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Old 24 June 2013, 16:46   #27
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Join Date: Jul 2014
Location: Warsaw/Poland
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There are some myth around Falcon's memory bus (and Amiga also).

Originally Posted by kovacm View Post
3. Falcon with 16bit bus, 16MHz, and 4 cycles RAM access have 8MB/s BUT VIDEL also access to same RAM. In truecolor 320x200 mode it will take up to 13% of RAM time: so you will have around 7MB/s (more info:
not exactly true. Falcon's HiColor (16MHz pixelclock) mode needs 32MB/s bus bandwidth. From technical point of view Falcon has 8Mhz bus and Videl in order to minimize impact on CPU performance, gets data in 32bit chunks.

Regarding CPU, it has access to ST-RAM(chip-ram) every odd bus cycle. It means 4th CPU cycle access - 4Mhz. And It has Full Speed access to Fast-Ram.

Originally Posted by kovacm View Post
4. Not sure about A1200 chip RAM and Fast RAM speed... ?? can anyone give a info?
Below you can find memory peformance test A1200

  BusSpeedTest 0.19 (mlelstv)   Buffer:     262144 Bytes, Alignment: 32768
  memtype   addr       op         cycle     calib         bandwidth
  chip      $000B0000  readw    1052.4 ns   normal       1.9 * 10^6 byte/s
  chip      $000B0000  readl    1051.8 ns   normal       3.8 * 10^6 byte/s
  chip      $000B0000  readm    1052.2 ns   normal       3.8 * 10^6 byte/

And for Falcon:
    NemBench v2.1 - precision CPU/FPU profiler.

    Linear 32bit read (ST-Ram)   -> 5.475 MByte/sec (~103%)
    Linear 32bit write (ST-Ram)  -> 6.660 MByte/sec (~103%)
    Linear 32bit copy (ST-Ram)   -> 3.336 MByte/sec (~103%)
Therefore according to NemBench and BusSpeedTest, Falcon has better memory performance.
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