Tha nk you for the reality check. I had been working off the specs so it is good to know. Well, as it's digital audio it wouldn't be continuous in that you'd rarely use all 4 interfaces (2 in 2 out) but you should be able to and it sounds like it won't work, or at least not unless your pretty lucky. I think I might get around the problem by making it more modular. I can have a hub unit with 3 external downstream ports which can be a "USB legacy breakout box". It would replace most of your legacy ports. Thus you could have: 2 MIDI ports 2 serial ports 1 keyboard port 1 printer ports An MPEG audio port if you so desired (I like the idea of near CD quality audio with no soundcard usage, almost no CPU usage (pump about 25Kb/s over USB) and almost no USB bandwidth and if I'm lucky no driver writing (at least not for wintel)) 3 downstream ports All of these should fit quite comfortably into a low speed 1.5Mbps link (Without EPP on the printer port tho). I didn't do the sums, but you're unlikely to use em all at once. Then you could have 2 digital audio interfaces with 1 In and 1 Out. You wouldn't be able to run both off one USB port. But you should be able plug one into the hub (and a couple of low bandwidth devices that aren't used too regularly (e.g. a USB camera)) and one into your other USB port. A 1 In, 1 Out device should also work on the Intel chip shouldn't it. You could also set up a FPGA as a buffer between the MCU and the DACs/ADCs/Decoders. Then you wouldn't need to worry so much about the buffer filling up or about the status of the DAC/ADC/Encoder. Tom. ----- Original Message ----- Subject: Re: USB PICs (or Digital Audio via USB & MCU) > If the ~10.5Mbit/s is continuous USB bandwidth required, > > a) The Bus is going to be struggling > b) The Intel device would be struggling > c) You have to guarentee that the whole USB is available > Some people have other devices on the USB. > Upto 126 other devices :-) > d) From my personal experience, getting 5Mbit/s from the > USB is all I'd try for in a real world situation. > And that's with a parallel interface, DMA and/or probably with a > 100MHz Scenix on the device end. > This is written only as a reality check > > -----Original Message----- > > From: Thomas Brandon [SMTP:tom@PSY.UNSW.EDU.AU] > > Subject: Re: USB PICs (or Digital Audio via USB & MCU) > > > - At least 1 if not 2 channels of DAT quality I/O (24 bit, 48kHz, > > stereo > > x 4 = 1152 Kbyte/s. 2 isochronous capable endpoint pairs) > > - 2 MIDI I/O (4x ~30000bps max. = 15Kbytes/s. 1 endpoint pair.) > > - 1 channel of MPEG/AC-3 compressed audio (<200bit/s = <25Kbytes/s, 1 > > isochronous endpoint (output only).) > > - Full control over both audio and MIDI interfaces (at least 1 control > > endpoint (BTW: anyone know if I can do the control for both MIDI and Dig. > > Audio on 1 endpoint?)) > > Total: 1300Kbytes/s (not including protocol overhead) = ~10.5Mbit/s > > > One product I am looking at carefully is the Intel > > USB MCUs.