How Cyberstorm Mk-II 040 and Warp Engine 4040 Boards Address RAM on Amiga 4000

[F_P_G_A]

Are there any advantages or disadvantages of having RAM on the A4000 mainboard or CyberStorm MK-II 040/Warp engine 4040 CPU boards?

Why Cstorm/Warp engine put the RAM on CPU board while there are RAM slots on mainboard?



Also where is the best place to discuss low-level hardware design aspects of Amiga 3000 and A4000?

[TribbleSmasher]

I am not an expert, but the motherboard RAM seems to be accessed with motherboard speed while the RAM on the CPU card might be driven by any speed the CPU on that card wants to, including bursts etc..
So the speed of the turbo card RAM is almost always faster by factors, hence the term 'turbo card'.

[F_P_G_A]

If one of these Turbo cards with on-board RAM installed on Amiga 4000 or 3000;  should the mainboard installed RAM to be removed?

[TribbleSmasher]

No, all RAM gets prioritised during bootup.
Faster RAM gets higher, slower gets lower priority.
Therefore it is perfectly fine to add e.g. 2 BigRAM256 or ZoRRAM to your Zorroslots even they are much slower than turbo card RAM.

[F_P_G_A]

How Amiga checks the presence of RAM?
For Turbo-Cards, add-on cards there is auto-config mechanism.

But for RAM? Does Amiga utilize ID ROMs on SIMMs?

[TribbleSmasher]

Any Autoconfig card that adds RAM follows AutoConfig, obviously. Otherwise the RAM has to be added to the system via different methods, like software ('addmem').
There is also a dedicated ROM routine that checks all memory address areas designated for, well, memory, aka RAM.
see
http://amigadev.elowar.com/read/ADCD_2.1/Hardware_Manual_guide/node00D3.html etc.

It is possible to add memory on a graphics card to be used as common RAM, but it will be slow, as it is not directly attached to the CPU bus, especially if a turbo card is used.

[F_P_G_A]

Tribblesmasher, first of all thanks a lot for answering my question..


About my last question; let's say we installed 1 SIMM or 2 SIMMS on A4000 mainboard.
How does it detect the presence and capacitiy of RAM slots on mainboard?

If we would have added RAM directly on CPU bus (like Warp Engine 4040)  is autoconfig mechanism used?

[TribbleSmasher]

I think the routines in ROM just poke around the address space in steps of 512kB and if the CPU does not throw a TRAP then there is some memory, i guess.