Monday chores seemed to expand to 3x the usual, so didn't get long this evening. Spent my retro time assembling sundry support "stuff" that I might be needing in tackling the parity error on the PB800 board. If you've got any clues as to narrowing it down, I'm accepting your 2c here ... NEAT chipset memory problem on PB800/900 rev D 286 board....
First up, just grabbing a fresh set of picks for poking, prying and scraping, some turned pin socket headers because I haven't found any sockets yet, a 74LS280 I found in the logic bin, parity generator doohickey, I haven't found a discrete one onboard yet, but if there's a chance teh parity circuits are pooched, then I miiiight be able to jury rig something with that deadbugged to it. To the right, SIMMs I am gonna be grabbing the chips off, they are a match I think, though I notice they have had the backside nubs shaved so might not have as much pin on them as is usual, but they're standing off the board a bit so can't be too bad. The PSU hah, yeah, that one lost a fight with a can of tar based sealant, it was stored on the same surface, the can leaked, it got covered... That was about 15 years ago, wiped the worst off then, but it took a decade for it to dry to merely a bit tacky in the thicker parts. I guess I could have dunked it in kerosene or something, but at least it's more rustproof 🤣 Then of course we need a proper motherboard tray for the test bench, so there's a slab of wood to nail it to.
Boards, the 286 at the back is the Concorde boarde, mainly I got it out to threaten the PB800 board that it could be replaced and make it behave, and to maybe borrow it's 286 if required. Then a FIC 486-VC the big one, for main tester of SIMM and maybe other boards as required, maybe will have a trident testing individual, well pairs, of RAMs. Maybe a Trident will end up with the bad one, if it's a single pixel above 768k I'll see it basically never, okay yah, I'll pick one of my slow tridents for a high res windows card, sure. Anyhoo also got out a random ALI chipset board to make the FIC behave... or backup... Might need an ISA machine to run the EPROM programmer before we are done here too so one of those boards will serve.
The FIC fired up first try, just to POST screen, was about "done" for tonight. Oddly it complained Dallas battery was "low" but also seemed to be complaining about changed settings from when I last had it powered a decade back, 🤣 I guess that Dallas from 1993 still has a wee bit of juice in it, prolly not enough to keep time.
edit: ah okay, couldn't find that other board under Acer because it was an Asus ... https://theretroweb.com/motherboards/s/acer-i … gxi-model-i433a
Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.