A4000 - should I use only CHIP RAM SIMM?

[Betelgeuse]

I have a couple of A4000s around and both of them have a CSMKII in them with loads of RAM. I think one of the Amigas, maybe both, have fully populated main board SIMM sockets. Should I remove those SIMMs and just leave the CHIP SIMM in or it makes no real difference in overall performance?

[alexh]

AFAIK the Amiga system has memory priorities. You can configure (or perhaps the drivers configure) priority. Putting accelerator fast memory over motherboard fast memory.

[BuzzBrain]

AFAIK the Amiga system has memory priorities. You can configure (or perhaps the drivers configure) priority. Putting accelerator fast memory over motherboard fast memory.

Are you sure about this?

I was told that the cyberstorm logic assigned the burst mode ram on the cyberstorm before the memory on the mainboard.

But I guess the memory timing/cycles for the cpu (040/060) would bee slower if you have simms in the mainboard.

I'm sure someone correct me, if this is total bull...

[alexh]

The CPU is not connected directly to the RAM. Not on the motherboard and not on an accelerator.

They are connected to a memory controller and not the same memory controller either. The Amiga motherboard has a DRAM controller called Ramsey and the accelerator has its own memory controller.

Accesses to particular addresses will have different timing. Accesses to motherboard fast RAM will typically be slower. However just having memory on the motherboard will not affect overall memory speed UNLESS it is being used.

But it wont normally be used because AFAIK on the Amiga memory is not in a general pool. Address ranges have priorities and accelerator memory will have a higher priority.

[Zac67]

Amiga memory nodes are prioritized, MEMF_FAST or MEMF_ANY will always get allocated from the fastest (=highest priority) pool.
So, slower mainboard RAM will not slow you down unless you run out of accelerator RAM - which would throw an error if mainboard RAM isn't available (MEMF_FAST) or would allocate even slower chipmem (MEMF_ANY).

[Matt_H]

This fine tool will report and allow you to change the memory priorities of different blocks of RAM.

On my 4000T, at least, the CSMK3/PPC RAM has the highest priority by default.