What would your ideal upgrade be right now for your Amiga(s)

[platon42]

Well, you know the other problem for high speed USB is that it is very interrupt heavy. When transferring large amounts of data from one high speed USB hard drive to another on my PC, I can track the interrupt overhead by watching /proc/interrupts. Servicing said interrupts ties up the CPU, which on linux shows up as abnormal amounts "%sy" (system) CPU.

So, even assuming we had a fast enough bus to put a high speed USB2 controller on, we'd probably find that the classic amiga hardware can't service the interrupts fast enough to get it going at full speed (high speed ethernet has the same problem too, but the packets are bigger and therefore fewer are generated per unit of data transferred).

You recognize that the Deneb is a High Speed USB 2.0 card available for years now that can have a throughput of over 8.5 MByte/sec on an Amiga Classic system? And about the interrupts: well, it very much depends on the controller and the driver. The Deneb transfers double buffered chunks of 24 KB each per interrupt. That's a lot bigger than your average 1500 Byte Ethernet frames... Even the Subway/Highway does not cause an interrupt for every 64 bytes transferred...

[platon42]

Which is certainly impressive, but 8.5MB/s, whilst fast for a classic Amiga is not high speed as per USB2 standards for bulk transfers, ~30MB/s is. My reply was on the basis of achieving the latter, ie USB2 transfer rates comparable to what everybody else is used to.

Of course, but that's an implementation issue. There's not a lot in the standard that I'm aware of that dictates how much data a hardware device should buffer. I've seen USB2 controllers that will happily generate an interrupt every packet. Likewise, I've seen ethernet adapters that seem to implement a sensible degree of buffering and don't produce quite the same overhead - very important given the speeds they can reach.

You know that most Amiga classic systems have a memory bandwidth in one direction (i.e. read OR write) of often less than 15 MB/sec? Let alone a transfer between TWO ports (i.e. read AND write). Did you ever benchmark the USB bulk performance of real USB devices? Then you would know that the theoretical 30 MB/sec raw bandwidth of the USB spec are not reached in practice. Even on a Pegasos or MacMini, I never got much faster than around 23 MB/sec.

And the fact that some Windows deseased USB devices only support single USB transfers of up to 64KB does not really help it (there is no such limit defined in the Spec).

Get real, USB1.1 maxes out at 1MB/sec, and everything over that is USB2.0 highspeed.