An MC-10 with 128K!

[Omega-TI]

It's amazing what one finds on the Internet...

 

 

 

 

I guess a lot can be don with the MC-10's expansion port. Here's a basic schematic on the computer.

[BassGuitari]

I think there's a video of this in action on YouTube. Not sure what you'd do with 128K on an MC-10 (bigger/better MC-10 games, I guess?), but why not?

Was this the same guy that created a floppy driver and DOS and loaded stuff from 3.5" disks?

[JamesD]

The upgrade has been around for a while but only a limited number of boards have been made over the last few years.

You can find full details in the MC-10 yahoo group.
ttps://groups.yahoo.com/neo/groups/TRS80MC10Club

The MC-10 has really crappy memory map decoding which would normally make expansion difficult, but the engineer that designed it had the foresight to include a line on the expansion connector that allows expansion boards to disable internal memory mapping.

That doesn't mean you can move existing hardware around to different addresses, you can just disable it from responding.

 

If you really want to upgrade the beast, a 4K upgrade was published in the September '83 issue of Color Computer Magazine shortly after the MC-10 was introduced.
It allows the hi-res graphics modes to be full screen.
The mod consists of 2 SRAMs piggy backed on the existing ones, a couple 74LSXX chips and a bunch of wires if I remember right.

Combine those two upgrades and the MC-10 is decent little machine.

[JamesD]

Just some comments to go with the MC-10 schematic posted above, which btw is the best MC-10 schematic I've seen for understanding how the MC-10 circuitry works.

The two chips that do most of the work are obviously the 6803 CPU/Microcontroller (U1) at the lower left of the diagram and the 6847 VDG (U11) which is the large chip right in the center of the circuit. Note that pin 20 (AO12 - aka Address Output 12) is not connected. This is required for the VDG to address more than 4K of RAM. The hi-res RG6 (Resolution Graphics 6K) and CG6 (Color Graphics 6K) require... 6K. Technically, the VDG could address up to 8K with that many pins but no modes require it.

The next 3 largest chips in the MC-10 are the SRAMs U9 and U10, which provide all of the built in 4K of RAM, and the built in ROM U3. The system comes with only half the ROM the circuit is wired for so pin A12 is not connected to anything. Had Tandy socketed the chip an Extended BASIC or DOS could have been built in but it's unlikely that both would fit at the same time as that took about 24K on the CoCo and even more on the CoCo 3. The MC-10 is wired for 16K of ROM.

The built in RAM is directly attached to the 6847 buss and it's isolated from the 6803 bus so the two don't interfere with each other. The 6847 has no connections to the external expansion buss.
The buss isolation is accomplished with 3 chips. U5, U6 and U7. The first two isolate the address busses and U7 isolates the data busses.

U2 latches (stores) the lower address lines from the data buss prior to using it as the data buss. That is triggered by the CPU AS (Address Strobe?) line on the CPU.

U8 latches settings for the 6847 and toggles the sound output. Pin 15 is the sound output and it leads to the RF modulator. The French Matra Alice is a close copy of the MC-10 but adds a connection between the sound input on the RF modulator and a pin on the expansion connector the MC-10 doesn't use. This allows the addition of an external sound chip on the Alice. I don't know if that includes the first Alice or the later ones that use a different video chip. There is no physical pin on the MC-10 or it could be modded to do the same.

If you look about the 6847, you'll find U18, U19 and U13 which is the clock circuit though I don't actually see the crystal on the diagram though it should be with C30, C23 and R25. U18 and U19 divide the clock and U13 appears to invert in so that the 6847 and 6803 operate on alternate phases of the clock cycle. This keeps internal RAM accesses from colliding.

U4, U13 and U20 do the address decoding and it's pretty incomplete.
The yellow lines leading to the SEL connection on the external expansion buss disables the internal address decoding.

U12 just inverts some signals to make the logic level correct.

The keyboard decoding circuit is in the lower right. You set the lines you want to test on the built in 6803 port and read the address of U14 to check for a connection.

The serial port, cassette, reset, power, RF Modulator and RF out are all labeled and have enough analog circutry to make explanation difficult. However, if you look at the RF modulator, it uses an MC1372 to convert the video output of the 6847 to RF which appears to be filtered (I'm guessing) before leaving the MC-10. This is where a composite interface would be attached.

[JamesD]

...

If you look about the 6847, you'll find U18, U19 and U13 which is the clock circuit though I don't actually see the crystal on the diagram though it should be with C30, C23 and R25. U18 and U19 divide the clock and U13 appears to invert in so that the 6847 and 6803 operate on alternate phases of the clock cycle. This keeps internal RAM accesses from colliding.

...

That's supposed to say "If you look above the 6847"... "appears to invert it so".

