exxos's Atari, Amiga & retro forum

How fast are the ram chips on the memory expansion?

Use 100ns or even better 80ns or faster if you do want to place the memorychips on the mainboard.
Make sure the keyboard still fits if you are using sockets.
As I mentioned before, you will not be able to use some expansions (memory expansions and more) after this mod.

Can you show some pictures of JP2 and JP7a?
(if it is already modded for 1mb chip mem and there is 120ns ram on the expansion, this could be a reason for the ram errors)

Maximilian wrote: 02 Feb 2025 01:02 How fast are the ram chips on the memory expansion?

I'll check and post back, but it is a fairly standard 3rd party trapdoor RAM/RTC card so I'd expect the RAM to be a suitable speed.

Maximilian wrote: 02 Feb 2025 01:02 Use 100ns or even better 80ns or faster if you do want to place the memorychips on the mainboard.
Make sure the keyboard still fits if you are using sockets.
As I mentioned before, you will not be able to use some expansions (memory expansions and more) after this mod.

I think I have 80ns RAM, so that should be fine, but I'm not yet ready to go down that route. I did wonder if the keyboard might be a problem with sockets for the RAM, thanks for confirming it could and I'll test before assembly if I go down that route.

As it happens, RetroLemon are getting stock of the Lotharek 8mb/IDE upgrade that fits under the CPU so it may be unnecessary anyway.

Maximilian wrote: 02 Feb 2025 01:02 Can you show some pictures of JP2 and JP7a?
(if it is already modded for 1mb chip mem and there is 120ns ram on the expansion, this could be a reason for the ram errors)

I will get some later on, but they appear to be in their factory positions and untouched at the moment.

Appreciate your help, thanks.

@Maximilian

The trapdoor RAM is 120ns and I have 100ns and 60ns RAM that I can fit on the mainboard if I decide to do so.

Pictures of jp2 and jp7a to follow later.

stephen_usher wrote: 01 Feb 2025 23:08 If there's no RAM there and you're only testing the SLOW RAM addresses then the machine should not crash but the memory test should fail. You are manually testing only 0xC00000 to 0xD7FFFF aren't you?

That memory range is interesting, on the memory map I looked at it didn't say that range so I'll recheck.

Maximilian wrote: 02 Feb 2025 01:02 Can you show some pictures of JP2 and JP7a?
(if it is already modded for 1mb chip mem and there is 120ns ram on the expansion, this could be a reason for the ram errors)

JP2 and JP7a:

JP7 is a red herring as that's purely external real time clock related and isn't connected to the memory sub-system at all.

stephen_usher wrote: 02 Feb 2025 12:42 JP7 is a red herring as that's purely external real time clock related and isn't connected to the memory sub-system at all.

Well it's a bit of a moot point anyway as its set to default anyway.

As it goes the RAM card has a jumper connected to there and it can be turned off if required.

The RTC is visible to ATK anyway, so it has to be memory related.

rubber_jonnie wrote: 02 Feb 2025 08:48

stephen_usher wrote: 01 Feb 2025 23:08 If there's no RAM there and you're only testing the SLOW RAM addresses then the machine should not crash but the memory test should fail. You are manually testing only 0xC00000 to 0xD7FFFF aren't you?

That memory range is interesting, on the memory map I looked at it didn't say that range so I'll recheck.

No real difference using that range. Crashes quick and has to be rebooted.

stephen_usher wrote: 02 Feb 2025 12:42 JP7 is a red herring as that's purely external real time clock related and isn't connected to the memory sub-system at all.

It was probably meant to be JP3 but that is set as default as below.

rubber_jonnie wrote: 02 Feb 2025 14:38 No real difference using that range. Crashes quick and has to be rebooted.

Something is very wrong there then.

Maybe one of the higher address lines isn't behaving correctly somewhere so writing to a location where nothing is supposed to be is changing something at a lower address where something important lives.