I had not appreciated the different types and costs of memory expansion that are available before I purchased my A1200. I should have done some research first - some good information can be found on this thread on AmiBay. and a comprehensive list of Amiga hardware, including expansion options can be found at www.BigBookOfAmigaHardware.com.

AmiBay describes itself as "The Retro Computer Trading Post", which may be true, but its forum rules prevent general pricing discussions and trades are pretty much fixed price, rather than auctions. This makes it a bit difficult to estimate the market price for a given upgrade, but a quick look at the posts there show that a RAM upgrade can cost anywhere from around £30 to close to £1000, so, how do I know what I need?

PCMCIA RAM Cards

A PCMCIA slot was added to the Amiga range with the A600 model, in the A600, as might be expected, the addition of a PCMCIA RAM expansion resulted in a performance increase. The PCMCIA slot is compatible with PCMCIA Type II memory and is therefore limited to 16-bit memory, the same as the A600's main RAM, 32-bit PCCard or CardBus memory cannot be used.

Since RAM made available via the PCMCIA card slot is accessible by the CPU, like the other RAM expansion options, it is referred to as "Fast RAM", but, in the case of the A1200, this is something of a misnomer. Like the A600, the PCMCIA slot in the A1200 is Type II compatible and therefore limited to 16-bit memory. When "Fast RAM"  is added to an A1200 using the PCMCIA slot, system speed is actually degraded, therefore, this is obviously the least preferred option for expanding the RAM.

When I first looked at RAM expansion, before I was aware of the limitations of using the PCMCIA slot, I found that they are not a cheap option either. The memory card needs to be SRAM and even used 2MB SRAM cards seem to be around £40.

Trapdoor Expansion Connector

The A1200 has a bus expansion connector on the system board which is accessed through a removable cover in the bottom of the case - the Trapdoor , the Trapdoor interface allows access to the main CPU bus and supports up to 32-bit RAM in either of two ways,  both of which can prove to be costly - in fact eye wateringly so ! 

RAM Expansion Boards

The A1200 CPU is a Motorola 68EC020, a low cost version of the 68020, both are 32-bit processors, but, whilst the 68020 has a 32-bit address bus, allowing up to 4GB of memory to be addressed, the A1200's 68EC020, with its 24-bit address bus, can only access a maximum of 16MB of RAM, 8 of which can be installed on a Trapdoor expansion board.

More details soon, when I get over the shock!