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Dick Smith System 80 - What do I do next with it? - CheshireNoir - 20-10-2022

Hey Folks,
Got the System 80 set up the other day, and with some help from Terry Stewart's resources, I got video organised and booted it up enough to run the obligatory "Hello World" BASIC programme.
The question I have now is: What next?
Obviously I can download some of the tape images from the Repository and try those out initially, but further down the track, I'd be interested in expanding this machine somewhat.
  1. Should I upgrade the RAM internally to 48K? I see many people seem to piggy-back another two chips on top of the initial 16k. I assume you just tie additional address pins to the Z80 Address pins? Is this really the best approach?
  2. Am I likely to find the S100 bus expander for less than the price of a small family car?
  3. If not, are there any modern expansions for the expansion bus? (Something that does the 32K and a Disk Controller would be nice)
  4. What maintenance will the system need? I inspected the caps and they looked fine.
  5. Is there anything else I should be doing? Anything to improve TRS-80 compatibility, for instance?
This machine was an unexpected surprise so I'm a bit taken aback by it :-)


Cheers, and thanks in advance!

John

RE: Dick Smith System 80 - What do I do next with it? - ChickenMan - 20-10-2022

Well done, a great unit. But what actual model do you have, can we get a photo ?

I would suggest replacing the 4116 memory chips with 4164 following Don McKenzie procedure (will drop it in the Repository shortly).
Do you have UPPER and lower case, if not that could do with an update.
Do you have audio ? If not time to install a speaker and a small amplifier.
Expansion units for the TRS-80 Mod 1 are substantially cheaper out of US, but you need to make a 40pin to 50pin adapter which will give you Floppy drive but not extra Mem. Need to sort the 110volt power supply.

RE: Dick Smith System 80 - What do I do next with it? - ChickenMan - 20-10-2022

Checkout in the /Vintage /System-80 /Documentation / folder for system-80_memory_expansion_procedure.pdf (with thanks to GeorgeK).

RE: Dick Smith System 80 - What do I do next with it? - someone - 20-10-2022

Best to keep it pristine and hook up a 32K SRAM on an expansion board.
It should be pretty easy to do with a single 32K RAM and a decoding GAL.

Piggybacking chips makes it difficult to replace faulty ones and looks messy.

If you want to replace the 4116s with 4164s be aware that 4164 DRAMs don't require the +12V and -5V voltages and that the +5V pin moved to the old +12V pin.
The old +5V pin becomes A7, the old -5V pin becomes NC (No connection)

RE: Dick Smith System 80 - What do I do next with it? - ChickenMan - 20-10-2022

(20-10-2022, 08:27 PM)someone Wrote: If you want to replace the 4116s with 4164s be aware that 4164 DRAMs don't require the +12V and -5V voltages and that the +5V pin moved to the old +12V pin.
The old +5V pin becomes A7, the old -5V pin becomes NC (No connection)

The procedure I mentioned above takes all that into account.  Pretty simple mod really.

RE: Dick Smith System 80 - What do I do next with it? - CheshireNoir - 20-10-2022

Thanks Chickenman!
I believe it's a "Blue Label" with no mods done whatsoever. Certainly it didn't seem to do lowercase when I pressed Shift.
               

Here are some pictures. I'll definitely look at doing a 48K mod.

John

RE: Dick Smith System 80 - What do I do next with it? - RedskullDC - 21-10-2022

Hi John,

Nice find.

Video board on the right is the later model with full 8 bits for screen Mem, so you probably have Lower Case already.
Test with:
10 FOR T = 0 to 255
20 POKE 15360+T,T
30 NEXT T
40 GOTO 40

You also have some kind of expansion ROM fitted in the $3000 area (The ceramic EPROM at the bottom left of the CPU board).

Would be interested to know what is on it?

Try activating it with:

SYSTEM <ENTER>
*/12288 <ENTER>

(Could have different entry points though)

Cheers,
Leslie

RE: Dick Smith System 80 - What do I do next with it? - ChickenMan - 21-10-2022

Yes, definitely a Blue Label Sys80. That extra ROM was standard addition for a Blue Label but can be replaced with other programs, so a dump of it would be good Smile and you will have lower case and sound. I dont think BASIC knows about lower case though.

RE: Dick Smith System 80 - What do I do next with it? - CheshireNoir - 21-10-2022

Thanks Leslie and ChickenMan!
I'll attempt to dump the ROM today, time permitting.

John

RE: Dick Smith System 80 - What do I do next with it? - CheshireNoir - 21-10-2022

ROM Dumped.
I'm guessing some sort of "Enhanced Keyboard" solution from the text in the ROM. There's the line "NEW KEYBOARD ROUTINE ENABLE." visible in the dump.

Hopefully this'll be useful to someone else. For now I need to go and buy a new belt for the tape deck before I can proceed.

John