bustest is a small utility to measure data transfer speed
to and from memory. It requires AmigaOS2.0 or higher.

Method:

  determine a chunk of memory and time read and write operations with the
  pretty exact CIA timers. After that the overhead of the measurement is
  compensated.

  During measurement other tasks are locked out, but _interrupts_ are not.
  However, interrupt activity shouldn't influence the measurement unless
  you send lots of data to the serial port or sit on a heavy duty network.

What you get ?

  The performance of a very large sequence of MOVE instructions.
  Either word or long word moves or bursts of 8 longword moves
  using the MOVEM instruction are used.

Caveats:

  The 68040 and 68060 usually uses a _copyback_ cache. This means,
  that _writing_ causes the cache to _read_ the data first (and
  later _write_ it) thus halving write performance when writing
  large blocks.

  Small blocks like local variables usually fit into the cache and
  are just read once which is the reason for the good performance
  of the copyback cache. But.. block writes are the worst case. The
  68040 has a special MOVE16 instruction to circumvent that problem,
  but it is not used in the AmigaOS (nor in this test program).

  The 68040 and 68060 have rather large caches and especially the
  68060 uses an effective pseudo-random cache replacement strategy
  which bias results if the tested memory area isn't much larger
  than the cache. This is the reason why previous versions of bustest
  yielded too high transfer rates for cached memory. The 16k area
  still generated more than 50% cache hits in case of the 68060.

How to use:

  bustest ADDR/K,SIZE/K,CHIP/S,FAST/S,ROM/S,MEGA/S

  ADDR/K   hexadecimal start address of a memory region to test.
           This address can specify memory that does not appear in
           the system memory list (like a graphics frame buffer)
           or memory in the free list. bustest tries to check the
           address and will refuse to test it when it believes that
           the memory is used by anything else. BUT: it is possible
           to specify addresses that are not mapped to anything,
           resulting in thousands of bus errors. So be careful when
           using that option.
  SIZE/K   size of the test region in bytes. You can use the suffix
           'k' to specify units of 2^10 bytes and 'm' to specify
           units of 2^20 bytes. The size is rounded up to a multiple
           of 128 which is the granularity of the test loop. The
           default is 256 kilobytes.
  CHIP/S   test an AllocMem'd region in chip memory.
  FAST/S   test an AllocMem'd region in fast memory.
  ROM/S    test the region starting at address $00F80000, i.e the
           kickstart ROM (or the RAM that is mapped there with the
           MMU if you use something like CPU FASTROM).
  MEGA/S   show data rates in units of 2^20Byte/s instead of the
           normal 10^6Byte/s.

Examples:

  this test was done on an A3000 with a CyberStorm Mk2 accelerator board.
  the ROM is actually a copy of the Kickstart in RAM remapped with the
  rom2fast program.

  1> bustest fast chip rom
  BusSpeedTest 0.19 (mlelstv)   Buffer:     262144 Bytes, Alignment: 32768
  ========================================================================
  memtype   addr       op         cycle     calib         bandwidth
  fast      $086F8000  readw      71.5 ns   normal      28.0 * 10^6 byte/s
  fast      $086F8000  readl     121.7 ns   normal      32.9 * 10^6 byte/s
  fast      $086F8000  readm     121.4 ns   normal      33.0 * 10^6 byte/s
  fast      $086F8000  writew     86.9 ns   normal      23.0 * 10^6 byte/s
  fast      $086F8000  writel    174.7 ns   normal      22.9 * 10^6 byte/s
  fast      $086F8000  writem    174.3 ns   normal      22.9 * 10^6 byte/s
  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/s
  chip      $000B0000  writew    568.4 ns   normal       3.5 * 10^6 byte/s
  chip      $000B0000  writel    569.0 ns   normal       7.0 * 10^6 byte/s
  chip      $000B0000  writem    569.0 ns   normal       7.0 * 10^6 byte/s
  rom       $00F80000  readw      71.5 ns   normal      28.0 * 10^6 byte/s
  rom       $00F80000  readl     122.6 ns   normal      32.6 * 10^6 byte/s
  rom       $00F80000  readm     121.9 ns   normal      32.8 * 10^6 byte/s

  If you reduce the test area you see the speed of the cache. The
  68060 can access the cache at every clock for a maximum speed of
  50MHz * 4Byte = 200MByte/s.

