RC11 controller (Was: Reproduction DEC 144-lamp indicator panels)

[Guy Sotomayor]

On 12/9/21 8:15 PM, Jay Jaeger via cctalk wrote:
>
> One could perhaps emulate the RS64 data stream using a fast-enough 
> micro, ala the MFM emulator.
>
Why does everyone seem to want to emulate HW like this with a micro when 
a reasonable FPGA implementation with some external FRAM would do the job?

The SMD/ESDI emulator that I've been working on has to "brute force" the 
emulation because of BW concerns.  That is, it has to read the entire 
emulated disk image into DRAM because:

 1. You need at least a track's worth of buffering to send/receive the
    data though the data interface (serial)
 2. You don't have enough time to transfer tracks in/out of the track
    buffer to flash (or what ever) to meet the head switch times
 3. You don't have enough time to transfer whole cylinders in/out of the
    cylinder buffer to flash (or what ever) to have reasonable
    track-to-track seek times

So it will require a micro, but that's mainly to manage what's going 
in/out of the (large) DRAM back to flash (it reads the entire emulated 
disk image into DRAM during boot).  All of the actual commands and data 
movement across the interface are all done by an FPGA.

-- 
TTFN - Guy