I recently acquired an "as-is" TRS-80 Model I Expansion Interface (final board design) that arrived containing a total of 32K of DRAM, and everything looks really clean an in good shape (capacitors, etc.).
The DRAM is a mixture of the following chips with a wide variety of date codes:
The EI is acting a bit flakey (lockups, reboots, various amounts of RAM reported if I get that far), so I wanted to start by making sure that I have the correct type/speed of DRAM installed. I believe that D416C-3 is a good match (150ns), but I'm having trouble finding the data sheets (or any info) on the other two parts. I believe the -3 in the NEC D416C-3 indicates 150ns, and I have seen that -2 is supposed to be 200ns. But on the NEC parts without that last number, I'm not sure how to determine the speed. And I don't see info on the Motorola chip anywhere I have searched.
Question #1 - Can anyone here confirm whether these are all valid chips to use in the Expansion Interface, whether it's okay to mix/match them in the same EI, and if you know where I could find datasheets for these parts?
Question #2 - Does anyone know where I could find a relatively low-cost stand-alone DRAM tester for these parts (or a kit or schematic from which I could build one), so that I could test the chips independently from the EI unit? I'm having trouble keeping the system from locking up or rebooting before I can get any meaningful software-based DRAM testing done in the EI itself, so I'd like to be able to test the DRAMs separately. (I see a lot of SIMM DRAM testers, but haven't found one that deals with these chips.)
Thanks.
The DRAM is a mixture of the following chips with a wide variety of date codes:
- NEC uPD416C
- NEC D416C-3
- Motorola 8041016
The EI is acting a bit flakey (lockups, reboots, various amounts of RAM reported if I get that far), so I wanted to start by making sure that I have the correct type/speed of DRAM installed. I believe that D416C-3 is a good match (150ns), but I'm having trouble finding the data sheets (or any info) on the other two parts. I believe the -3 in the NEC D416C-3 indicates 150ns, and I have seen that -2 is supposed to be 200ns. But on the NEC parts without that last number, I'm not sure how to determine the speed. And I don't see info on the Motorola chip anywhere I have searched.
Question #1 - Can anyone here confirm whether these are all valid chips to use in the Expansion Interface, whether it's okay to mix/match them in the same EI, and if you know where I could find datasheets for these parts?
Question #2 - Does anyone know where I could find a relatively low-cost stand-alone DRAM tester for these parts (or a kit or schematic from which I could build one), so that I could test the chips independently from the EI unit? I'm having trouble keeping the system from locking up or rebooting before I can get any meaningful software-based DRAM testing done in the EI itself, so I'd like to be able to test the DRAMs separately. (I see a lot of SIMM DRAM testers, but haven't found one that deals with these chips.)
Thanks.