Soldered. Would be nice to make that easier.
On Saturday, September 3, 2022, B 9 wrote:
> I agree with Birt, those micrograbbers are finicky. How does the wire for
> RexCPM connect securely in the T102?
>
> —b9
>
> On Mon, Aug 29, 2022 at 5:25 PM Stephen Adolph
> wrote:
>
>> Bit of a step
I agree with Birt, those micrograbbers are finicky. How does the wire for
RexCPM connect securely in the T102?
—b9
On Mon, Aug 29, 2022 at 5:25 PM Stephen Adolph wrote:
> Bit of a step forward in terms of REXCPM for T200.
>
> In experiments on a real T200 (not virtualT), I get the following
, August 29, 2022 7:24 PM
To: m...@bitchin100.com
Subject: Re: [M100] REXCPM for Model 200?
Bit of a step forward in terms of REXCPM for T200.
In experiments on a real T200 (not virtualT), I get the following nice result.
Question: What memory is accessed in the "address hole" from
Bit of a step forward in terms of REXCPM for T200.
In experiments on a real T200 (not virtualT), I get the following nice
result.
Question: What memory is accessed in the "address hole" from 8000-9FFF"
when Option ROM is selected (BANK3)?
- ideally CP/M needs a full 64k
- we have ram from
A wire sounds good enough for me. I tried to trace the PCB to figure out
where A15 could most easily be tapped, but the resolution of the PCB scan
from the Tandy 200 Service Manual is too low.
—b9
On Wed, May 25, 2022 at 7:34 PM Stephen Adolph wrote:
> Well,
> Looking at the REXCPM board, it
Well,
Looking at the REXCPM board, it is possible to go from 3 signals on the
jumper to 4.
This would allow for A15 to be brought in, and to identify the special case
where /BANK3 is zero but the address bus is 8000-9FFF.
At first blush I can't think of a good way to solve this other than by
AH, I see your point.
I stand corrected, A15 is not on the socket.
[image: image.png]
So, maybe your suggestion works; is A15 needed at all?
Yes, I think it is needed.
How would you tell the difference between these two addresses, from the
perspective of REXCPM?
vs 8000.
Both have
Couple of comments.
Agree with your rule, but REXCPM is even more fancy.
It supports 32k bank switching in to 7FFF and 2 banks of 16k switched
at 8000 to BFFF and C000 to . So REXCPM has to differentiate a bit
based on which bank is indicated.
All this bank switching to support RAM
Yes, that helps quite a bit. Thank you.
One more question: If you are already handling situations 1 & 3 — bank3 is
low and bank 6 is high for both, so A15 must be checked — why not reduce
the scenarios to a single rule:
- If either bank3 or bank6 is low, address is 0 to , rexcpm responds.
when bank3 is low, address to 7fff, bank6 is high, rexcpm responds.
When bank6 is low, address a000 to , bank3 is high, rexcpm responds
When bank3 is low, address 8000 to 9fff, bank6 is high, rexcpm responds.
All of these scenarios are unique. Cpm gets 64k when option rom and optikn
I'm a little confused.
It sounds like you're selecting on /BANK3 = 0 (option ROM selected) AND
/BANK6 = 0 (expansion RAM selected). But, if I'm reading figure 4-6 from
the service manual correctly, /BANK3=0 AND /BANK6=0 will always be false
because no two banks are ever selected at the same time.
I've been thinking about it too.
/BANK6 is perfect for selecting that ram bank for address A000 to . No
issue.
I believe that , when option rom is selected, it is actually selected for
all addresses from to 9FFF.
Now about A15. It is actually present in the socket because the AD bus
If you can get A15 without a blue wire, it does not seem that you would
need the new select signal based on /BANK6. Requests for 8000 to 9FFF
appear to already go to Bank 3, so you'd just need to detect addresses in
that range in the OPTION ROM. It looks like the service manual schematic
for bank
(Sorry for the random seeming reply. I had thought I had sent that earlier.)
On Wed, May 25, 2022 at 4:49 PM B 9 wrote:
> Let me see if I understand correctly. The main problem is that CPM
> requires the entire 64K of address space to be RAM. For the Model 100,
> REXCPM somehow is able to
Let me see if I understand correctly. The main problem is that CPM requires
the entire 64K of address space to be RAM. For the Model 100, REXCPM
somehow is able to replace both the builtin ROM (0-7FFF) and RAM
(8000-) with its own System RAM. That method will not work for the
Model 200 in
Hey Steve,
This makes sense! Let me know if you plan to proceed and need help with
number 6 below. :)
Ken
On 5/16/22 3:57 PM, Stephen Adolph wrote:
I took a fresh look at the T200 "all ram mode" which would be
needed for REXCPM to work (nicely).
Summary: it is actually feasible I believe
I took a fresh look at the T200 "all ram mode" which would be needed for
REXCPM to work (nicely).
Summary: it is actually feasible I believe to implement an all RAM mode
fairly easily, which would support CP/M nicely.
*Issue 1. The 8k ROM at 8000-9FFF*
* as shown on the schematic, the M15 ROM is
There would have to be a convenient plug and play ideally way to decode
that.
>From what is present in the ram module compartment, I dont see a good
solution.
I'll take another look.
On Sunday, May 15, 2022, B 9 wrote:
> I, too, would love to see RexCPM for the Tandy 200.
>
> I apologize for my
I, too, would love to see RexCPM for the Tandy 200.
I apologize for my ignorance, but why is there a hole? For ROM? Would it be
possible to bank out 8000 to 9FFF and replace it with RAM when running CPM?
—B9
On Sun, May 15, 2022 at 9:44 AM Stephen Adolph wrote:
> Hi
>
> At this time, no.
Hi
At this time, no. It would require some changes due to the unique memory
map in the T200 relative to the M100.
I think the biggest issue is that an all ram mode is not clearly possible.
There would be a hole fro. 8000 to 9FFF. That's not great for CPM.
Steve
On Saturday, May 14, 2022,
Is there an equivalent to the Model 100 REXCPM rom for the Model 200?
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