10 Dec
2003
10 Dec
'03
3:27 a.m.
On Wed, 10 Dec 2003, Patrick Finnegan wrote:
On Wednesday 10 December 2003 11:27, Peter C. Wallace
wrote:
I was not considering a design that would be limited to any particular drive
type, but rather that the logical "front end" of the emulator could be tweaked
for best performance by tailoring it to the specific drive. The actual
hardware to do the bitstream processing would most easily be done in a FPGA
so any changes would not require hardware modifications.
Heres what I envision:
A small (say 4x5") circuit card with a FPGA, a SDRAM SIMM socket (or
soldered-on SDRAM), an IDE drive interface, FPGA core power supply, and
perhaps built in level shifters and connectors for at least ST506, Q2000, and
SMD drives. A daughter board connector is provided for more exotic drive
hardware interfaces (RLxx HP79xx etc). The FPGA config could be downloaded
with a serial port or USB.
I guess Tony convinced me of the simplicty of the shift register track data
recording, but compression is still valuable for performance reasons - the
data can be easily compressed before storing in the IDE drive...
On Wed, 10 Dec 2003, Patrick Finnegan wrote:
Not being an 'expert' in data encoding schemes for hard drives, I can't
claim with 100% certainty... but I'm willing to bet there's systems out
there that use things such as GCR (similar to the Apple ][ and
Commodore floppy disk encoding schemes).
Also, you'd have to take into account in your scheme that the data rate
for different controllers may not match. For example, recording data
on the 8" hard drive in the Televideo TS816 probably isn't the same
'data rate' as a common ST506 interface drive, even though the
interfaces are similar.
To me, it's pointless to create a design that's arbitrarily limited to
just one encoding scheme if you don't have to. When you can simplify
the design *and* make it more universal, why not? "Knowing the encoding scheme" prevents
this from being a
"universal" interface. You'd need to make different version for,
say, your PC/XT, your PDP-11 with an RQDXn, and TeleVideo TS816.
(Or shouse I say "my" as those are all system I have that'd benefit
from this). At most, (I think) you'd need a different cable set
for all three of these if you didn't claim to "know" the encoding.
No, thats not true, all you need to know is the encoding scheme...
The cabling is interface type specific.
Pat
--
Purdue University ITAP/RCS
Information Technology at Purdue
Research Computing and Storage
http://www.itap.purdue.edu/rcs/
Peter Wallace
Mesa Electronics