Abstract

Thomas-Conrad commissioned The Tolly Group to evaluate the performance of its PCMCIA solution as part of Tolly's multi-vendor, industry study of LAN performance. Testing included both ODI and NDIS driver environments. 

Thomas-Conrad’s TC4141 PCMCIA Token Ring adapter is presented in this Tolly Technology Spotlight as part of the firm’s 1994 Industry Benchmark on PCMCIA LAN performance, focusing on how well mobile Token Ring adapters preserve desktop-class throughput in notebook environments. The report notes that PCMCIA LAN adapters were becoming increasingly important for mobile users and that, unlike traditional desktop cards, they had not yet been widely characterized with rigorous performance data. Tolly therefore evaluated the TC4141 in both Novell NetWare ODI and IBM LAN Server NDIS environments, using desktop ISA adapter performance as the baseline for comparison.  

In the ODI test suite, the TC4141 was measured across 64-, 256-, 512-, 1,024-, 2,048-, and 4,096-byte frame sizes, with packet burst disabled except at the maximum frame size where burst mode was enabled. At the largest 4,096-byte frame with packet burst enabled, the adapter’s throughput was within 16.4% of the desktop baseline. At the smaller tested frame sizes, throughput ranged from about 24% to 38% below baseline. The accompanying chart on page 1 shows, for example, 11.9Mbit/s for the desktop baseline versus 10.0Mbit/s for the TC4141 at 4,096-byte burst mode, and lower but still competitive results at smaller frames.  

In the NDIS suite, results were closer to baseline. Tests covered 81-, 256-, 512-, 1,024-, 2,048-, and 4,200-byte frames with packet burst enabled, and the report states that at the maximum 4,200-byte frame size the TC4141 performed 0.03% faster than the baseline ISA adapter. At all other frame sizes, throughput was within 8% to 19% of baseline, indicating that the PCMCIA form factor imposed only a modest penalty under the NDIS driver model.  

The test bed used a Toshiba T1910CS notebook as the mobile client, a 16Mbit/s Token Ring UTP MAU, a Compaq Deskpro server, NetWare 3.12 and IBM OS/2 LAN Server Advanced 3.0, plus protocol analyzers from Hewlett-Packard and Network General. Overall, the report concludes that the TC4141 delivered notebook Token Ring performance that approached high-performance ISA client adapters, especially under NDIS, making it a credible mobile LAN option for 16Mbit/s Token Ring environments.  

Thomas-Conrad was acquired by Compaq in 1995, after which the Thomas-Conrad name was dropped and its products and assets were absorbed into Compaq’s networking business.