23 Jan
2023
23 Jan
'23
5:22 p.m.
I don't even remember signing up for the RetroAbout64K mailing list. I haven't
seen any actual dicussion in my remembrance. But I do get once or twice a week an email
about COCO Nation or some such. Sounds like a hot chocolate enthusiasts group seeking
world domination. Anyway I've had COCOs going back. Or 1 that I scarfed from a friend
for 20$ (back in 89 I think). I realize it has a 6809 and all, the successor to the
venerable 6800. But what can you do with the things? Is there even a color output, despite
the name. I can't remember. I only remember playing Dungeons of Daggorath or whatever.
The guy I bought it from claimed he programmed a complex naval similation. Yeah whatever.
23 Jan
23 Jan
5:45 p.m.
On 1/23/2023 11:22 AM, Chris via cctalk wrote:
I don't even remember signing up for the
RetroAbout64K mailing list. I haven't seen any actual dicussion in my remembrance. But
I do get once or twice a week an email about COCO Nation or some such. Sounds like a hot
chocolate enthusiasts group seeking world domination. Anyway I've had COCOs going
back. Or 1 that I scarfed from a friend for 20$ (back in 89 I think). I realize it has a
6809 and all, the successor to the venerable 6800. But what can you do with the things? Is
there even a color output, despite the name. I can't remember. I only remember playing
Dungeons of Daggorath or whatever. The guy I bought it from claimed he programmed a
complex naval similation. Yeah whatever.
The CoCo uses the 6847, so color is available. (CoCo3 uses an AsIC that
supports much of the 6847 capabilities, but adds in more resolution, RGB
output, and more colors in those resolutions).
The 6809 runs OS9, so there's that.
Jim
--
Jim Brain
brain(a)jbrain.com
www.jbrain.com
5:51 p.m.
I never knew there was a 6847. The 6545 used in the TI Pro is compatible to whatever
degree with the 6845 despite producing 100 more lines of revolution. The 6847 not so.
5:53 p.m.
The original coco had an MC6809E processor (a slight variation of the
MC6809 processor), a MC6883 Synchronous Address Multiplexer and a MC6847
Graphics Chip.
The 6883 SAM was the "glue" that provided all of the timing and address
decoding for the entire system. To reduce flicker the 6847 and 6809E
memory accesses were alternate cycled. This means that they used
opposite edges of the Phase 1 clock to access memory. However, this
meant running the system at .8949 MHz. The SAM had the ability to run
the CPU at twice that speed but this resulted in the video being disabled.
The 6883 SAM could address up to 96K of memory but to populate that much
memory required after market modifications.
There are many programs and peripherals available for the Color
Computer. The floppy disk system used 5 1/4" diskettes and could run
operating systems like Flex, Star DOS and OS/9 Level 1. I don't recall
if OS/9 Level II was ported to the Color Computer.
I believe there was even some kind of hard disk drive interface
available, though not from Tandy IIRC.
The audio cassette interface used 1200Hz/2400Hz tones to represent ones
and zeros.
There are many Color Computer enthusiast groups all over the country and
people still make add-ons and software for it.
Please just google Tandy Color Computer.
On 1/23/2023 11:22 AM, Chris via cctalk wrote:
I don't even remember signing up for the
RetroAbout64K mailing list. I haven't seen any actual dicussion in my remembrance. But
I do get once or twice a week an email about COCO Nation or some such. Sounds like a hot
chocolate enthusiasts group seeking world domination. Anyway I've had COCOs going
back. Or 1 that I scarfed from a friend for 20$ (back in 89 I think). I realize it has a
6809 and all, the successor to the venerable 6800. But what can you do with the things? Is
there even a color output, despite the name. I can't remember. I only remember playing
Dungeons of Daggorath or whatever. The guy I bought it from claimed he programmed a
complex naval similation. Yeah whatever.
6:11 p.m.
On 1/23/2023 11:53 AM, Mike Katz via cctalk wrote:
The 6883 SAM was the "glue" that provided all of the timing and
address decoding for the entire system. To reduce flicker the 6847
and 6809E memory accesses were alternate cycled. This means that they
used opposite edges of the Phase 1 clock to access memory. However,
this meant running the system at .8949 MHz. The SAM had the ability
to run the CPU at twice that speed but this resulted in the video
being disabled.
Are you sure about that? The system could be sped up, which
involved
not refreshing DRAM, but all of the support ICs and the DRAMs are 1MHz,
so I don't think 2MHz was possible on the CoCo, at least.
There are many programs and peripherals available for the Color
Computer. The floppy disk system used 5 1/4" diskettes and could run
operating systems like Flex, Star DOS and OS/9 Level 1. I don't
recall if OS/9 Level II was ported to the Color Computer.
Yes, it was, but only for the CC3, which had an MMU (don't shoot the
messenger, that's what Radio Shack called it) and 128kB of DRAM, with an
option to expand to 512kB.
The source has been open sourced and extended as "NitrOS9", and there's
a current "Ease of Use" edition that can be loaded from a CoCoSDC and
also has 6309 extensions for faster operation.
I believe there was even some kind of hard disk drive interface
available, though not from Tandy IIRC.
GlensideIDE, sold in the day by the still
active Glenside Color Computer
Club (GCCC) in Chicago, IL. Also, Cloud9's SuperIDE was also sold.
There was a "Burke and Burke" HDD interface that consisted of an
adapter, an ISA MFM card (as I recall), and an MFM drive
Please just google Tandy Color Computer.
Yep.
THere's a half dozen FB group, a Discord Channel, and a mailing list.
Jim
7:21 p.m.
