(AI Generated Content - I have verified that it works)

Using a USB Thumb Drive with the Pocket8086 (DOS/Windows 3.0)

The Pocket8086 includes a CH375B USB controller for “U-disk” support, but the default DOS driver often fails with modern flash drives. Symptoms include the system hanging on boot if a USB stick is inserted, or “Not ready reading drive D” errors when trying to access the drive[[1]](https://forum.vcfed.org/index.php?threads/book-8088-discovery-and-modification-thread.1245155/page-30#:~:text=I%20have%20a%20Pocket%208086%2C,hangs%20for%20a%20long%20time)[[2]](https://www.vogons.org/viewtopic.php?t=101513#:~:text=I%20have%20a%20512%20mb%2C,anyone%20have%20suggestions%3F%20Thank%20you). The solution is to update the DOS USB storage driver and ensure the flash drive is formatted correctly. Follow these steps to get your USB thumb drive working:

Use a Compatible FAT16 Format on the USB Drive: Make sure the thumb drive is formatted as a single FAT16 partition (DOS 6.22 can’t read FAT32/exFAT). Use a capacity of 2 GB or less, since classic DOS has a ~2 GB FAT16 limit[[3]](https://voidstar.blog/2025/03/18/usb-on-x86-isa-8-bit/#:~:text=Formatting%20the%20USB). (For example, a 1 GB FAT16 partition is fine.) Avoid multiple partitions or sizes above 2 GB – older CH375 drivers would freeze if the drive was over 512 MB or not FAT16[[4]](https://www.toughdev.com/content/2018/04/usb-flash-drives-on-8-bit-isa-bus-using-ch375-isb-to-usb-adapter/#:~:text=USB%20flash%20drives%20on%208,FAT16%2C%20or%20contains%20multiple). You’ve already formatted the 1 GB stick as FAT16, which is appropriate.
Download the Updated CH375 DOS Driver: Acquire FreddyV’s CH375 v0.22 optimized driver for DOS. This driver replaces the original “CH375DOS.SYS v2.0a” driver, which is known to be incompatible with many flash drives[[5]](https://yeokhengmeng.com/2023/06/teardown-and-review-of-hand386/#:~:text=,the%20Youtuber%20THE%20PHINTAGE%20COLLECTOR). The updated driver greatly improves compatibility and speed (3×–5× faster transfers)[[6]](https://vogonsdrivers.com/getfile.php?fileid=1991&menustate=0#:~:text=Description%20CH375%20New%20Driver%20by,22). You can find it on the VOGONS vintage driver library (file ch375v022.zip)[[7]](https://forum.vcfed.org/index.php?threads/book-8088-discovery-and-modification-thread.1245155/#:~:text=Freddy%20V%20created%20an%20improved,php%3Ffileid%3D1991%26menustate%3D0). Download that ZIP on your Linux PC and extract it.
Transfer the Driver to the Pocket8086: You’ll need to get the new .SYS driver file onto the Pocket8086’s CF card (since USB isn’t working yet). Here are two methods:
Method A: CF Card Sneakernet – Power off the Pocket8086 and remove the CF card (the 512 MB card containing DOS). Using a CF-to-USB adapter or card reader on your Linux machine, mount the CF card. Copy the new driver file onto the CF (for example, into C:\DOS or a new C:\DRIVERS directory). Safely eject the CF and reinsert it into the Pocket8086. (Tip: The CF slot might be snug – using a small tab or tape on the card can help pull it out, as some users suggest[[8]](https://yeokhengmeng.com/2023/06/teardown-and-review-of-hand386/#:~:text=,the%20Youtuber%20THE%20PHINTAGE%20COLLECTOR).)
Method B: Serial XMODEM Transfer – If you can’t easily use a CF reader, you can send the file over the serial link using a terminal program with XMODEM (since Windows 3.0 includes a Terminal app that supports XMODEM). Connect the Pocket8086 to your Linux PC via the serial cable. On the Pocket8086, launch Terminal (in Windows 3.0) and configure it for the correct COM port (likely COM1) at an appropriate baud rate (e.g. 9600 bps to start). In Terminal, initiate an XMODEM receive (you may find this under a Transfer menu or by pressing the receive button and selecting XMODEM). On the Linux side, use a terminal program (e.g. minicom) or the sx command (from the lrzsz package) to send the driver file with XMODEM protocol. The Windows 3.0 Terminal will receive the file and save it (you’ll be prompted to name the file; match the original name, e.g. CH375V86.SYS). After transfer, verify the file is on the Pocket8086 (e.g. by listing the directory in DOS).
Update CONFIG.SYS to Load the New Driver: Reboot the Pocket8086 into DOS (or exit to DOS from Windows), and open the C:\CONFIG.SYS file for editing (you can use the DOS EDIT command or Windows Notepad). Locate the line that loads the old USB driver (likely something like DEVICE=C:...\CH375DOS.SYS ...). Disable that line by putting REM at the start or deleting it. Now add a new line to load the updated driver. Use the same I/O port and parameters as the old line. For the Pocket8086, the CH375 is usually at port 260h with no IRQ. For example:

