deanimator
Experienced Member
Hi everyone,
does anyone know why an A500 with a 1MB-capable "Fat Agnus" (CSG 8372A) cannot actually address full 1MB (1024K) of RAM ?
It seems to be around 6 kilobytes short, reporting in SysInfo as a 1018K total, with an upper address bound of $000fe7ff. In the Workbench CLI, "avail" returns yet an interesting value of 1040152 bytes total RAM. Who's telling the truth now, toss a coin
I have verified both behaviors on my Rev6 A500 and also on the WinUAE emulator, attempting to rule out chipset issues. Also when the RAM upgrade is set as slow RAM, then there's 512K of chip and 506K of slow RAM reported by SysInfo 4.4 on both real hardware and the emulator; 1018K in total.
It's not that I would care about a couple of missing K's in the year of our lord 2023, but this in turn leads to issues for software requiring at least a proper 1MB of chip RAM, as in an A500+ or A1200. Think Worms/FLT (crashes after intro) and OTT (left channel samples sound corrupt). Out of curiosity, what happens with the last 6K - anyone knows, or is it an issue of the "Fat Agnus" addressing chip?
Regards
does anyone know why an A500 with a 1MB-capable "Fat Agnus" (CSG 8372A) cannot actually address full 1MB (1024K) of RAM ?
It seems to be around 6 kilobytes short, reporting in SysInfo as a 1018K total, with an upper address bound of $000fe7ff. In the Workbench CLI, "avail" returns yet an interesting value of 1040152 bytes total RAM. Who's telling the truth now, toss a coin

I have verified both behaviors on my Rev6 A500 and also on the WinUAE emulator, attempting to rule out chipset issues. Also when the RAM upgrade is set as slow RAM, then there's 512K of chip and 506K of slow RAM reported by SysInfo 4.4 on both real hardware and the emulator; 1018K in total.
It's not that I would care about a couple of missing K's in the year of our lord 2023, but this in turn leads to issues for software requiring at least a proper 1MB of chip RAM, as in an A500+ or A1200. Think Worms/FLT (crashes after intro) and OTT (left channel samples sound corrupt). Out of curiosity, what happens with the last 6K - anyone knows, or is it an issue of the "Fat Agnus" addressing chip?
Regards