fastest possible USB

Look at the Cypress cy7c68013a

--
Uwe Bonnes                bon@elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik  Schlossgartenstrasse 9  64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------

Colin,

I think a PCI interface capable of bus mastering will still be faster than a USB2.0 interface.

The PCI performance is slightly un-deterministic as it depends what else is on your bus, but from what I've read here over the years I think 80MB/s is a reasonable expectation.

I half remember reading that although USB 2.0 gives you 460(?) Mb/s that this doesn't directly translate ~ 460/8 MB/s of data through-put (ie 60MB/s).

Nial.

------------------------------------------------------------- Nial Stewart Developments Ltd FPGA and High Speed Digital Design

Something else you may want to think about is a dual-port interface to an extarnal USB2 HD, i.e. FPGA to IDE, and IDE to USB2 using one of the standard chips available for this. This would have the advantage of more deterministic timing and probably higher throughput.

I'll add to that and say that the USB controller in the PC is probably sitting on a PCI bus or at least affected by the traffic on it. Also worth saying fastest USB is 480 MBit/s excluding overheads and 32bit/33MHz PCI is

1056 MBit/s excluding overheads.

John Adair Enterpoint Ltd. - Home of Broaddown2. The Ultimate Spartan3 Development Board.

colin a écrit :

My two cents :

You might instead consider implementing a simple IDE hardware interface, the protocol is quite straighforward if you stick to PIO mode (no DMA, however you can reach almost 15 Mbytes/sec, which is close from what you usuallay with an USB drive).

The amount of effort needed to implement the IDE interface might actually be lower than trying to interface with an external USB bridge

Here is a link to a open-source IDE controller IP core

I don't know how efficient it is (we rolled our own).

Hope it can help ...

Steven

We recently implemented a design that moved to a PC using USB 2.0

We used a Spartan3 coupled to a Cypress FX2 part and were able to achieve

30MB/sec transfer rates. It took careful driver development on the PC to get the performance level up high enough.

It was a fun project, but the Windows driver development took a lot longer than expected - it was tricky to get the performance up to where we needed it.

John Providenza

How fast do you expect to go? How fast is your disk? How fast is your USB? How fast is your PCI?

My guess is that your disk is the limiting factor. If your PCI bus is twice as fast as your disk, then you can read the bits into memory and write them out to disk. If you have a driver for your USB gismo, that's probably the simplest overall.

Write some hack code to test/measure it. If anybody needs it, I'll dredge out some linux/unix code that I used to measure disk transfer rates. (Hint: The outside edges are much faster than the inside edges.)

--
The suespammers.org mail server is located in California.  So are all my
other mailboxes.  Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer's.  I hate spam.

Actually.. its not the PCI or USB that will kill you.. its the hard disk write speed. 28 Mbytes/sec to 58Mbytes/sec

Simon

is

than

is

That depends if you have a RAID array but certainly a restriction on signle disk systems.