  1> bustest fast size=2k
  BusSpeedTest 0.19 (mlelstv)   Buffer:       2048 Bytes, Alignment: 32768
  ========================================================================
  memtype   addr       op         cycle     calib         bandwidth
  fast      $08640000  readw      20.2 ns   normal      98.9 * 10^6 byte/s
  fast      $08640000  readl      20.1 ns   normal     198.7 * 10^6 byte/s
  fast      $08640000  readm      20.1 ns   normal     199.0 * 10^6 byte/s
  fast      $08640000  writew     20.0 ns   normal     100.1 * 10^6 byte/s
  fast      $08640000  writel     20.1 ns   normal     198.7 * 10^6 byte/s
  fast      $08640000  writem     20.1 ns   normal     198.7 * 10^6 byte/s

  If you increase the size you see partial cache trashing caused by
  interrupts that reduce the effective bandwidth. Also, in this case
  bustest cannot effectively compensate overhead but shows a less
  precise estimate (calib == "biased")
  
  1> bustest fast size=8k
  BusSpeedTest 0.19 (mlelstv)   Buffer:       8192 Bytes, Alignment: 32768
  ========================================================================
  memtype   addr       op         cycle     calib         bandwidth
  fast      $08640000  readw      20.7 ns   biased      96.6 * 10^6 byte/s
  fast      $08640000  readl      21.3 ns   biased     188.2 * 10^6 byte/s
  fast      $08640000  readm      21.7 ns   biased     184.6 * 10^6 byte/s
  fast      $08640000  writew     20.9 ns   biased      95.6 * 10^6 byte/s
  fast      $08640000  writel     21.3 ns   biased     187.4 * 10^6 byte/s
  fast      $08640000  writem     21.9 ns   biased     182.3 * 10^6 byte/s

  If you increase the size further the cache becomes less effective.
  Here is the result that compares to the old bustest (version 0.07):

  1> bustest fast size=16k
  BusSpeedTest 0.19 (mlelstv)   Buffer:      16384 Bytes, Alignment: 32768
  ========================================================================
  memtype   addr       op         cycle     calib         bandwidth
  fast      $08640000  readw      54.2 ns   biased      36.9 * 10^6 byte/s
  fast      $08640000  readl      87.2 ns   biased      45.9 * 10^6 byte/s
  fast      $08640000  readm      88.5 ns   biased      45.2 * 10^6 byte/s
  fast      $08640000  writew     64.8 ns   biased      30.9 * 10^6 byte/s
  fast      $08640000  writel    122.8 ns   biased      32.6 * 10^6 byte/s
  fast      $08640000  writem    124.9 ns   biased      32.0 * 10^6 byte/s

  Here is the result for a test of the motherboard memory (specifying
  FAST did AllocMem() the test area and the SIMMs on the CyberStorm
  have a higher priority).
  
  1> bustest addr=07010000
  BusSpeedTest 0.19 (mlelstv)   Buffer:     262144 Bytes, Alignment: 32768
  ========================================================================
  memtype   addr       op         cycle     calib         bandwidth
  user      $07010000  readw     159.3 ns   normal      12.6 * 10^6 byte/s
  user      $07010000  readl     299.0 ns   normal      13.4 * 10^6 byte/s
  user      $07010000  readm     298.8 ns   normal      13.4 * 10^6 byte/s
  user      $07010000  writew    254.5 ns   normal       7.9 * 10^6 byte/s
  user      $07010000  writel    511.8 ns   normal       7.8 * 10^6 byte/s
  user      $07010000  writem    507.5 ns   normal       7.9 * 10^6 byte/s

  This test couldn't start at $07000000 because the first few bytes
  are used up by the memory header. If you try you just get an error
  message:

  1> bustest addr=07000000
  Address $07000000 is mapped. Test aborted.

Problems:

  Blitter activity can produce pretty bogus results.
  The test takes more time than the one in bustest 0.07 because of
  the larger test area

Michael van Elst

 PERMSSN    UID  GID    PACKED    SIZE  RATIO     CRC       STAMP          NAME
---------- ----------- ------- ------- ------ ---------- ------------ -------------
[generic]                 5983   11544  51.8% -lh5- 5adc Jan 21  1997 bustest
[generic]                 2672    8548  31.3% -lh5- d307 Jan 21  1997 bustest.readme
---------- ----------- ------- ------- ------ ---------- ------------ -------------
 Total         2 files    8655   20092  43.1%            Jan 24  1997