guides:virtual_modem:section_2
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guides:virtual_modem:section_2 [2025-02-24 19:58] omolini |
guides:virtual_modem:section_2 [2025-03-05 16:00] (current) omolini [Important note about USB-to-Serial adapters and pre-Pentium era computers] |
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| ===== Important note about USB-to-Serial adapters and pre-Pentium era computers ====== | ===== Important note about USB-to-Serial adapters and pre-Pentium era computers ====== | ||
| - | I have found in my testing, that the cheapest USB-to-serial adapters do not fare well with some older, pre-Pentium era computers with certain UART chips. The cheaper "molded blue plastic" USB-to-serial adapters would not work at all with a 386-class system with an **8250** UART, even at 9600 baud. However, it would work fine with my 486 system which had a **16550AF** UART running at 56 kbit/s. If you're unsure which UART chip you have, you can check it easily in DOS 6 by running the MSD tool. In the DOS prompt, type MSD to run the program, go to Com Ports (Press key C) and it will show the UARTs available. Commond UARTs are **8250, 16450 and 16550**. If you have a Pentium-class system, it is likely you have the best UART available. | + | I have found in my testing, that the cheapest USB-to-serial adapters do not fare well with some older, pre-Pentium era computers with certain UART chips. The cheaper "molded blue plastic" USB-to-serial adapters would not work at all with a 386-class system with an **8250** UART, even at 9600 baud. However, it would work fine with my 486 system which had a **16550AF** UART running at 56 kbit/s. If you're unsure which UART chip you have, you can check it easily in DOS 6 by running the MSD tool. In the DOS prompt, type MSD to run the program, go to Com Ports (Press key C) and it will show the UARTs available. Common UARTs are **8250, 16450 and 16550**. If you have a Pentium-class system, it is likely you have the best UART available. |
| If you are planning on using a 486 or older computer with either a **8250** or a **16450** UART, you can work around this limitation by using a genuine [[https://ebay.us/QnFezr|Prolific USB-to-Serial adapter]], or upgrade the computer by adding a serial I/O card with a **16550AF** UART chip. Please note that **8250** and **16450** UARTs will still be limited, and cannot handle much faster transfer speeds than about 9600 bit/s. To verify the chipset of your USB-to-serial adapter, plug in the adapter to a modern computer, open up Device Manager. Under "Ports" you will see the Prolific adapter identify as "Prolific USB-to-Serial Comm Port". | If you are planning on using a 486 or older computer with either a **8250** or a **16450** UART, you can work around this limitation by using a genuine [[https://ebay.us/QnFezr|Prolific USB-to-Serial adapter]], or upgrade the computer by adding a serial I/O card with a **16550AF** UART chip. Please note that **8250** and **16450** UARTs will still be limited, and cannot handle much faster transfer speeds than about 9600 bit/s. To verify the chipset of your USB-to-serial adapter, plug in the adapter to a modern computer, open up Device Manager. Under "Ports" you will see the Prolific adapter identify as "Prolific USB-to-Serial Comm Port". | ||
guides/virtual_modem/section_2.txt · Last modified: 2025-03-05 16:00 by omolini
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