DEVICE=C:\DOS\CH375V86.SYS @260 %2

Ensure the path points to where you put the new .SYS file. Here, @260 sets the I/O address 0x260, and %2 is a speed/delay parameter (the original driver used a value like 02h for I/O speed). If your CONFIG.SYS had a different % value, use that. (The %2 is often safe for an 4.77–10 MHz XT-class system; it adds a slight I/O delay. %0 means no added delay – you can try %0 as well if you want maximum speed and the system is stable[[9]](http://www.vogons.org/viewtopic.php?t=43311&start=160#:~:text=Add%20a%20line%20in%20the,SYS).) Note: If your Pocket8086 is using an NEC V30 CPU, use the driver optimized for 8086-class CPUs. In the v0.22 driver pack, this file may be named CH375286.SYS (as referenced above) or CH375V86.SYS – AUTHORS NOTE: I had to use the V86 version. 286 would freeze on write. If your unit were running an 8-bit 8088 processor (less common for the Pocket8086), you’d instead use the CH375V88.SYS driver optimized for 8088/XT[[10]](https://forum.vcfed.org/index.php?threads/book-8088-discovery-and-modification-thread.1245155/page-30#:~:text=,8086%20%2F%2016Bit%20memory%20BUS). (In summary, “286” or “V86” driver = for 8086/V30, and “V88” = for 8088.) Once you’ve added the new DEVICE line, save CONFIG.SYS and reboot the Pocket8086.

1. Reboot and Test the USB Drive: After reboot, DOS will load the new CH375 driver. If you boot with the USB thumb drive already plugged in, the driver should detect it during startup and assign it as drive D: (you should see a message like “add disk D:” on the DOS boot screen). If the system still pauses too long at startup, simply boot without the USB inserted, then plug it in at the DOS prompt. In DOS, type D: and press Enter – it should switch to the D: drive without errors, allowing you to dir or access files on the USB. In Windows 3.0’s File Manager, you can now open the D: drive and browse the contents normally. The updated driver is much more stable, so the file explorer should no longer hang indefinitely[[5]](https://yeokhengmeng.com/2023/06/teardown-and-review-of-hand386/#:~:text=,the%20Youtuber%20THE%20PHINTAGE%20COLLECTOR). According to the Pocket8086 manual, once the driver is working “the assigned disk symbol, such as 'D', will appear” for the USB device, and you can simply enter D: to access it[[11]](https://www.8086cpu.com/static/upload/file/20240612/1718191966511824.pdf#:~:text=The%20CH375B%20USB%20controller%20integrates,navigate%20to%20the%20D%20drive).

Troubleshooting Tips: If D: still doesn’t appear or remain accessible, double-check that the thumb drive is partitioned/formatted in FAT16 (use a smaller size drive if necessary) and that CONFIG.SYS is loading the correct driver file. Also, some users found the CH375 driver may initialize more reliably at the original 4.77 MHz CPU speed. If your Pocket8086 is in “Turbo” mode (10 MHz) by default, try toggling turbo off for boot-up. For example, press the Turbo function key to slow down to 4.77 MHz before or during boot (on some units Fn+6 toggles the turbo mode). Once DOS finishes loading the driver at the slower speed, you can re-enable turbo. One Pocket8086 owner reported that disabling turbo at boot let the driver load properly, after which the USB drive worked and turbo could be turned back on[[12]](https://forum.vcfed.org/index.php?threads/book-8088-discovery-and-modification-thread.1245155/page-30#:~:text=I%20was%20able%20to%20get,the%20boot%20with%20turbo%20on). This may or may not be needed, but it’s worth a try if you still encounter issues. Finally, if possible test with a different flash drive – while the new driver is far more compatible, extremely large or unusual USB sticks might still pose problems. A standard small-capacity drive (512 MB–2 GB, FAT16) is ideal[[3]](https://voidstar.blog/2025/03/18/usb-on-x86-isa-8-bit/#:~:text=Formatting%20the%20USB).

