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harbaum / NanoMig

Amiga Minimig ported to the Tang Nano 20k FPGA
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graphics corrupted with more than 512k chipmem #3

Open mibosshard opened 3 weeks ago

mibosshard commented 3 weeks ago

tested with Kickstart 1.3 and 2.05: as soon as more than 512k of chipmem is activated, graphics glitches appear (e.g. when resizing or moving windows in Workbench) or the system hangs (e.g. running boing-ball demo).

running NanoMig with 512k of chipmem only, the system seems to be rock solid, AFAICT.

harbaum commented 3 weeks ago

The whole system is unstable and many games and demos don't run properly. This is well-known.

harbaum commented 1 week ago

I've had a closer look at the ram timing and I'd say that the CPU can access ram pretty reliably. Also ram test software detects no ram problems.

I assume it's one of the dma units that has problems accessing the ram. This may also explain other graphical glitches I see in demos.

I am no Amiga user. But I think I've read somewhere that the decoding of mfm floppy data is done by the blitter. That could also explain why floppy I/o seems to have issues as the blitter imho also uses dma.

But as I said, I basically know nothing about amigas ...

darius600 commented 1 week ago

What I read Blitter can be used for MFM decoding: https://en.wikipedia.org/wiki/Amiga_Original_Chip_Set#Floppy_disk_controller Or it can also be done with CPU only. Here 2 Trackloaders without Blitter: https://github.com/deplinenoise/trackloader/blob/master/bootblock.asm https://github.com/AxisOxy/Planet-Rocklobster/blob/master/demo/framework/loader.asm

What I see Blitter.v in Nanomig is (almost) identical with Blitter.v in minimig-de1: https://github.com/rkrajnc/minimig-de1/blob/master/rtl/minimig/Blitter.v (master) https://github.com/rkrajnc/minimig-de1/blob/4677847cfe7b7cb28066d980d687b2c158d037ab/rtl/minimig/Blitter.v (the rel 4 I am using, which is working fine)