Edited March 30, 2015 by JamesD

[carlsson]

If I understand correctly, there still are some unclaimed MCX-128 expansions in the latest batch so if there are any MC-10 or Alice 4K owners on this forum that are not part of the mailing list, it could be a good time to buy one as I'm unsure if any further batches will be made. Of course the most talented ones might cobble together expansions on their own, but for the rest of us it is convenient that someone else did the hard work. Actually I've been toying with the idea to get a second MCX-128 as mine is a bit hacked up as a result of misunderstanding the assembly instructions. Then again, I don't need more than one as long as it still works.

 

Also if the new video modes kick off, in combination with the MCX-128 you can get programs up to 40K or thereabouts, plus the improved graphics. I don't know if there will be a big following of this configuration, but one never knows... 30 years too late the MC-10 might actually turn out to be a decent, compact computer.

Edited April 2, 2015 by carlsson

[JamesD]

Just so people are aware, the MCX-128 doesn't fix the MC-10 hardware so that it can use the two highest res graphics modes, 128x192 4 color and 256x192 2 color..
Only the internal mod I mentioned can do that.
However, the added RAM and BASIC enhancements do let you use the ones that are already there and a lot of games for the CoCo were written for the 128x96 4 color mode anyway because the pixels in the 128x192 4 color mode were rectangular.

The 128x96 4 color graphics mode overwrote part of BASIC with the factory 16K upgrade.
This upgrade adds RAM in the previously unused lower region of the memory map and uses a patched/enhanced BASIC to relocate programs and it adds new commands.
I don't have an MC-10 anymore or I'd probably pick one up, they are only $30.

Here is the posting over in the yahoo group with contact info:
https://groups.yahoo.com/neo/groups/TRS80MC10Club/conversations/messages/5083

If someone would emulate he MC-10 with an MCX-128 it would probably be a popular upgrade.

Personally, if Tandy hadn't neutered the graphics it would be a great compact computer.
With this RAM upgrade and the graphics fix, the machine could run a custom version of the FLEX OS. That's the 6800 equivalent of CP/M.
You can display 51 or 64 characters per line with the 256x192 graphics mode and this had already been done on the CoCo versions of FLEX.
Since the CPU is isolated from the built in RAM on the MC-10 and access can be disabled, an MC-10 could actually have more RAM for FLEX than a regular CoCo.
If the machine had come with 8K and full graphics from the factory you probably would have seen a 64K RAM upgrade that let you use the entire memory map from assembly and people would have been buying these to hack them into better cases with full keyboards as FLEX machines.

A 64 character per line graphics text driver was originally posted in the yahoo group files area back in 2010 and was last updated in 2012.
It should be fast enough to keep up with a 1200 or possibly even 2400 baud modem and there's probably room for more speed optimizations.
Graphics text looks like this, note the mirroring of the top 1/3 of the screen (black text on a white or green background might look better):

Edited April 2, 2015 by JamesD

[pitfall_jerry]

I just bought one a MC-10 and would love to know where can I get one of these kits?

[JamesD]

I just bought one a MC-10 and would love to know where can I get one of these kits?

There's actually a newer upgrade with an sound chip. I don't know if they are shipping yet. Check the yahoo group I linked to above

[pitfall_jerry]

Thanks I will do that. I like the little system it will be fun to play with.

[R.Cade]

If you can remap the whole thing, couldn't they just make it 100% CoCo 1/2 compatible?

[JamesD]

If you can remap the whole thing, couldn't they just make it 100% CoCo 1/2 compatible?

1. The CPUs are not compatible.

2. That's not quite what is going on.

[MrRetroman]

I didn't know the MC-10 memory could be expanded past 16K.

[JamesD]

I didn't know the MC-10 memory could be expanded past 16K.

Radio Shack sold a 16K upgrade which expanded it to 20K.

A hack was published that let you mod that to have even more RAM, but it wasn't available for BASIC outside of using PEEK, POKE, and USR functions.

Edited November 14, 2016 by JamesD

[00WReX]

Check out the Zippster Zone, Ed is the man and he is fantastic.

 

Purchased a few items off him over the years and his products are top quality and his packaging of items is second to none.

 

Currently for the MC-10 he has...

• MCX128
• MC-10 Composite board (NTSC only)
• MC-10 Game Cart
• MC-10 Supercart

https://sites.google.com/site/thezippsterzone/home

 

I have previously purchased a MCX-128 kit from Ed when they were first released.

I just recently purchased 'The worlds first' MC-10 games cartridge.

This has two games built in + a 32K memory expansion, all in a very professional case with sticker.

 

 

 

https://sites.google.com/site/thezippsterzone/mc-10-game-carts

 

And a 'SuperCart' is coming...

 

https://sites.google.com/site/thezippsterzone/mc-10-supercart

 

Cheers,

Shane