[Video] DFB1r4 pre-Christmas update

[mrbombermillzy]

Hey @Steve No worries. Honestly, we are all friends here. I'm just *passionately* providing reasons 'for' the extra memory.

I'm sure @Badwolf will chip in sooner or later to provide the final word to put end to all this anyway....that's if we haven't upset him too much with the thread derail!

[Badwolf]

Hi guys.

Thanks for the feedback. Amusing to catch up on it as I've been away for a few days.

One of the driving factors behind this project was I was annoyed the modern Linux kernel had evolved beyond being able to boot on the Falcon so I wanted more memory, so I'm not offended by the suggestion of bunging 3 GB in it, or whatever.

For this particular design however, it would need to be two chips of 54 pin TSSOP SDRAM in the conventional configuration. It looks like the highest capacity ones that Mouser and Farnell stock are 512 bit -- ie 64 MB each => 128MB total is the best you're going to get out of this.

Screenshot 2021-12-20 at 17.20.14.png (143.93 KiB) Viewed 1652 times

Screenshot 2021-12-20 at 17.17.24.png (276.75 KiB) Viewed 1652 times

Now, if you're a dab hand with a soldering iron and don't mind a little bit of diving into the verilog, you could probably just about piggy back a second set of chips onto this and break out the appropriate DQM pins, wiring them to the spare pins provided (although I'm no longer sure there are actually enough for that). That would bring the absolute theoretical maximum to 256MB (+14 on board). Completely left as an exercise for the reader, however.


BW

PS: of course the ultimate irony now that I have a stable product is that BOOTSTRA.TOS, the Linux kernel loader, hangs on reset with my board enabled. I need to try NetBSD again.

[czietz]

PS: of course the ultimate irony now that I have a stable product is that BOOTSTRA.TOS, the Linux kernel loader, hangs on reset with my board enabled.

I vaguely recall a similar effect on my TT when running Linux. Iirc, I ended up loading the kernel to ST-RAM, via the "-s" argument to BOOTSTRA.

[Badwolf]

I vaguely recall a similar effect on my TT when running Linux. Iirc, I ended up loading the kernel to ST-RAM, via the "-s" argument to BOOTSTRA.

Thanks, Christian. I did a quick check but have that turned on already. It doesn't work even when in unaccelerated ST-RAM-only mode either, so it must be doing something funky my card's not able to handle.

It's not a high priority, but it's a reminder that I've many rabbit holes to go down one day!

BW