How 2MB chip ram with the Mini Megi Chip?

[Antti]

I bought one of those NTSC Mini Megi Chips from Vesalia for my A500 (PAL). The installation guide was in german so it was quite difficult for me to understand it fully, but with a little help from Google translator I managed to get the chip installed. As it's stated in the guide, the trapdoor memory expansion needs to be turned off. I proved it to be true because my A500 didn't boot if it was turned on. Now I've got 1,5MB chip ram, so how can I get the full 2MB if I can't use the trapdoor expansion?

I have a rev6 mb and the memory expansion card is a 512kB Roctec RM550C.

[Jope]

Did you have 1MB chip on the machine before? If you had 512/512, then you need to do the 1MB chip mod first.

[alexh]

Originally Posted by Antti

I bought one of those NTSC Mini Megi Chips from Vesalia for my A500 (PAL).

Did you fit a PAL 8375 2Mbyte Agnus to the Mini Megi? Or are you just using the NTSC one?

Originally Posted by Antti

I've got 1,5MB chip ram, so how can I get the full 2MB if I can't use the trapdoor expansion?

If you only have 512Kbytes Chip RAM on your motherboard I am pretty sure you've got to modify your motherboard in order for your 512Kbyte trapdoor RAM card to function or add more RAM to the motherboard. You need to read up.

http://aminet.net/search?query=agnus

9b. FOR A REVISION 6 AND ABOVE AMIGA 500 WITH 512K CHIP RAM:

[ ] 9.13 Locate JP2 on the left side of the 40 pin ROM socket. Using
a sharp X-Acto Knife or similar item cut the trace connecting the
bottom and center pads. Then solder the top and center pads together.
Doing this will enable the A19 line from the 68000 to the Agnus
socket. Go on to the next step.

[ ] 9.14 Locate jumper JP7A to the left of the CNX expansion bus
connector. Using a sharp X-Acto Knife or similar item cut the trace
connecting the bottom and center pads. Once this trace is cut you do
not have to do anything else to this jumper. Make sure you do not cut
any other traces on the motherboard. Go on to the next step.

[ ] 9.15 If you do not have a 512K RAM board plugged into the CNX
expansion bus (the belly slot under the 500) you must do this now. At
this point your machine is compatible with the 1 meg Agnus and 2 meg
Agnus board.

[Antti]

@alexh: I'm using the NTSC one. Yeah, it's a bit frustrating to go to early startup menu on each cold boot...

@Jope & alexh: I already had modified the mb for 1MB chip, but I'm pretty sure I couldn't get the A500 to boot if the mod was enabled. By not booting I mean the screen remained black when I turned the power on. But I'll give it an another try when I get back home. I've soldered jumpers on the mb so it's quite easy to test again

[alexh]

If it doesn't work. Double check that your mod is correct.

[Antti]

Well, what do you know: It does boot after all! I must have had a loose connection somewhere yesterday Thanks for the help

[Amiga_CDTV]

Old thread but still: thumbs up

I bought a Mini Megi board and I just finished modding the board as instructed here: now I have 2 MB Chip Ram, and a working RTC (as I replaced the battery inside the A501) in my A500. Nice!