25 Jan
2012
25 Jan
'12
3:30 a.m.
The eBay seller never shipped the Model III I won on eBay after 11 days, so I requested a
refund. I left negative feedback (his third in a year) and he got nasty. I told him that
not shipping an item that was paid for wasn't deserving of any but negative feedback.
He felt that not shipping the item and refunding m money was a positive transaction...
*sigh!*
Model III's and 4s are selling from between $400 and $2400 on eBay. These sellers are
mad. I can't say how many Model III's I saw at the old TCF flea markets for
$25.00, stacked 3 or 4 deep. Wish I had bought one...
My Model I is still toast, and my LNW-80 is too big and heavy to setup and use given my
tiny working space. If not for the need to read/write 5.25" floppies, I'd use a
small footprint PC and an emulator. The only 5.25" USB solution
(http://shop.deviceside.com/prod/FC5025) is read-only, It doesn't support TRS-80 Model
I/III/4 formats in any event.
I enjoy seeing all these classic computer re-implementations like Vince Briel's
Replica I, or the DTV C-64 joystick...
I wish someone would reimplement a TRS-80 Model I/III/4 in a chip, like the DTV.
There's nothing special about the Model I really, other than maybe the WDC disk
controller chip. The Model III is little different, it's only the Model 4 with Hi-res
graphics and such where it gets more complicated.
A fellow in Australia wrote to me years ago that he was working on one, but I never heard
back from him.
in the early 90's there was a board that basically replaced the Model I system board
and put a full Model III in the case. It was called a "Trash Compactor." I wish
I had bought one on those...
If anyone knows of such a project, let me know. Or, if you know of a Model I, III or
4?(preferred in reverse order) in the mid-New Jersey area available for sale or trade at a
price someone on a fixed income can afford.
I would have thought SOMEONE would have made a universal USB to floppy drive adapter that
one could use to add a 5.25" drive (or a 3.5") like all of the ATA/SATA adapters
out there.
I'll keep checking eBay for a machine, I found the LNW-80 (only a Model I, not the
Model II which has CP/M and 80 columns) after searching a long time. So, I haven't
given up hope.
Thanks!
Al Hartman
Keansburg, NJ
25 Jan
25 Jan
9:19 p.m.
Model III's and 4s are selling from between $400
and $2400 on eBay. These=
How mauch are M4's going for then?
I used an M3 for several years until I got an M4 (older version CPU board
without the large gate array chips -- the only custom part is the video
timing chain [1]). I've not found anything the M3 could do that I can't
also do on the M4, and the 80 column display and ability to run CP/M cabn
be useful.
[1] This is not a 6845, for all it has much the same pinout. It's a
mask-programemd thing, you don't write to all the configuations
registers, that's what the mask programming defines. The pin that would
be the light pen siganl on a 6845 selects between 2 possible
configurations (here used for 64 colun or 80 column modes).
-tony
11:16 p.m.
I had a Model 4p, but I lent it to STEVE ALBANY and he never gave it back.
A shame, I loved that computer...
On Wed, Jan 25, 2012 at 9:19 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
--
Yoyodyne Propulsion Systems: "The Future Begins Tomorrow"
Visit us at: http://www.yoyodyne-propulsion.net
--------
"Yes, Obama duped young people by not doing every single thing they want.
So now, they'll all vote Republican. It's like when I want some bread, I
won't settle for half a loaf. Instead, I will have a muffin made of broken
glass."
-Stephen Colbert
Model
III's and 4s are selling from between $400 and $2400 on eBay.
These=
How mauch are M4's going for then?
I used an M3 for several years until I got an M4 (older version CPU board
without the large gate array chips -- the only custom part is the video
timing chain [1]). I've not found anything the M3 could do that I can't
also do on the M4, and the 80 column display and ability to run CP/M cabn
be useful.
[1] This is not a 6845, for all it has much the same pinout. It's a
mask-programemd thing, you don't write to all the configuations
registers, that's what the mask programming defines. The pin that would
be the light pen siganl on a 6845 selects between 2 possible
configurations (here used for 64 colun or 80 column modes).
-tony
26 Jan
26 Jan
12:07 a.m.
On Wed, Jan 25, 2012 at 4:19 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
> Model III's and 4s are selling from between
$400 and $2400 on eBay. These=
Ouch!
I used an M3 for several years until I got an M4
(older version CPU board
without the large gate array chips -- the only custom part is the video
timing chain [1]). I've not found anything the M3 could do that I can't
also do on the M4, and the 80 column display and ability to run CP/M cabn
be useful.
When I was in High School, we had two TRS-80s for the "Computer Math"
class - an M3 and an M4. I did not know at the time about CP/M
options, so I ran some ordinary flavor of TRSDOS on them, whatever the
teacher handed us. ISTR preferring the M4 over the M3 when given the
opportunity, but it's been long enough that I can't remember why
(keyboard tactile feedback or monitor ripple or something trivial -
don't think it was software or firmware-related - we had the same OS
disks for both).
I should see about tracing down the memory fault on my M3 - I've tried
memory tests and moving the 4116s around, but it seems to only see 32K
of the 48K that's installed. It's possible that a '157 or something
further upstream from the DRAM is faulty.
-ethan
8:31 p.m.
When I was in High School, we had two TRS-80s for the
"Computer Math"
class - an M3 and an M4. I did not know at the time about CP/M
options, so I ran some ordinary flavor of TRSDOS on them, whatever the
teacher handed us. ISTR preferring the M4 over the M3 when given the
opportunity, but it's been long enough that I can't remember why
(keyboard tactile feedback or monitor ripple or something trivial -
don't think it was software or firmware-related - we had the same OS
disks for both).
