Multiple printers with defective 16MB DIMM

[The-Dude]

Over the last couple of years, I have acquired 4 used Hewlett Packard 4100 printers, in various condition,  to make 2 good printers. I just happened tp notice that on the Configuration Page > Installed Personalities and Options (for all 4), they show the standard 48MB of memory  installed in the DIMM slots: a 16MB and 32MB card. However under Memory > Total Memory it shows only 32MB. Identical for all 4 printers, which I bought, or was gifted, from 4 different sources. I swapped out the 32MB one in one of the printers, for another 16MBcard from another printer. When I turned on the printer, the screen in the Control Panel was illuminated but blank, which is how it looks if you remove all DIMM from the printer. I guess they are dead, but it seems hard to believe that all 4 16MB cards (exclusively) would be so, especially when you can find lots of supposedly used but working ones on EBay. And why would they still show up as installed in the DIMM slots if they are dead? This isn't really a desperate plea for help, more of just a nagging mystery. Does anyone have any ideas?       

[Valsimot · Accepted solution]

It has been a while since I worked on 4100 series but as I can remember HP Laserjet 4100 uses 16MB flash DIMM that is different from 32MB memory DIMM.

That one slot on the formatter board can be used only for 16MB flash DIMM, if you remove 16MB flash DIMM, and install memory DIMM printer will not work. You have 2 more slots for adding memory DIMM up to 256 MB ( 2X128MB).

Keep 16MB flash DIMM on formatter and instal 2x32 MB memory DIMM and check for total memory.

[The-Dude]

Yes, I see now that I missed that next to "16MB" in "DIMM Slot 1" it reads ROM instead of SDRAM. I assume that indicates flash. I guess I was thrown off by the users manual, where it reads:

   Printer memory and expansion

Overview
The printer has three dual in-line memory module (DIMM) slots
for upgrading with:

more printer memory—DIMMs are available in 4, 8, 16, 32,
64, and 128 MB, for a maximum of 256 MB

flash memory DIMMs—available in 2 and 4 MB; unlike
standard printer memory, flash DIMMs can be used to
permanently store downloaded items in the printer, even
when the printer is off

DIMM-based accessory fonts, macros, and patterns

other DIMM-based printer languages and printer options

It shows a 16MB DIMM, but no flash larger than 4MB

Thank you for you help!