Hi there everyone! Long term lurker, first time poster, here!

Recently I've been bitten by the DOS bug and have gone out in search of a nice system to both play old DOS titles on, and also have proper period correct compatibility with all the sound cards I may wish to use. It took me a bit but eventually I ended up with quite a few different machines and pieces of hardware. Thanks in no short part to everyone on here as well while I lurked around and learned everything I could from here in my search.

While I managed to find a couple of Pentium machines (all P2's & P3's) and got everything up and running my holy grail was an attempt to find myself a really nice 'slimline' style system similar to the Unisys CWD line. As I prefer to find my hardware locally whenever possible this lead to a lot of fruitless searching until finally I bumped into a pair of DIGITAL DECpc LPV+ 425SX machines at my friend's old record shop. He was clearing out his back room and had long since thought that all of his original POS terminal PC's had been sent off to the recyclers. Lucky for me I got a matching pair of units so I have a complete set of spare parts. Also including the ability to steal the extra memory/zip chips off of one to upgrade the video RAM on the integrated S3 S3 86C805 (should be on an integrated VLB bus if I'm correct) from what I've seen. Both are 486SX's running at 25mhz, have 4MB of ram, one 615mb HDD, one 1gb HDD, and the bundle included 1 matching DIGITAL branded monitor and several mechanical Cherry branded keyboards (some with card readers, 🤣). Aside from having some very dusty innards they both seem to be working perfectly so far, and support 50MHZ 486 upgrades. However, when I tried upgrading the RAM from the stock 4MB I was greeted with several error messages and lots of angry beeping.

The DIGITAL brand, with 'Digital' meaning made by the Digital Equipment Corporation, which makes searching for info even harder as you won't get very far beyond generic results when looking for a 'digital' computer, 🤣. According to the information I've managed to find while looking at online these machines should support up to 32MB or 64MB of ram at maximum and only through either 72pin 4MB or 16MB simms with a latency of 70 or less. However whenever I add any of my existing 4MB Simms it refuses to boot, 8MB simms that meet the relevant requirements show up as 4MB simms along with the original one that came with the machine. Unfortunately I have no 16MB simms to check with compatibility wise. Secondly, the machine has started giving me 'Incorrect memory configuration' errors even with the original NEC branded ram stick installed back into place. I'm not sure where to go from here, and am completely and utterly lost in terms of what I'm doing as I grew up in the Pentium era. As a total newbie to anything 486, XT or AT it's a bit like incomprehensible black magic and incredibly rare here in NC. As a total newbie to these machines anything 486, XT or AT is like incomprehensible black magic and incredibly rare where I am, so any help would be appreciated.

I was unable to find ANY support for these online anywhere which is disappointing. According to some sources on a few forums Compaq used to have all of these drivers available as a part of their legacy support site as recently as 2010-2012 (Compaq/HP bought out DIGITAL in the mid-90's), but I had no such luck finding any. When I went around following any of the links I found on various other forums, and even going so far as to call HP/Compaq's support number, I pretty much hit a dead end. I was hoping to update the BIOS as it seems that there were several revisions thanks to both an archived eBay listing which shows a picture of a 1.04 BIOS (mine are 1.00) and the service manuals stating the maching accepts up to 64MB of RAM. The service manuals were both printed in 1996, a year after the computer's release, but make no mention of either the BIOS or anything else when stating upgrade capacities. So, I'm hoping someone on here can either help me out and potentially proivide BIOS upgrade files, or tell me what I need to look for when it comes to RAM or anything else.

Also, these machines use a clock 'chip' and not a traditional lithium/coin battery. How exactly does oner go about replacing these? Can they go bad and/or explode like older AT and ATX batteries, or are they driven by some sort of long-term charge, etc...?

Finally, I have attached both the service manual, and service guides, for anyone who is interested in helping out to have all the most complete information I could find. Any advice or info would be appreciated and I'm looking forward to whatever help anyone on here could provide!