32-bit Fast RAM slower than 24-bit Fast on certain A1200 config

18 May 2013, 09:40

In the latest version, Z3 Fast RAM is caused to run at the same latency as Slow RAM. This occurs when selecting the cycle-exact A1200 configuration and starting the emulation without disabling 24-bit addressing first. Most of the hardware settings are set to the defaults with the exception of RAM, which was part of the issues occurring.

AIBB shows the ordinary Fast RAM operating at a latency index of 0.6. Slow indicates an index of 1.1. Z3 Fast takes on the latter index instead of the former if the emulator was configured as above. This can have a performance impact while Z3 RAM is enabled, because Autoconfig is giving it more priority than 24-bit Fast memory. The difference in performance is more noticeable if you have set the CPU speed to a higher than default value.

The best way to get around it is to disable 24-bit addressing before you start the emulation. Other than that, no other real problems.

Toni Wilen · 24 May 2013, 21:55

What is this "certain" A1200 config? (Note that I can't find anything that could explain this.)

18 May 2013, 09:40	#1
moshy Posts: n/a	32-bit Fast RAM slower than 24-bit Fast on certain A1200 config In the latest version, Z3 Fast RAM is caused to run at the same latency as Slow RAM. This occurs when selecting the cycle-exact A1200 configuration and starting the emulation without disabling 24-bit addressing first. Most of the hardware settings are set to the defaults with the exception of RAM, which was part of the issues occurring. AIBB shows the ordinary Fast RAM operating at a latency index of 0.6. Slow indicates an index of 1.1. Z3 Fast takes on the latter index instead of the former if the emulator was configured as above. This can have a performance impact while Z3 RAM is enabled, because Autoconfig is giving it more priority than 24-bit Fast memory. The difference in performance is more noticeable if you have set the CPU speed to a higher than default value. The best way to get around it is to disable 24-bit addressing before you start the emulation. Other than that, no other real problems.

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24 May 2013, 21:55	#2
Toni Wilen WinUAE developer Join Date: Aug 2001 Location: Hämeenlinna/Finland Age: 49 Posts: 26,505	What is this "certain" A1200 config? (Note that I can't find anything that could explain this.)

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