> Digital Data Stream(1 to 5Mbytes/s) ==> 64Kbytes FIFO (IDT7208 chip) ==> PPI
> Card on ISA[but possible we substitute with PCI such PCI-1751 or PCIO-24 or
> use EPP LPT Port) ==> PC PIII-833MHz==> Save to File
>
> I want to capture the Data Stream to files, and we prefer to do that on
> Linux OS. The problem is,
> 1. Capture Methode from modules
> 2. If we get data directly from user spaces(using ioperm), many data
> some time lost.
I'm built an ISA board last year which uses IDT 720X FIFOs and which I
use in an RT-Linux based high-speed data system. If you are using the ISA
bus, you're NEVER going to get performance beyond 3-5mb/sec no matter if
you use DMA or not. There is a huge penalty for using the ISA bus which
causes each ISA transfer to require about 700ns for each transfer even
though your CPU might be able to execute an instruction in less than ONE
NASASECOND. As best I can tell, the CPU essentially stalls while each ISA
transfer completes. If you do DMA on ISA, you will almost certainly need
to use the mother-board based 8237 type DMA controller.
In my system I used ISA because it's much easier to design and
build than PCI boards, though the performance is *much* lower for DMA and
about 1/2 for programmed IO operations. I also use a high-speed DMA based
PCI digitizer card and with it I have measured DMA transfer rates above
100mb/second for longer blocks of data.
I've looked a long time for basic parallel I/O PCI cards which
support highspeed DMA and so far I've only found one card. It can be seen
at: http://www.modindsol.com/product_detail.cfm?PRODUCTID=136
I bought a couple of the cards, but I hav'nt tried them yet. I
expect them to work well because they are based on the PLX 9080 chip which
is also used by the digitizers I'm using. The 9080 provides two PCI DMA
bus mastering controllers and works very vey well.
W. Wright
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