ChipMEM and FastMEM on A500

[Iznougoud]

I recently dug out my old A500, and disassembling it, I noticed that there's room for another 4 RAM-chips on the motherboard. The motherboard being rev 6A, it supports a total of 1Mb ChipRAM, and having suitable RAM-chips, even an amateur like me could probably add another 512Kb to the motherboard.

Question is, what kind of RAM-chips would be suitable? Could I, for instance, take chips from a SIMM or EDO-stick, and if so - do they have to be the same size (i.e. 512kb/4)?

Which, in turn raise another question: The expansion-RAM for the A500. Is it possible to replace the RAM-chips the same way? From what I understand, the memory addressing is done by the machine itself, and for example for 2Mb-chips on such a board would theoretically mean the maximum of 8Mb FastRAM. Same question as before applies though, could such chips be salvaged from SIMM or EDO-sticks?

[rkauer]

Originally Posted by Iznougoud

I recently dug out my old A500, and disassembling it, I noticed that there's room for another 4 RAM-chips on the motherboard. The motherboard being rev 6A, it supports a total of 1Mb ChipRAM, and having suitable RAM-chips, even an amateur like me could probably add another 512Kb to the motherboard.

Question is, what kind of RAM-chips would be suitable? Could I, for instance, take chips from a SIMM or EDO-stick, and if so - do they have to be the same size (i.e. 512kb/4)?

Which, in turn raise another question: The expansion-RAM for the A500. Is it possible to replace the RAM-chips the same way? From what I understand, the memory addressing is done by the machine itself, and for example for 2Mb-chips on such a board would theoretically mean the maximum of 8Mb FastRAM. Same question as before applies though, could such chips be salvaged from SIMM or EDO-sticks?

The only way to expand the RAM directly on mobo is taken RAM for an A501 with the same chips. SIMM chips are SMD, so is a no-no.

No equivalents for those, I'm afraid.

You also need a 1Mb capable Agnus. 2Mb Agnus are not pin-compatible, so you need a RAM expander.

And you need to modify the motherboard too in the case of 1Mb Agnus.

[Iznougoud]

And the same goes for expanding the A501 I suppose..?

[rkauer]

Originally Posted by Iznougoud

And the same goes for expanding the A501 I suppose..?

An A501 cannot be expanded in any way! Not enough address lines.

Yeah, I'm know about a trapdoor expansion who gives 2Mb to system, but connect to Gayle, too.

[Iznougoud]

Originally Posted by rkauer

An A501 cannot be expanded in any way! Not enough address lines.

It was just a thought anyway. Who knows, maybe I'll find that spare A501 that's lying around somewhere and have a go at the ChipRAM. Until then. Thanks for setting me straight on this.

[TheCorfiot]

Originally Posted by rkauer

An A501 cannot be expanded in any way! Not enough address lines.

Yeah, I'm know about a trapdoor expansion who gives 2Mb to system, but connect to Gayle, too.

Connects to Gary

[Iznougoud]

Leave Gary alone, you two! You hear me?!