Macintosh Serial Throughput: Modem Results

1998 – Your results may vary, but this should provide a good starting point for tweaking serial throughput on your Mac setup. Note that FreePPP allows serial port settings of 115.2 kbps and 230.4 kbps, settings not possible with Apple’s serial toolbox routines. This follows up on our earlier article, Macintosh Serial Throughput, providing real world results.

For the best possible serial throughput, don’t use your floppy drive, run CPU-intensive programs, or transfer data over LocalTalk – and minimize use of your hard drive.

Low End Mac readers were asked to indicate their Mac model, accelerator (if present), Mac OS version, PPP software used, kind of networking (classic or Open Transport), modem used, reported connection speed from ISP, DTE rate (serial port speed), maximum reported throughput, and level of packet loss (none, low, high). Most users did not report full information.

68000-based Macs

Plus (8 MHz), reported by Rowland

  • 28.8kbps, some packet loss, best overall throughput
  • 19.2kbps, no packet loss, slightly lower throughput
  • packet loss at 57.6 kbps made throughput slower than at 9600bps

Plus (8 MHz, System 7.5.3), reported by Mike Friese

  • packet loss due to overruns, CRC errors beyond 19.2kbps

68020-based Macs

No reports

68030-based Macs

IIci (25 MHz), reported by Dirk von Seggern

  • 115.2kbps with few dropped packets using V.34+ modem
  • 64kbps throughput with ISDN at 115.2kbps

LC III (25 MHz)

  • 115.2kbps, unknown packet loss

Perfoma 460 (33 MHz), reported by Daryl Mitchell

  • 115.2kbps “works great” with 33.6 v.42bis modem

68040-based Macs

Centris 610 (20 MHz), System 7.5.5, FreePPP, OT 1.1.2, Supra 56e modem, reported by Dan Knight

  • 230.4kbps, one dropped packet, 88.4kbps throughput on statistics page for my ISP
  • 115.2kbps, no dropped packets, 83.2kbps throughput
  • 57.6 kbps, no dropped packets, 48.7kbps

Performa 475 (25 MHz), System 7.1 and 7.6, reported by Rowland

  • 115.2kbps

Centris 660av (25 MHz), System 7.5.5, FreePPP, OT 1.1.2, Supra 56e modem, 42-44kbps connection, reported by Dan Knight

  • 230.4kbps, few dropped packets, 88.5kbps throughput on statistics page for my ISP
  • 115.2kbps, no packet loss, 81.6kbps throughput
  • 57.6 kbps, no packet loss, 52.7kbps throughput

Quadra 650 (33 MHz), System 8.0, reported by Jonathan Ploudre

  • 230.4kbps, few dropped packets, 90kbps maximum throughput
  • 115.2kbps, no packet loss, 90kbps maximum throughput
  • 57.6 kbps, no packet loss, 49kbps maximum throughput
  • Gained 10-15% on sustained throughput by moving from 57.6 kbps to 115.2kbps.


  • Mac Plus works best with serial port set to 19.2kbps or 28.8kbps – newer 68000-based Macs may do better
  • 68030-based Macs tend to work very well at 115.2kbps
  • 68040-based Macs are generally a bit faster at 230.4kbps than at 115.2kbps

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