Katerpillar Attack Cartridge for the Tandy CoCo

[pser1]

Hello rolo,
I include a zip file containing a .VDK in wich you will find a Basic program that loads a ROM from disk to a fixed RAM position.
Then calls a small m/l routine that switches to RAM map and copies BASIC there and the ROMM too, then runs the ROM at $C000
Hope it will help
best regards
Pere

[Rolo]

Thanks Pere,
if I understand correctly that tool needs ram in the upper bank?
It's not that I absolutely must have that rom, it's just that I want to know what is the reason for the strange behavior of that rom.
And I know more in the meantime. Btw., it's in reality just a 4k-rom and it obviously touches the limits of the XRoar-emulation (which is excellent), since hardware and software do not show the same result. Or vice-versa my D32 might be a little bit out of spec(?). What a pity, I just have a single machine. Sometimes I'd need a second one for testing. ( Should I get a brand new Tano? Ah no, not another one, I really have no room anymore! Hmmm ) I can launch it now on my D32, with a little trick. Still have not understood 100%, but I try to track it down. I'll tell you, as soon as I know...

[pser1]

Helo rolo,
My vdk is a way to try ROMs in a Dragon 64, that is to say i n 64K RAM mode.
If you have a Dragon 64, i will hardly recommend you to use my 'trial version' because it works in RAM, so that you can change there the bytes you want and make as many test as you need,
so you don't need to burn EPROMs no more if you just want to make tests.
By the way, I won't promise a lot of time to work with, but if you could post your EPROM, i will try to give it a run. Don't expect nothing from that, anyway I will try to make my best.
best regards
Pere

[Rolo]

Thanks, for the help. I just have to do some little tests before that. Maybe I already have the solution...

Btw. my Dragon is a D32, which I upgraded to 64kBytes, but Basic and Kernel are still D32. So, I have an upper bank, which is good for "duplidisk".
For example the RAM-tests of all the diagnostic cartridges (Tandy and Dragon) are crashing on my machine, but I do not think that I've got a real RAM-malfunction anywhere. That machine is running without problems. Maybe it has something to do with the memory upgrade/decoder mod. Maybe sometime you can load one of those diagnostic programs into your multi-cart and check, wether yours is crashing too.

[pser1]

Hello rolo,
Not an easy way to go with a Dragon 32 that has been upgraded to 64k if the ROM has not been upgraded too.
Don't need to waste time about the 64k (second ROM) if you don't intend to go 64K mode in BASIC mode.
But the standard 32K mode should be the same that it is in my Dragon64, in the contrary case, you cannot say you have a Dragon with 64Kb.
In fact my computer has 64k byte of RAM and so I can switch to map 1 (RAM mode) and get rid of the ROMS
Of course I need to copy the BASIC ROM to RAM because I need it (and the cartridges too)
So, you should download form the Archive the Dragon 64 ROM 1 (not the 64K version), burn it in a new EPROM and substitute the one on you upgraded Dragon32.
That will give you access to the 64K in RAM mode and my DSK will let you test the ROMs before burnig them on an EPROM.
If you have any problem with the downloading, just let me know and I will send and image of the standard D64 Rom to you
best wishes
Pere

[zephyr]

So, you should download form the Archive the Dragon 64 ROM 1 (not the 64K version), burn it in a new EPROM and substitute the one on you upgraded Dragon32.
That will give you access to the 64K in RAM mode and my DSK will let you test the ROMs before burnig them on an EPROM.
If you have any problem with the downloading, just let me know and I will send and image of the standard D64 Rom to you

The Dragon 32 is fitted with two 24-pin 4764 type (Texas Instruments TMS4764-35NL) ROM chips or equivalent. IIRC, a suitable EPROM replacement would be the Motorola MCM68764 or MCM68766.

[Rolo]

Part seven:

03-Nov-2013: modified another Tandy rom
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Katerpillar modDragon.rom

Katerpillar

(4 KiB) Downloaded 216 times

Finally solved. A tough one.
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Problem:
Dragon crashed when jumping from rom to ram, after copy-routine and did strange things.
After RESET Game could be manually launched in ram.
Solution:
Cartridge reduced to 4k.
New loader (removed unnecessary CoCo-checks and changed block copy (rom to ram)).
Reactivated interrupts at the right time.
Changed warm start vector (points at game) and enabled warm start.
Removed malicious TFR d,s, that changed stack

[Rolo]

Sorry, did not want to start a discussion about further upgrading my D32(64) in this thread . It's the wrong section. It just happend. Most of the time I don't need the upper bank. I could change SAM mode manually and copy parts of the rom. Yeah, maybe I should change the roms, but I want to read first, about any implications. Is down the list, at the moment. But if its just burning ready-prepared eprom-images and changing the components, then it's done in 30 minutes.

[Rolo]

The Dragon 32 is fitted with two 24-pin 4764 type (Texas Instruments TMS4764-35NL) ROM chips or equivalent. IIRC, a suitable EPROM replacement would be the Motorola MCM68764 or MCM68766.

And of course on my board, both are soldered in . Sockets must always have been very expensive... I've already abused my board when I upgraded to 64k. Do I really have to do that again? I'd probably go with a 27C128. I have plenty of them, they are pin compatible and I could burn in both versions, original and modified. I'd use a little switch to be able to fall back (bankswitch) to the original Dragon 32 mode, if necessary.

[pser1]

hello rolo,
I have a Dragon32 with the half good OKI 64k ram chips.
I made the few mods necessary to allow upper ram to be modified and then I tested write-read in a loop. It worked without problems.
I will not change the roms, because it keeps being a Dragon 32, I mean there is no serial port and its Basic is good enough (works for me). Yes, you loose the mode 48k but I dislike it because it kills the drive cartridge).
The extra memory can be used simply changing to map1 (ram map) (copying the ROMs to RAM if you still will need/use them) and you can use the last 8k (E000-FEFF) (16k if drives not used)
So, if you can work with the upper RAM when you need it, I agree not to make more hardware modification just to switch between two sets of ROMS.
By the way, mines are socketed but I will keep the original ones.
pere