exxos's Atari, Amiga & retro forum

Just want to make sure before I start digging into the MB, which resistors do I need to pull up to 5V, and what would a good 5V place be? 1040STF, C103225 Rev 2. I've attached a picture...

Also, once all tested and working great, do I simply unsolder all the RAM chips, or do I have to do anything else?

Thanks!

I would just pull up the right side of all the 68R resistors and tie them to 5v . a easy place is the left side of the big cap..

Once working , remove all the old ram, or just remove it anyway.

According to other reports it is enough to unsolder the big inductor (L1 - left edge, just above the DRAMs and a big axial capacitor) which powers the DRAM chips. I know it seems bad to leave unpowered ICs on the bus, but apparently it works fine with DRAMs.

tzok wrote: 11 Aug 2020 10:19 According to other reports it is enough to unsolder the big inductor (L1 - left edge, just above the DRAMs and a big axial capacitor) which powers the DRAM chips. I know it seems bad to leave unpowered ICs on the bus, but apparently it works fine with DRAMs.

Whilst this is certainly possible, instructions for every RAM upgrade I've ever seen all say to tie the resistors to 5v, so I would go with that as the preferred method, and ideally remove the old RAM as @exxos suggests once you are happy the upgrade works as expected.

exxos wrote: 11 Aug 2020 02:04 I would just pull up the right side of all the 68R resistors and tie them to 5v . a easy place is the left side of the big cap..

Once working , remove all the old ram, or just remove it anyway.

This has made me wonder if the old ram should be removed after marpet installation?

If you don't cut the power from it, they will still consume a decent amount of power and produce heat. So I think it is worth to remove them completely (or just cut their power line as it is easily separable).

The cut resistors to 5v has been done.

Cosmic Puppet wrote: 11 Aug 2020 11:30

exxos wrote: 11 Aug 2020 02:04 I would just pull up the right side of all the 68R resistors and tie them to 5v . a easy place is the left side of the big cap..

Once working , remove all the old ram, or just remove it anyway.

This has made me wonder if the old ram should be removed after marpet installation?

Yes, despite the 5v to disable them, you will still consume power as long as the old RAM is installed. If you're happy to do so, then removal is the way to go with any of the MMU/Shifter based adaptors, Marpet, exxos, any of them.

However I do have one which is MMU/Shifter based that is only 2MB RAM and expects to find the original 512KB there, for an overall 2.5MB of RAM. In that case you wouldn't want to disable or remove the old RAM.

Learnt something new today. I have the opportunity to have it removed, so if it's needlessly consuming power...

Don't ever cut power to chips and power them up, you can blow stuff up doing that, disable them properly by disabling them with the resistors, or just remove them.