All right, so I had a bit of a mishap today. So I have this Compaq Presario 1700 17XL365 laptop that's I recently got into an operational state (at least as a halftop with a very nice external monitor cause the hinges were GONE) and something a little bit weird happened. So I needed to upgrade the RAM from 256MB to 512MB cause I want to be able to use a VM or emulator under Windows XP in order to try and shoehorn some really slimmed down versions of Windows 7 and a de-PAE/NX-ed version of Windows 8 that I have onto this thing due to the questionable ACPI support giving me issues on bare metal, along with just wanting to use newer versions of Office and other software without frying the SSD out with heavy virtual memory usage. Well inside it there is a KTI 256MB SDR133 module with small BGA chips on it, and I thought that SDR133/PC133 is gonna be what I needed to look for. I'd seen some highly confusing mention online about SDRAM density issues on some laptops but having rarely had memory compatibility issues on DDR era systems I thought this must be some weird fluke some computers had or whatnot. Well my large order of new generic PC133 modules with large roughly DDR1 non-BGA variant sized large chips came in today and I got all excited only to be be met with... failure. So I tried each of three brand new memory modules alone in each slot. Nothing. Two modules together? NOTHING. By "nothing" I mean black screen signal being actively sent to monitor, so literally mid-post failure without tripping a beep code. Ok cool I think, maybe this stupid thing is being picky (or heaven forbid has some kind of module-restriction DRM) like the time I tried to put 3200MHz aftermarket DDR4 in my main rig where it only even posts if I mix it with a 2667Mhz module cause of the OEM's BIOS restrictions. I mix a module of this new stuff with the old KTI module and depending on bootup attempt, I'd either get the black screen, Compaq logo followed by black screen or a pci.sys file corruption error from Windows Fundamentals for Legacy PCs. Evidently these new modules are able to talk the memory controller but are just corrupting the data. As a sanity check I made sure again the stock (to me at least, unsure if its what came with this thing from factory cause there was traces of old shoddy repairs galore on this machine when I got it) KTI module works in both slots and it does. Am I missing something here with this whole low/high density thing as the seller claims, or did the seller sell me faulty RAM?

I thought I knew damn near everything about most typical RAM-related computer repair situations cause of some RAM/CPU interaction related stuff (not allowed anymore to talk online about it) I did in my college years that literally got me into a CPU manufacturing career, but I'm less experienced with pre-DDR stuff so unsure if I am missing something 🤣.