By updating the driver and following the above steps, your Pocket8086 should now recognize and use USB thumb drives as the D: drive in DOS/Windows 3.0, without stalling or errors. This updated setup has been verified by the community to resolve the “drive not ready” problems and improve overall USB storage support on these retro machines[[9]](http://www.vogons.org/viewtopic.php?t=43311&start=160#:~:text=Add%20a%20line%20in%20the,SYS)[[5]](https://yeokhengmeng.com/2023/06/teardown-and-review-of-hand386/#:~:text=,the%20Youtuber%20THE%20PHINTAGE%20COLLECTOR). Enjoy transferring files to your Pocket8086 via USB!

Sources:

· Pocket8086 user discussions – resolving “Drive D: not ready” errors by replacing the CH375DOS driver[[2]](https://www.vogons.org/viewtopic.php?t=101513#:~:text=I%20have%20a%20512%20mb%2C,anyone%20have%20suggestions%3F%20Thank%20you)[[9]](http://www.vogons.org/viewtopic.php?t=43311&start=160#:~:text=Add%20a%20line%20in%20the,SYS)

· Pocket8086/Book8088 community advice on CH375B USB driver upgrades (FreddyV’s optimized driver v0.22)[[7]](https://forum.vcfed.org/index.php?threads/book-8088-discovery-and-modification-thread.1245155/#:~:text=Freddy%20V%20created%20an%20improved,php%3Ffileid%3D1991%26menustate%3D0)[[5]](https://yeokhengmeng.com/2023/06/teardown-and-review-of-hand386/#:~:text=,the%20Youtuber%20THE%20PHINTAGE%20COLLECTOR)

· Voidstar blog – notes on CH375 DOS driver limitations (FAT16, size limits)[[3]](https://voidstar.blog/2025/03/18/usb-on-x86-isa-8-bit/#:~:text=Formatting%20the%20USB)[[4]](https://www.toughdev.com/content/2018/04/usb-flash-drives-on-8-bit-isa-bus-using-ch375-isb-to-usb-adapter/#:~:text=USB%20flash%20drives%20on%208,FAT16%2C%20or%20contains%20multiple)

· Pocket8086 User’s Guide – usage of the USB port under DOS (drive appears as “D:” when a USB stick is connected)[[11]](https://www.8086cpu.com/static/upload/file/20240612/1718191966511824.pdf#:~:text=The%20CH375B%20USB%20controller%20integrates,navigate%20to%20the%20D%20drive)

[[1]](https://forum.vcfed.org/index.php?threads/book-8088-discovery-and-modification-thread.1245155/page-30#:~:text=I%20have%20a%20Pocket%208086%2C,hangs%20for%20a%20long%20time) [[10]](https://forum.vcfed.org/index.php?threads/book-8088-discovery-and-modification-thread.1245155/page-30#:~:text=,8086%20%2F%2016Bit%20memory%20BUS) [[12]](https://forum.vcfed.org/index.php?threads/book-8088-discovery-and-modification-thread.1245155/page-30#:~:text=I%20was%20able%20to%20get,the%20boot%20with%20turbo%20on) Book 8088 discovery and modification thread | Page 30 | Vintage Computer Federation Forums

https://forum.vcfed.org/index.php?threads/book-8088-discovery-and-modification-thread.1245155/page-30

[[2]](https://www.vogons.org/viewtopic.php?t=101513#:~:text=I%20have%20a%20512%20mb%2C,anyone%20have%20suggestions%3F%20Thank%20you) Pocket 8086 - How to get a USB drive to work? \ VOGONS

https://www.vogons.org/viewtopic.php?t=101513

[[3]](https://voidstar.blog/2025/03/18/usb-on-x86-isa-8-bit/#:~:text=Formatting%20the%20USB) USB on x86 ISA (8-bit) — voidstar

https://voidstar.blog/2025/03/18/usb-on-x86-isa-8-bit/

[[4]](https://www.toughdev.com/content/2018/04/usb-flash-drives-on-8-bit-isa-bus-using-ch375-isb-to-usb-adapter/#:~:text=USB%20flash%20drives%20on%208,FAT16%2C%20or%20contains%20multiple) USB flash drives on 8-bit ISA bus using CH375 ISA to USB adapter