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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: derringer3 on November 05, 2006, 02:04:16 PM
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I search for some docs recently, but i dont't find any. So is there any hardware faq/doc which is unrevail the amiga's hardware speed/transfer rates?
For example: the zorro III max bandwith in MB/s, or what is the a500 bus speed max transfer rate. Are there any doc which is tell how fast is the custom chip in MHz or speed?
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Pretty simple:
- OCS/ECS machines run on a bus frequency of 7.16 Mhz, bus width is 16 bit, including Zorro II. The 68000 can use every other cycle to access the bus, so that's 7 MB/s.
- Turboboards have their own (fastmem) bus, so bandwidth varies.
- The A3k's chipmem can be accessed in 32 bit cycles (only) by the CPU, so that doubles bandwidth.
- AGA machines have 4x the bandwidth (double clock rate and 32 bit access)
- AGA blitters can operate in 16 bit only
- Zorro III is an asynchronous bus, so it's not possible to give a specific bandwidth. In A3k/A4k it maxes at ~20 MB/s (AFAIK).
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The 68000 can use every other cycle to access the bus, so that's 7 MB/s.
There's 7MB/S total to/from chipmem. The 68000 gets half of that at best, same with ROM and zorroII bus.
AGA machines have 4x the bandwidth (double clock rate and 32 bit access)
The memory bus isn't really double the clock rate, but there is 4x bandwidth (for the display, not for the CPU) because the chipset can do two reads in one turn with 64-bit aligned data.
Zorro III ...
It's 32-bit and 25MHz and should be able to go 80MB/S using burst mode although in practice it is more like 20MB/S as you say.