Richard,

[Just a request: please repair the formatting of your previous post.]

I still have questions, if you don't mind.

First of all, I suddenly realized what you are talking about all the time: you want to capture the formatting process - I am surprised, I thought you want to read the old disks...

I guess you want to do the latter, too, but only after you have determined what is exactly the format written (gaps etc.), isn't it?

And, you want to capture the whole process of it, possibly several hundreds of megabytes of data (after the 8x oversampling), am I right?

So, just an idea, what about using a SDRAM, which today come at sufficient speed and capacity very cheap? It might appear that you'll need a controller for that, maybe implying an FPGA or so, but maybe there might be simpler paths to go, if it's usage is constrained to two modes or so. This is a pure guesswork and would need to look at the details closer, but it was you who wanted fresh, unconventional, and completely weird ideas, isn't it... :-)

Jan