On 1/23/2023 12:11 PM, Jim Brain via cctalk wrote:
Thank you for clearing up the CoCo 3, I never had one. I know the
MC6887 could address and handle the refresh for 96K.
On 1/23/2023 11:53 AM, Mike Katz via cctalk wrote:
I don't recall if that was the CoCo 2 or CoCo 3 but the system could
handle 1.8MHz (with a MC68B08E CPU). The memory had to be 2MHz to
handle the alternate cycling.
The straight MC6809 (non E version) used a more forgiving quadrature
clock but could not be alternate cycled.
The 6883 SAM was the "glue" that provided all of the timing and
address decoding for the entire system. To reduce flicker the 6847
and 6809E memory accesses were alternate cycled. This means that
they used opposite edges of the Phase 1 clock to access memory.
However, this meant running the system at .8949 MHz. The SAM had the
ability to run the CPU at twice that speed but this resulted in the
video being disabled.
Are you sure about that? The system could be sped up, which involved
not refreshing DRAM, but all of the support ICs and the DRAMs are
1MHz, so I don't think 2MHz was possible on the CoCo, at least.
There are many programs and peripherals available for the Color
Computer. The floppy disk system used 5 1/4" diskettes and could run
operating systems like Flex, Star DOS and OS/9 Level 1. I don't
recall if OS/9 Level II was ported to the Color Computer.
Yes, it was, but only for the CC3, which had an MMU (don't shoot the
messenger, that's what Radio Shack called it) and 128kB of DRAM, with
an option to expand to 512kB.
The source has been open sourced and extended as "NitrOS9", and
there's a current "Ease of Use" edition that can be loaded from a
CoCoSDC and also has 6309 extensions for faster operation.
OS9 Level II was designed by Motorola and Microware and made full use of
the capabilities of the 6809 architecture. With simple Dynamic Address
Translation 1MB of extended address space was available.
I used to run OS9 Level II on a Gimix 6809 system and then on a
Hazelwood 6809 System. Running on Dual 5 1/4" floppies, Dual 8"
floppies, a 5 1/4" hard disk drive and a syquest removable 5 1/4" drive.
I wrote the OS/9 Level II drivers for the Gimix DMA Floppy Disk
Controller back in the 1980/1981 time frame.
It's too bad but those systems are long gone and now I play with my
PDP-8 😁.
I believe there was even some kind of hard disk drive interface
available, though not from Tandy IIRC.
GlensideIDE, sold in the day by the still active Glenside Color
Computer Club (GCCC) in Chicago, IL. Also, Cloud9's SuperIDE was also
sold. There was a "Burke and Burke" HDD interface that consisted of
an adapter, an ISA MFM card (as I recall), and an MFM drive
Please just google Tandy Color Computer.
Yep.
THere's a half dozen FB group, a Discord Channel, and a mailing list.
Jim
10:13 p.m.
On 1/23/2023 1:21 PM, Mike Katz wrote:
Thank you for clearing up the CoCo 3, I never had one. I know the
MC6887 could address and handle the refresh for 96K.
I'll have to read up more on SAM. I know it can have 96 memory, but I
thought is was 64kB RAM and 32kB ROM.
OS9 Level II was designed by Motorola and Microware and made full use
of the capabilities of the 6809 architecture. With simple Dynamic
Address Translation 1MB of extended address space was available.
The CoCo 3 could only do 512kB, due to the translation granularity being
8kB and the GIME DAT only have 6 bits. But, back in the day and today,
there are solutions to extend that to 8 bits per translation, which
brings up to 2MB. CoCo 3 based L2 OS9 only supports up to 2MB
natively. There is a few > 2MB options, but OS9 can currently only use
the >2MB as a RAM disk.
Jim
On 1/23/2023 12:11 PM, Jim Brain via cctalk wrote:
I stand corrected:
"Switching the SAM into 1.8 MHz operation gives the CPU the time
ordinarily used by the VDG and refresh. As such, the display shows
garbage; this mode was seldom used. However, an unusual mode available
by the SAM is called the Address Dependent mode, where ROM reads (since
they do not use the DRAM) occur at 1.8 MHz but regular RAM access occurs
at .89 MHz. In effect, since the BASIC interpreter runs from ROM,
putting the machine in this mode would nearly double the performance of
a BASIC program while maintaining video display and DRAM refresh. Of
course, this would throw off the software timing loops and I/O
operations would be affected. Despite this, however, the "high speed
POKE" was used by many BASIC programs even though it overclocked the
hardware, which was only rated for 1 MHz operation. "
Note that the CC3 had a speedup poke that was different and did in fact
speed the entire system with video intact.
On 1/23/2023 11:53 AM, Mike Katz via cctalk
wrote:
I don't recall if that was the CoCo 2 or CoCo 3 but the system could
handle 1.8MHz (with a MC68B08E CPU). The memory had to be 2MHz to
handle the alternate cycling.
The 6883 SAM was the "glue" that provided all of the timing and
address decoding for the entire system. To reduce flicker the 6847
and 6809E memory accesses were alternate cycled. This means that
they used opposite edges of the Phase 1 clock to access memory.
However, this meant running the system at .8949 MHz. The SAM had
the ability to run the CPU at twice that speed but this resulted in
the video being disabled.
Are you sure about that? The system could be sped up, which involved
not refreshing DRAM, but all of the support ICs and the DRAMs are
1MHz, so I don't think 2MHz was possible on the CoCo, at least.
The straight MC6809 (non E version) used a more forgiving quadrature
clock but could not be alternate cycled.
Actually, the 6809E is the Q/E clock version. The 6809(non e) is the
crystal based one.
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