Disassembly of the Z80 ROM of the C128

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Disassembly of the Z80 ROM of the C128

Ruud
Hallo allemaal,


Is there a disassmbly of the Z80 ROM of the C128, used to boot CP/M,
available? I don't know of one in E-format. I have one but on paper
and in German. So if there isn't one at all, I'm thinking of
creating one because I need it for a common project of the Dutch
Commodore club.

Many thanks in advance!


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Re: Disassembly of the Z80 ROM of the C128

Marko Mäkelä
On Sat, Feb 25, 2017 at 12:58:06PM +0100, [hidden email] wrote:
>Is there a disassmbly of the Z80 ROM of the C128, used to boot CP/M,
>available?

Actually the whole C128 boots up with the Z80. If I remember correctly,
the Z80 is checking the C= key and the -GAME and -EXROM inputs of the
MMU, deciding whether to switch to the C64 mode. Another (redundant)
check is done by the 8502. I happen to know this, because I made some
minor tweak to my C128 startup. I cannot remember what that tweak was,
but I guess that I could dump the ROM to find out.

        Marko

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Re: Disassembly of the Z80 ROM of the C128

David Wood-2
Zimmers does have the 4k z80 bios as a separate image in the firmware directory.

I thought the z80 source was in the wild, but I guess I'm mistaken.  Perhaps it's hiding on one of thte cp/m disks?

At any rate, the z80 bios is here:  http://www.zimmers.net/anonftp/pub/cbm/firmware/computers/c128/z80bios.bin

On Sat, Feb 25, 2017 at 8:38 AM, Marko Mäkelä <[hidden email]> wrote:
On Sat, Feb 25, 2017 at 12:58:06PM +0100, [hidden email] wrote:
Is there a disassmbly of the Z80 ROM of the C128, used to boot CP/M, available?

Actually the whole C128 boots up with the Z80. If I remember correctly, the Z80 is checking the C= key and the -GAME and -EXROM inputs of the MMU, deciding whether to switch to the C64 mode. Another (redundant) check is done by the 8502. I happen to know this, because I made some minor tweak to my C128 startup. I cannot remember what that tweak was, but I guess that I could dump the ROM to find out.

        Marko


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Re: Disassembly of the Z80 ROM of the C128

Marko Mäkelä
On Sat, Feb 25, 2017 at 10:00:43AM -0500, David Wood wrote:
>Zimmers does have the 4k z80 bios as a separate image in the firmware
>directory.

That file existed already on the FUNET archive that was maintained by me
and later moved to Zimmers.

>I thought the z80 source was in the wild, but I guess I'm mistaken.

I have not seen any source code, but I have not really looked for it.

I vaguely remember that my modification was simply to prevent the C128
from switching to C64 mode when -GAME or -EXROM is asserted on the
cartridge port. This would allow me to leave a C64 cartridge connected
all the time, and I could decide myself whether to switch to C64 mode,
by holding the C= key. For that simple modification, I did not have to
disassemble much of the Z80 BIOS, because the Z80 does not do much more
than check the signals from the MMU GPIO pins, and then switch to the
8502 processor.

If this was the case, the modification probably consisted of zeroing
some bits in the ROM, in the immediate operand of the bitwise-and
operation with the MMU register, so that the condition would never hold.

        Marko

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Re: Disassembly of the Z80 ROM of the C128

Ruud
In reply to this post by Ruud
Hallo allemaal,
 
 
> I have one but on paper and in German.

I know I should have it. But I cannot find it anymore. I know where
it should be found according my database but it simply isn't there.
I could have misplaced it in time but I doubt that.

Anyway, if anyone of you just happens to have the book 'C128 ROM
Listing' from Markt&Technik, you could do me a favour by scanning
the ROM listing of the Z80 part.

Many thanks in advance!


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Re: Disassembly of the Z80 ROM of the C128

smf
In reply to this post by David Wood-2
According to bill herds talks the z80 boot rom was hand assembled by the
wife of the cpm developer, because they needed it urgently and he was
out at the time.


On 25/02/2017 15:00, David Wood wrote:
> I thought the z80 source was in the wild, but I guess I'm mistaken.
> Perhaps it's hiding on one of thte cp/m disks?
>


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Re: Disassembly of the Z80 ROM of the C128

Ruud
In reply to this post by Ruud
Hallo allemaal,


> Anyway, if anyone of you just happens to have the book 'C128 ROM
> Listing' from Markt&Technik,...

Forget about it, I found it. That is, not the book but its PDF. It
seems I simply forgot to clear it from my database once scanned.

But it seems my troubles still aren't over yet: this book did not
contain the listing :(  (and I was so sure about it)
The Data Becker book only contains the very first part of the
listing so it can be that I mistook it foor being the whole listing
there.
To be continued....


