1 Dec
2003
1 Dec
'03
6:34 a.m.
1 Dec
1 Dec
8:15 a.m.
On Mon, 2003-12-01 at 20:34, Al Kossow wrote:
With the exception of SMD and ESDI, most small disc
interfaces used an
analog PLL data separator for read data for the drives. There was a LOT
of variation in sector encoding formats (differing ECC schemes, RLL data
encoding, etc.)
Hmm. Non-trivial then! :/
Another problem to consider is how to map sector
lengths that aren't
512 bytes onto modern discs.
Probably not so much of an issue given the speed of old hardware against
modern stuff - multiple sectors could be combined in software on the
modern hardware to represent a single 'unusual' sized sector on the
original equipment at a rate faster than the original host could process
it anyway.
cheers
Jules
9:25 a.m.
----- Original Message -----
From: "Al Kossow" <aek(a)spies.com>
To: <classiccmp(a)classiccmp.org>
Sent: Monday, December 01, 2003 3:34 PM
Subject: Re: Disk hardware emulation, was Re: Grandfather system RTE6/VM?
Doesn't ST506 have analogue elements
to the interface, and a tight
relationship to the host controller with which the drive was formatted?
--
With the exception of SMD and ESDI, most small disc interfaces used an
analog PLL data separator for read data for the drives. There was a LOT
of variation in sector encoding formats (differing ECC schemes, RLL data
encoding, etc.)
Another problem to consider is how to map sector lengths that aren't
512 bytes onto modern discs.
I guess my first question is why use rotating storage? I've been thinking
about this for a while...What I envision is a 'black box' that emulates
the hardware device ex[ected by the host controller. It would have
its own processor to emulate the target hardware and uses a flash
memory card(s) for the actual storage media.
This would have several advantages over using rotating media:
1. By changing the I/O card (has the proper connectors, signals,
and temimnations as the original device) and a eprom any device
could be emulated.
2. Changing OSs would simply be a matter of shutting down the
host system and changing the flash memory card with one containing
the new OS and rebooting the host.
3. One could use existing PC type hardware to load/backup the
flash cards at will.
4. The most important advantage is that NO modification
of the host system would be required.
Let's face it, given the current trends, two years from now
smallest HDs are going to 200GB. It would be kind of silly
to use a drive of that size to emulate a set of RK-05s...
Just some thoughts
Mike
10:24 a.m.
In my little corner of the world, I've built an emulator
for the TRS-80 drives that does FM/MFM (SD/DD). It connects
straight to the TRS-80 floppy cable and looks like a floppy
to the TRS-80. It is loaded from the PC with an RS232
connection and a floppy image in DMK/JV1/3 formats. The PC
software is smart enough to allow you to download a single
file to the emulator by automagically wrapping the file
in an appropriate OS. All of the old TRS-80 OS's are supported,
and CP/M is in the works.
It works with the Model I & III/IV now. I'm adding to the
firmware to do hard sectors so I can boot my H8 from it. Over
time I want the box to be able to boot many of the old machines.
Next on the list after the H8 (which really covers many machines)
is the Apple ][.
I've got the plans up on the web at www.rothfus.com/SVD. Note,
though, that the latest and greatest (including DD) isn't up
there yet. Hopefully over Christmas I'll get the new stuff up
there.
Eric
7474
days inactive
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3 comments
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participants (4)
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aek＠spies.com -
cukr＠massnet1.net -
eric＠rothfus.com -
julesrichardsonuk＠yahoo.co.uk