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The RAM card listing in my shop has been updated with a dropdown. Basic: No switches, always 7 megs of RAM (Except M5126, that one sees 3 without a jumper wire) Switchable: Reworked boards similar to the above picture, until I run out of these and then all in the future will have the switches by...

OK, the mod boards arrived and they look pretty nice. 4 wires to points on the card and it presents the four RAM size modes listed before.

Assuming the issue is caused entirely by the size of the expansion card, yes. It should have the exact same problem. Or in other words, the Portable seems to slow down with expansion RAM cards above a certain size due to what is either a hardware or software bug in the Portable itself.

Mod boards have shipped, once those arrive I'll test the updated firmware some more and update the listing again. I already changed it to point at this thread for clarity on the speed decrease. Likely will have two options after testing, "Plain" and "Switchable". Then going forward, future...

Yeah, no need to rework the whole PCB when there are only a few pins that need tweaking. Future revisions of the RAM card (if they ever sell out) will have the switches by default.

This design is a "modboard", so it would be glued to the main PCB and then it's just four jumper wires. There's no need to order new "full PCBs" since I can just reprogram the CPLD and use a few more of its input pins as configuration.

I have started work on an alternate firmware and switch-mod-PCB for the RAM card. This will allow switching between the following modes: * M5120 "Low RAM" (4MB on expansion card) * M5120 "High RAM" (7MB on expansion card) * M5126 "Low RAM" (3MB on expansion card) * M5126 "High RAM" (7 MB on...

PDS probably doesn't have the perf penalty, because a PDS expansion card would be able to trigger EXT.DTACK independently of the glue logic.

I have now worked through the scenarios and these are my discoveries on the M5120 Portable: * Upgrade card set to 4MB or less: No perf degradation (no degradation after sleep) * Upgrade card set to 5MB or more: Perf degradation (worse after sleep) So it looks like for some reason or another...

It also depends on whether people want an update. Based on all my investigation, there's nothing wrong with the RAM card. It's performing exactly as it should. All these side effects of increased overhead due to memory management and the bug in CPU wait states are from things that are not...

I don't know if there's an easy way for you to flash the update. This is something I'd have to look into, because it's not friendly or convenient like an STM32 or Raspberry Pi Pico. This CPLD uses JTAG for flashing, which is a lot less common.

Overall it appears that any slowdown after a cold boot is probably due to system overhead with the memory manager. The strange behavior after sleep is because of a bug with the glue chip's wait states. My next step is to tweak the firmware again to increase available memory and see where the...

I created a "quick and dirty" test firmware for the CPLD. It reports as 3 megs of expansion (but provides 3.5mb because chip select logic is complicated). The Portable doesn't know what to do with half-meg increments and generally leaves it alone. The results? 2.08 CPU performance rating...

Ah, so it's the cpu glue which controls that. Is there a register or address reference available?

This is... odd. RAM access on the 68000 is controlled by the /AS pin (noted "AS" in the pictures because my analyzer didn't want to let me add a "/"). It means "The address on the bus is valid and the CPU is selecting whatever is there". Normal /AS cycles look like the above images, about 4...

Started investigating, was curious whether something was up with the RAM timing. The original spec is 100 nanosecond RAM, Techknight's 8 meg card used 55ns and mine uses 70ns. This doesn't appear to be related at all. Below are screen captures from my logic analyzer, with my 8 meg card on top...

Well, I'll be taking a look at this to hopefully duplicate and try to fix.

The hybrid module is probably not at fault here. The hybrid sends a signal to the power manager chip which indicates battery level. And the power manager chip sends a signal to the hybrid to tell it whether -5 volts should be generated or not. If that battery level signal droops too low your...

I think it's pretty unlikely that the hybrid could be a cause of this issue. Assuming the power LED comes on to the BlueSCSI after exiting sleep, it's not a power issue.

I use a Hakko desoldering tool from under the main portable PCB. The pins are pretty skinny, there's a lot of solder around them. Correct, replacement hybrids include new pin headers.