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Another Blerb! youtu.be/3W5ydPuqpTg I purchased one of these unbranded CH375 8-bit ISA USB interface cards a while back and it finally arrived. So let's test it out with MS-DOS on an IBM PC AT 5170 and try it with a USB flash drive and some DOS games!

5:25 PM · Apr 12, 2022

Replying to

So, fun fact: This board is basically just a CH375 chip with a tiny bit of ISA glue logic. That chip is from WCH: Nanjing Qinheng Microelectronics. (I assume that acronym makes more sense in Chinese) They make a TON of little weird chips to do things like this

and apparently the trick is that they're really just shipping one chip: it's a modified 8051 core with some PROM on it.

so they just write different code for their generic microcontroller and then ship it as a simple chip that does one thing. You can avoid all the complexity of talking whatever specific protocol it does, because they already programmed it and exposed a simple interface to it

So the CH375 is a specialized version of a CH374 which is a generic USB interface chip. Basically the CH375 just does USB filesystem access.

also fun fact: I think this device exists as a clone of a retro hobbist device, the Lo-tech ISA USB Adapter: lo-tech.co.uk/wiki/Lo-tech_I

So they have plenty of other chips that you might could build a board like this for. Like the CH9350, which is a host device for USB keyboard/mice.

correction: CH376 is the USB-filesystem version of the CH374/375. If this uses a real 375, it could do all sorts of USB-host functionality, it just needs new BIOS or drivers.

USB flash drives on 8-bit ISA bus using CH375 ISA to USB adapter

also, there's no limitation of 512mb (as seen in the video) in the CH375 firmware, that I can see. So presumably that's just a limitation in the BIOS or driver. It could be fixed!

And

found this blogpost which looks into some of that:

toughdev.com

I purchased the CH375 ISA to USB adapter from Taobao, hoping for an easier way to transfer files to my…

also, interestingly: the CD shown in LGR's video seems to have some source code on it. I'm not sure if that's for the DOS driver, the BIOS, or something else entirely. Might be useful to archive it,

BTW I played around with a small dev board for the CH376S (which is specialized for USB disks), mainly to see if it supports floppy drives. Nope.

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