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Macintosh Serial Throughput: Results

Your results may vary, but this should provide a good starting point for tweaking serial throughput on your setup. Note that FreePPP allows serial port settings of 115.2kbps and 230.4kbps, settings not possible with Apple's serial toolbox routines. If you have different results, I'd very much like to publish them here.

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

In email Dan Knight reporting your results, please indicate your computer model, accelerator (if present), system version, PPP software used, 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).

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

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.

Other Resources

Modem performance using FreePPP and OT PPP on at 5320, Adrian Winnard

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