4 Feb
2001
4 Feb
'01
7:54 a.m.
Heh... I was pondering this morn (whilst making lasagne) about building
a RD52 replacement out of flash memory... I have previously looked at
emulation with a modern IDE hard drive, but gave it up as infeasible...
Anybody have documentation on the data format used by the RQDXx
controllers? I have a datasheet on the controller chip for the RQDX3,
but I'd also like to support the RQDX1 as well....
The basic plan would be thus:
Each track occupies 2^n bytes from a 128MB (or larger flash rom).
The step-in (step-out) signal increments (decrements) a counter
that drives the upper address bits.
After a suitable delay (can anyone say 555 timer) the seek complete
bit is set, and the bits are transmitted in serial fashion from a
fixed clock running at 5MHz (i think).
If write gate is asserted, the bits are latched, at written to the
flash 16 bits at a time, thus giving a write cycle time of 3.2 uS
which should be fast enough. An improvement would be to cache the
write data in a small RAM (32Kx8 is smallest I know of), then write
the whole thing at once during a seek. The tricky part here is
maintaining synchronization with the controller, probably requiring
a PLL of some sort...
Alternately, the data could be de-MFM-ed, and stored just as data,
but this requires re-MFM-ing, and adding address/data marks as well.
It also breaks any diagnostic that wants to write long to force an
ECC error.
I'm still pondering...
clint
PS The board would also need some big power resistors to sink the
32 Watts for RD53 compatability :)
On Sun, 4 Feb 2001, ajp166 wrote:
Anyone have any
idea how hard it would be to build a box with a DIMM in
it
that looked like an RL02?
Zane
I know how but it would take at least three more rounds with the flu to
convince
me of the sanity of doing it..
Consider this both RL02 and ESDI both use a SERIAL data path with a
FORMAT
defined but standard and the media. Thats a hell of a lot of trouble to
go to when disks
in the 32mb and smaller range are easy to find. Sure you get to use
existing drivers
but you have put a immense amount of time in the emulating of the disk so
it interfaces.
To ing it right, and simpler would be sothing like a DRV11 and a couple
of simms
add to that the glue to do refresh and battery back up and you done.
Then you need
a driver.
Allison