CF Data Transfer Bandwidth

Hi Sandor,

I have not performed any speed tests but have looked at the Verilog & SOPC Builder timing used to implement that component. It is a very simple interface, with setup/hold/wait-state delays in accordance with the CF specification, using true IDE mode (http://www.sandisk.com/pdf/oem/cf-manual-10.7.pdf). Thus I would not expect the interface to go much slower than CF would natively allow.

However, I have been doing some recent work with CF and have learned a few things:

First, as you mention, there are differences in cards. I have a large 'ultra' card in my digital camera that allows me more continuous 'raw' (6megabyte) shots than a conventional card (the camera can take a few frames a second, buffer to RAM, and then writes to CF...since CF is the slowest part of this eventually it becomes the bottleneck and I have to wait before taking another exposure. I haven't look at the specs of these faster/newer cards but the difference is visible to me.

Second (and perhaps more important), I think performance depends on how efficient the host side software is in its access to the cards, especially if a file system is used. From reading this (http://www.sandisk.com/pdf/oem/appnotecfhostv1.0.pdf) document recently it seems that traditional IDE rules apply: if the file system becomes fragmented, performance goes down. If repeated small file accesses are perfrormed (rather than large files), performance goes down, etc.

If I get to doing any throughput tests (I'm actively working with CF a bit this week) I'll try to post something further.