1MB Chip / 0.5M+0.5M in Adv.Chipset

[amilo3438]

There is an option in Adv.Chipset 1MB Chip / 0.5M+0.5M introduced from WinUAE 3.0.0.

I guess it function is to enable 1MB Chip RAM made of two 512KB chips in configurations with A500 ECS chipset.

So I run winuae with qs A500 ECS 512 chip + 512 slow config with 1MB Chip / 0.5M+0.5M enabled in Adv.Chipset and check in AmigaTestKit, Sysinfo and WB avail to see if reports 1MB chip ram, hmm but it does not.

Am I doing something wrong or something is broken?


EDIT: If run qs A1200 basic configuration I noticed the 1MB Chip / 0.5M+0.5M is already selected in the Adv.Chipset and not possible to disable!? (what is the function of this option?)

EDIT2: Seems if Chip memory is >512 than this function is enabled! (but if enable this function alone it does not change the Chip memory)

[Waccoon]

This mimics the functionality of the 1MB jumper on the A500 motherboard and controls how memory is mirrored in the chip RAM address space.

If it's set and you have less than 1MB of chip RAM selected, any unpopulated space in the first 1MB of memory will just be floating noise. If it's not set, then unpopulated space will be mirrors of however much memory there is.

Whether memory in the upper 512K bank is mirrored or not may affect the compatibility of some software that probes memory directly to see if anything is there. On real hardware, there is an additional EXRAM signal that controls the visibility of slow RAM, which works in tandem with the 1MB jumper setting.

[ross]

Originally Posted by amilo3438

So I run winuae with qs A500 ECS 512 chip + 512 slow config with 1MB Chip / 0.5M+0.5M enabled in Adv.Chipset ..

The difference is in 'who' is seeing the RAM:
for the CPU a normal slow-ram card is at $c00000 location, for Agnus is a plain 1MB of RAM.

Basically only a blitter test could discover this configuration, with the CPU it is impossible.

[amilo3438]

Thanks to both of you for the clarification.

I had just finished testing on my real one A500 rev.6 (512 chip + 512 slow) with monitor program to check mirroring locations $80000 with $00000, and yes, they are exactly the same.
I knew about it but I had obviously forgotten (it must comes with age).

Btw.
Regarding my actual A500, it seems to still work properly (the last check was about 10 years ago) except maybe here and there when I insert the floppy it says it is not inserted.
Also, I noticed that Workbench recognize the clock first time I booted but second time it reported (unset) (unset) (unset)! (so will have to check what is happening there one day)
Must say that I still prefer winuae emulation over a real thing -> much more comfortable to work with and not so different.