31 Dec
2010
31 Dec
'10
6:16 p.m.
Yeah...
I've been steadily working towards getting a working TRS-80
Xenix machine. At the moment, I have enough parts (I believe) to make a
working Model II, and a line on the 68000 board. Unfortunately, the
difficult part to find is a hard disk. I have the Model II host adapter
for the early TRS-80 Eight Meg drive (which is, of course, completely
incompatible with anything else), but no drive. I can't even cobble it
to a regular MFM drive, since the actual disk controller is in the drive
cabinet (I have only the host adapter). Unfortunately, you can't really
run Xenix without a hard drive.
I wonder...
The Model 1/3/4 hard disk system consisted of a WD1001 controller board,
a disk drive and a very simple host adapter (just an address decoder
really). I would not be suprised if the M2 one was similar in concept.
Radio Shack were also very good about supplying technical/service manuals
(one reason I liked their machines, yes even back then I knew the value
of a schematic!), so I suspect some information on the M2 hard disk
system exists.
I wonder how hard itwould be to make up a devie to plug into the host
adapter, appear to have the smae M2-accessible registers, but using some
mode modern storage device. Probsbly a lot easier than replacing an ST412
hard disk, for example. 
31 Dec
31 Dec
6:52 p.m.
Fred Jan Kraan wrote:
The original 8 Meg controller emulated the WD1000
chipset even
before it was on the market. So it should look like something familiar
:-).
The original WD1000 chipset (circa 1980) *was* 8X300-based, and was used
in the first WD1000 controller board as sold by WD. The 8X300 didn't
"emulate" anything, as it was a new design. The WD1000-series of
bipolar MSI support chips did the MFM encode, decode, write precomp,
etc., and the 8X300 was the brains of the operation.
It wasn't until several years later that WD introduced the WD1010 VLSI
controller, which emulated the 8X300-based controller.
Eric
6:59 p.m.
On 31 Dec 2010 at 11:52, Eric Smith wrote:
The original WD1000 chipset (circa 1980) *was*
8X300-based, and was
used in the first WD1000 controller board as sold by WD. The 8X300
didn't "emulate" anything, as it was a new design. The WD1000-series
of bipolar MSI support chips did the MFM encode, decode, write
precomp, etc., and the 8X300 was the brains of the operation.
The juxtaposition of "brains" and "8x300" I must confess, is
something that I never thought I'd see...
--Chuck
8:05 p.m.
Chuck Guzis wrote:
The juxtaposition of "brains" and
"8x300" I must confess, is
something that I never thought I'd see...
The design (originally from SMS) was
somewhat unconventional compared to
other microprocessors of the time, but it made great "brains" for things
that needed to be fast.
Eric
8:30 p.m.
On 31 Dec 2010 at 13:05, Eric Smith wrote:
The design (originally from SMS) was somewhat
unconventional compared
to other microprocessors of the time, but it made great "brains" for
things that needed to be fast.
Perhaps with some of the support chips, it might get to "idiot"
level, but believe me, programming one was an exercise in minimalism.
Basically a move architecture, with one conditional and one
unconditional jump instruction
What's surprising is that the 8x300/305 lasted well into the late
1980s, when other cheaper solutions were available.
--Chuck
9:01 p.m.
On 31 Dec 2010 at 13:05, Eric Smith wrote:
The design (originally from SMS) was somewhat
unconventional compared
to other microprocessors of the time, but it made great "brains" for
things that needed to be fast.
Perhaps with some of the support chips, it might get to "idiot"
level, but believe me, programming one was an exercise in minimalism.
Basically a move architecture, with one conditional and one
unconditional jump instruction From what Iv;e seen, probamming the 8X305 was rather
like writing
microcide.,
A lot of designed (the WD1001 in my 3rd party hard disk for the Model
3/4 is one such) used the 8X305 as a sequencer. The cotnrol store was
wider than the the 16 bits used by said processor, and the extra bits
were decodded and used to directly control hardware. This made it rather
diffenrt to most other microcontrollers
-tony
5111
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ard＠p850ug1.demon.co.uk -
cclist＠sydex.com -
eric＠brouhaha.com -
fjkraan＠xs4all.nl