exxos's Atari, Amiga & retro forum

It was a long time ago for me, but I remember that if you want to use WhdLoad from the HDD then you can run into some issues with some games if you only have 512KB chip.
Having fastram will help, but i would IMHO certainly do my best to get that 1MB chip up and running.

Maximilian wrote: 12 Feb 2025 16:50 It was a long time ago for me, but I remember that if you want to use WhdLoad from the HDD then you can run into some issues with some games if you only have 512KB chip.
Having fastram will help, but i would IMHO certainly do my best to get that 1MB chip up and running.

That's what I'm aiming for, it's just a question of how? Trapdoor or on the mainboard?

Of course I'm now wondering if the trapdoor RAM card I have has an issue since the onboard RAM and new 8MB fastram all test just fine.

Chipram and slowram(Agnus/Gary) are connected in a different way to the fastram(CPU) you added, having fastram work doesn't say anything about having Chip/slow ram working.

If you aren't going to use the trapdoor expansions with extra features like the KCS PowerPC board or the 1.8MB ram expansions then it should not be a problem to add the chips to the mainboard.

Keep in mind that there aren't a lot of differences to having a trapdoor expansion or putting the ram directly on the board.
If the onboard ram works you can reasonably presume that the trapdoor expansion or the connector/traces to the connector were the issue.

At this stage I would probably add the sockets and ramchips to the motherboard and change the jumpers to test, I would remove the trapdoor expansion before testing to make sure that it would not interfere.

Cutting jp2 and soldering the other two pads should be enough after adding the memory chips to get 1MB of chip.
(with no trapdoor expansion present)

If you really want to use the trapdoor expansion as a clock then I would remove the ram from it and use the disable jumper on the expansion (a501 has jp1), if there is no disable jumper you can unground pin 32 of the expansion header or change jp7 on the mainboard.

@Maximilian Thanks for the info, hopefully when the replacement Agnus arrives tomorrow I'll have more answers.

Maximilian wrote: 12 Feb 2025 18:06 If you really want to use the trapdoor expansion as a clock then I would remove the ram from it and use the disable jumper on the expansion (a501 has jp1), if there is no disable jumper you can unground pin 32 of the expansion header or change jp7 on the mainboard.

I'm always confused about this advice as according to the schematic JP7 has nothing to do with the RAM sub system and merely deals with the EXCLK signal.

stephen_usher wrote: 12 Feb 2025 21:42

Maximilian wrote: 12 Feb 2025 18:06 If you really want to use the trapdoor expansion as a clock then I would remove the ram from it and use the disable jumper on the expansion (a501 has jp1), if there is no disable jumper you can unground pin 32 of the expansion header or change jp7 on the mainboard.

I'm always confused about this advice as according to the schematic JP7 has nothing to do with the RAM sub system and merely deals with the EXCLK signal.

I assumed that was in reference to the clock as well. I assumed that meant if I was disabling the RAM on the expansion and then using the external clock, but it sees the external clock anyway with no mods.

It's not the standard 4 chip expansion as referred to in the schematics (Oddly called 'Cake') but has 16 41256 ICs onboard. I'm still not entirely convinced that the RAM isn't somehow dead, but hopefully the replacement Fat Agnus will be here tomorrow and if that changes nothing I have to suspect the trapdoor RAM board and TBH if I can't get it to work I'll just use it as an RTC board.

Also, if I can't get it to work I may just pull all the RAM and fit sockets as I have a load of 41256 ICs to hand. Then I'll test all the ICs from it and see if any are bad.

All the signals (RAS/CAS address/Data R/W etc) are there, it just can't be seen. A little more fun before I throw it all back together. Though saying that I do still have to settle on a version of Kickstart and Workbench to install on the IDE drive before I chuck the case on.

OK, so I want to get this A500 booting from HDD and from what I can see I need to use Kickstart 3.1 single ROM version and then I can use WB3.1 as I understand, which is handy as I have that on floppy.

Have I read that right?

No. If you bought the Lotharek 8MB+IDE it works with KS1.3+ and WB1.3+

It is not like other IDE interfaces which clone the A600 Gayle IDE controller. It is a different design with an integrated KS1.3+ compatible boot rom.

Most expansions use the same simple IDE setup as the A600 and the a1200, for that you would need at least a Kickstart 2.05 rom.
But it seems that your Lothatek expansion has a BSC Oktopussy ROM so it could even boot with Kickstart 1.3.

Ofcourse it would be better to get a Kickstart 3.2.2 rom and workbench 3.2.2.

I'm really interested to see what the fault is with the memory expansion, it is not common for an Agnus to break like this without physical damage.

Take a look at the A500 Rev 6 schema, check where the extclk signal goes.(hint Gary pin 32) and what that signal is called then.