A1200 RAM expansion

[PeteJ]

I bought a Magnum RAM8 board for my A1200 recently. It was supposed to have 4Mb installed on it but I think Sysinfo shows that it actually has 8Mb? Or is that my expansion ram plus the system ram?

[liviux76]

That is only the Fast RAM so the expansion card has a 8MB RAM module. The Chip Ram on the A1200 is 2MB so now you have a Total of 10 MB of RAM (2 Chip + 8 Fast)

[PeteJ]

Originally Posted by liviux76

That is only the Fast RAM so the expansion card has a 8MB RAM module. The Chip Ram on the A1200 is 2MB so now you have a Total of 10 MB of RAM (2 Chip + 8 Fast)

That's great thanks

Does that mean the PCMCIA port will not be able to be used though?

[amigakit.com]

Hi PeteJ

The 8mb will map itself to the PCMCIA address area and block it's full use. So there will be jumper on the memory card to downgrade it to 4mb or 0mb Fast RAM. When set to 4mb or below, the PCMCIA will function normally. Accelerators in contrast do not generally have this same limitation with the PCMCIA port. Hope this helps.

[PeteJ]

Originally Posted by amigakit.com

Hi PeteJ

The 8mb will map itself to the PCMCIA address area and block it's full use. So there will be jumper on the memory card to downgrade it to 4mb or 0mb Fast RAM. When set to 4mb or below, the PCMCIA will function normally. Accelerators in contrast do not generally have this same limitation with the PCMCIA port. Hope this helps.

Thanks very much. That's an acceptable option for the ram expansion rather than removing it to use the PCMCIA port. I'll look up the jumper settings.

[amigakit.com]

Here you go:
http://www.bigbookofamigahardware.co...t.aspx?id=1025

[liviux76]

As far as I know, using 3.0 ROMs there are some chances that pcmcia slot and 8 MB of FAST RAM work together.
I had an apollo 1230 with 8 MB of RAM that didn't have any contrast with pcmcia slot when my system was using 3.0 ROMs.

[Daedalus]

@liviux76

It's got very little / nothing to do with the ROMs - A1200 motherboard space maps RAM expansions into the same area as PCMCIA memory - that's a hardware limitation. Your accelerator gets around that by having a separate CPU which has separate 32-bit access to the 8MB of RAM, and so can put it in a different address not physically possible using the internal CPU of the A1200, and that's why you don't have any problems.

[amigakit.com]

@Daedalus

Correct.

The A1200 RAM only expansions have a 24-bit address space which means that the PCMCIA address space clashes with the upper 4MB memory area. The small address space is a limitation of the 68EC020 CPU on the A1200 motherboard.

Most A1200 accelerators with full 680x0 CPUs (non-EC) have a much larger 32-bit address space so PCMCIA address space can still be used.

[alenppc]

The 3.0 roms do not disable the PCMCIA port when 8 mb are present in Z2 trapdoor space. Commodore labeled it a "bug" and "fixed" it in 3.1. However, turns out the functionality was better in 3.0 since you can still use network/CF cards even if you have 8 mb in Z2 space.

I downgraded the roms on one of my a1200s just for this purpose.

[PeteJ]

Thanks all, that's explains things perfectly.

So... with the memory only expansions and OS 3.0 roms the PCMCIA port is still active despite half of the expanded 8Mb memory mapped to that area. I assume that means that if the system is only using 4Mb or less whilst the PCMCIA card is in use it will function without issue? If I understand correctly also, with the OS 3.1 roms they have disabled the PCMCIA port automatically for memory only expansions that are >4Mb to avoid any issues occuring?

[fgh]

From the A1200 System Specification:
000000 to 1FFFFF 2 MB Chip RAM(or system ROM overlay)
200000 to 5FFFFF 4 MB Zorro II expansion space
600000 to 9FFFFF 4 MB Credit Card memory if CC present
AOOOOO to A1FFFF 128 KB Credit Card Attributes
A20000 to A3FFFF 128 KB Credit Card I/O
A40000 to A5FFFF 128 KB Credit Card Bits (similar to CDTV)
A60000 to A7FFFF 128 KB PC I/O

Only PCMCIA SRAM cards use the Zorro2 memory space.
Other PCMCIA equipment use Zorro2 I/O space that does not conflict with 8MB trapdoor RAM expansions.
Therefore you can have 8MB with KS3.0 and still use your PCMCIA for CF cards, wifi, etc.