As far as I know, a Model 4 will boot any Model 3 disk/operating system,
at which point it hehaces like a Model 3, you don't get any of the extra
features. So if you were using an Model 3 TRS-DOS operating system, you
wouldn't have had the 80- column screen or the extra memory or...
The keyboard has some extra keys, but an M3 OS won't make use of them.
There were several differnet keyboards used over the production time of
the machines, perhaps the M4 had one you liked better the the one on the
M3. My M3 and M4 have essentially the same keyboard, the one using
individual Alps switches.
The case colour is different (M3 is grey, M4 is white). I can't believe
that made any differece
The video monitor is the same circuit, so is the PSU. So there shouldn't
ahve been any more or less ripple.
However, the M3 has a white phosphor CRT, the M4 has a green one. Of
coruse the CRT can be changed, but if the machiens were 'stock', that's
the most obbvious thing that you might care about.
I should see about tracing down the memory fault on my
M3 - I've tried
memory tests and moving the 4116s around, but it seems to only see 32K
of the 48K that's installed. It's possible that a '157 or something
further upstream from the DRAM is faulty.
Obvious things would be address decoding or the RAS/CAS drivers.
-tony
10:27 p.m.
However, the M3 has a white phosphor CRT, the M4 has a green one. Of
coruse the CRT can be changed, but if the machiens were 'stock', that's
the most obbvious thing that you might care about.
C: I had a 128k version model 4 (presumably). It had a amber screen. I sold it.
27 Jan
27 Jan
8:53 p.m.
However, the M3 has a white phosphor CRT, the M4 has a green one. Of
coruse the CRT can be changed, but if the machiens were 'stock', that's
the most obbvious thing that you might care about.
C: I had a 128k version model 4 (presumably). It had a amber screen. I
I qam pretty sure the only 'official' way to get 128K in a Mdoel 3 was t
o upgrade it to a Model 4 :-)
sold it.
As for the CRT, I don't recall Tandy/Radio Shack ever shipping machines
with amber CRTs. But I do recall an advert in Byte (and I assume in other
magazines) for a complany that supplied amber CRTs to upgrade carious
monochrome computers/terminals, and IIRC the M3/M4 was one of them. It's
very likely your machine had had the CRT replaced at some point. As I've
said several tiems, these mono CRTs are prrtty generic and thus it would
be easy to fit a non-original CRT with, say, a different phosphor.
-tony
26 Jan
26 Jan
10:37 p.m.
On Thu, Jan 26, 2012 at 3:31 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
If I had a 9000A-Z80 pod for my 9010A, I'd probably already have it
fixed (I probably use my Fluke for testing memory more than any other
single thing - even back in the day, a "DMA test" for a COMBOARD was
really just running a memory test on the quadrant of 68K memory space
that caused Qbus/Unibus DMA transactions... we could test local ROM,
local RAM, or remote RAM via DMA, all with the same buttons and the
same tool). Fortunately, I have a 6502 pod as well as a 68000 pod, so
the Fluke has plenty of targets at my house.
Yes... there are other ways to run address testing, bus testing,
etc... they are more work than popping the processor, plugging in a
vintage purpose-built tester and hitting well-understood buttons. The
lack of a Z80 pod pushes this project further down the stack,
especially since I have little software for the M3 that requires more
than 32K.
-ethan
The video monitor is the same circuit, so is the PSU.
So there shouldn't
ahve been any more or less ripple.
I more meant that one might have been in nicer shape than the other
one, not that one was designed better.
I should see
about tracing down the memory fault on my M3 - I've tried
memory tests and moving the 4116s around, but it seems to only see 32K
of the 48K that's installed. ?It's possible that a '157 or something
further upstream from the DRAM is faulty.
Obvious things would be address decoding or the RAS/CAS drivers.
27 Jan
27 Jan
8:56 p.m.
fixed (I probably use my Fluke for testing memory more
than any other
single thing - even back in the day, a "DMA test" for a COMBOARD was
really just running a memory test on the quadrant of 68K memory space
that caused Qbus/Unibus DMA transactions... we could test local ROM,
local RAM, or remote RAM via DMA, all with the same buttons and the
same tool). Fortunately, I have a 6502 pod as well as a 68000 pod, so
the Fluke has plenty of targets at my house.
Rignt.... I sued to wish fo the 'right' test gear for every problem, then
I realised you got a lot more done using what you have :-)
Yes... there are other ways to run address testing,
bus testing,
etc... they are more work than popping the processor, plugging in a
vintage purpose-built tester and hitting well-understood buttons. The
lack of a Z80 pod pushes this project further down the stack,
especially since I have little software for the M3 that requires more
than 32K.
I think i'd start witha loop (in BASIC or machine code) that accesses a
location in the top 16K of RAM and check that all the address, data, RAS
and CAS pins to these RAMs are toggling (just iwth a simple logic probe).
You'll pick up sillies like a defecctvie driver IC that way.
-tony
26 Jan
26 Jan
11:52 p.m.
In the early 1980s, one of our college administrators had all of our model
3s CONVERTED into model 4s. Doing each one was only slightly more
expensive than buying model 4s to use in addition to the 3s.
4731
days inactive
4733
days old
9 comments
6 participants
participants (6)
-
alhartman＠yahoo.com -
ard＠p850ug1.demon.co.uk -
chrism3667＠yahoo.com -
cisin＠xenosoft.com -
ethan.dicks＠gmail.com -
john＠yoyodyne-propulsion.net