low latency ps/2 to usb adapter?

[vibe]

Sadly I must switch my favorite keyboards from ps/2 to usb

I've read that many usb adapters for ps/2 cause latency delay

Are there any adapters that don't suffer or suffer less from this problem?

[tararais]

It should be nearly unnoticeable for any adapter.

[SamirD]

It should be nearly unnoticeable for any adapter.

I second this.  Any good (even just decent) adapter will have almost zero noticability.

[dr_habu]

I might be wrong but, AFAIK, PS/2 will always be faster than USB, and it has nothing to do with the quality of the adapter that you might or might not be using, it's simply a matter of the protocol itself.

You probably already know this, but PS/2 works using hardware interrupts as opposed to USB which is polling keyboard for key presses, so PS/2 will always have lower latency.
Most(if not all) modern keyboards can work in PS/2 compatible legacy mode which is used when four USB pins on the keyboard are connected to four PS/2 pins on the computer, this is most often achieved using a USB->PS/2 adapter(these are dumb adapters that just rewire pins). If you're using a modern keyboard with a controller that supports both USB and PS/2 legacy modes, but has only a PS/2 connector, then going in the opposite direction is also possible - connecting it to USB is just a matter of a dumb PS/2->USB adapter.

If you have an older keyboard that's just PS/2 and doesn't support USB, then you'd have to use an active PS/2->USB adapter(these are also called converters). These things are essentially USB devices that add a USB connected PS/2 port to your computer. They have their own micro controllers that translate the PS/2(actually AT) protocol to USB HID protocol. Due to their nature those devices add some additional latency.

Of course all those additional latencies will only be noticeable when typing very quickly or repeating keystrokes very rapidly. Most people these days use USB keyboards, and they'll never have any latency issues, because the difference between PS/2 and USB latency will never be apparent in day to day use.

However if I'd have to rate ways of connecting a keyboard to a PC starting with those with lowest latency I'd order them as follows:

• PS/2 port on a computer <-> PS/2 keyboard(or a USB keyboard supporting PS/2 legacy mode connected through a dumb adapter)
• USB port on a computer <-> USB keyboard
• USB port on a computer <-> Active PS/2 to USB adapter/converter <-> PS/2 keyboard

The last option would be the slowest in my opinion simply because there are so many layers of signal processing.

I'm sure that someone will correct me if I'm wrong about any of this(and I probably am).

[SamirD]

Actually, I think you're dead-on as this is always the way I've thought of the adapters and ps2 vs usb.  For the record, I believe the keyboard port uses interrupt 2, with interrupt 1 being the highest priority.

The original IBM AT had only 8 interrupts, but this was expanded to 15 with the addition of a second interrupt controller on the 286 and beyond.  Then there was additional stuff done (don't even know what) to get to the modern systems which can have as many as almost 40 interrupts from what I've seen.