I thought I'd do the "Commander Keen" test since, I figured we probably wouldn't have enough conventional memory to run it anymore. Why? Well, that XTIDE option ROM takes upper memory blocks, so less items can be loaded "high" on system boot.

I spent the next several hours beating my head against the wall a little. I even installed QEMM to see if I could free up some conventional memory. I tried MemMaker too (not shown). In the end, I just fixed everything myself by hand.. I'll explain how!

One would think: just load everything "high". But what I found is that with a 20K "high" block free, my network card driver (14K) would still load "low" and waste upper memory blocks. In the end, I "fixed" this by purposely loading the CD-ROM drivers low in config.sys!! Fixed!

I actually had to do one more trick here since memory was so tight. I swapped out MSCDEX (basically Microsoft's driver that gives your CD-ROM a drive letter) for SHSUCDX (an open source variant of MSCDEX). I popped a CD in the drive and it seems to load up just fine!

So, yes, with this we are good to go. I took the opportunity to reload Windows for Workgroups 3.11 in the process here as a part of troubleshooting too, always good to have a fresh install!

I'm sure that not many people miss the days of IRQs and fussy device drivers, but I really enjoy solving puzzles like this. Here's my final config.sys and autoexec.bat files. I should be good until I make the next system change, I guess! Thx for reading.

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