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www.Baltissen.org







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Re: Disassembly of the Z80 ROM of the C128

Ruud
Hallo allemaal,


> To be continued....

Found it! It can be found in "Das CP/M Buch" from Data Becker. Just
found it when reading the indexes of various other possible
candidate-books. If interested, it is a 9 MB PDF.


--
   
Kind regards / Met vriendelijke groet, Ruud Baltissen
www.Baltissen.org







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Re: Disassembly of the Z80 ROM of the C128

Travis Fisher
In reply to this post by smf
I had seen one story about the CPM developer Von Ertwine being a badass hacker, funny that his wife was similarly inclined.  

This happened on the night before the CES show presenting the Commodore 128, from Bil Herd's posting:

"The next day we meet up with the guy who developed CPM (Von) for the C128.
As I mentioned earlier, someone forgot to tell him about the silly little ramifications of an 8563 bug. His 'puter didn't do it as he had stopped upgrading 8563s on his development machine somewhere around Rev 4 and the problem appeared somewhere around Rev 6. As Von didn't carry all the
machinery to do a CPM rebuild to fix the bug in software, it looked like CPM
might not be showable. One third of the booth's design and advertising was
based on showing CPM. In TRUE Animal fashion Von sat down with a disk editor
and found every occurrence of bad writes to the 8563 and hand patched them.
Bear in mind that CPM is stored with the bytes backwards in sectors that are
stored themselves in reverse order. Also bear in mind that he could neither
increase or decrease the number of instructions, he could only exchange them for different ones. Did I mention hand calculating the new checksums for the sectors? All this with a Disk Editor. I was impressed."

On Feb 27, 2017 3:46 AM, "smf" <[hidden email]> wrote:
According to bill herds talks the z80 boot rom was hand assembled by the wife of the cpm developer, because they needed it urgently and he was out at the time.


On 25/02/2017 15:00, David Wood wrote:
I thought the z80 source was in the wild, but I guess I'm mistaken.
Perhaps it's hiding on one of thte cp/m disks?



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Re: Disassembly of the Z80 ROM of the C128

smf
I only heard it recently.

https://www.youtube.com/watch?v=cwr8tTFGZtI&feature=youtu.be&t=2481

He gave a similar talk a few months earlier where he mentions the call,
but doesn't go into enough detail to figure out who wrote the code.

https://youtu.be/-Zpv6u5vCJ4?t=3275



On 27/02/2017 11:00, Travis Fisher wrote:
> I had seen one story about the CPM developer Von Ertwine being a badass
> hacker, funny that his wife was similarly inclined.
>


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Re: Disassembly of the Z80 ROM of the C128

geneb
In reply to this post by smf
On Mon, 27 Feb 2017, smf wrote:

> According to bill herds talks the z80 boot rom was hand assembled by the wife
> of the cpm developer, because they needed it urgently and he was out at the
> time.
>
Not the ROM, but the BIOS.

g.

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Re: Disassembly of the Z80 ROM of the C128

smf
On 27/02/2017 14:43, geneb wrote:

> On Mon, 27 Feb 2017, smf wrote:
>
>> According to bill herds talks the z80 boot rom was hand assembled by
>> the wife of the cpm developer, because they needed it urgently and he
>> was out at the time.
>>
> Not the ROM, but the BIOS.

What do you mean?


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RE: Disassembly of the Z80 ROM of the C128

Baltissen, GJPAA (Ruud)
>> Not the ROM, but the BIOS.
>
> What do you mean?

The BIOS of CP/M is not the same thing as the BIOS of a PC. The BIOS is the first part of CP/M that is loaded from disk and that is (should be) the only part of CP/M that is machine independent. As soon the BIOS is loaded the ROM is removed from the memory range and replaced by RAM. So the most important (and last) task of the ROM of a CP/M computer is loading this BIOS.

What IBM did was using the idea of a BIOS but implemented it in ROM and called this particular ROM the BIOS. So the BIOS of a PC and the BIOS of CP/M (should) do exactly the same but have been implemented in a different way.


Met vriendelijke groet / With kind regards,
Ruud Baltissen

www.Baltissen.org



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Re: Disassembly of the Z80 ROM of the C128

Gerrit Heitsch
On 02/28/2017 01:32 PM, Baltissen, GJPAA (Ruud) wrote:
>>> Not the ROM, but the BIOS.
>>
>> What do you mean?
>
> The BIOS of CP/M is not the same thing as the BIOS of a PC. The BIOS is the first part of CP/M that is loaded from disk and that is (should be) the only part of CP/M that is machine independent.

I think you mean 'machine dependant'.

  Gerrit



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FW: Disassembly of the Z80 ROM of the C128

Baltissen, GJPAA (Ruud)
Oops, indeed: 'machine dependant'.

Thank you for the correction!


Met vriendelijke groet / With kind regards,
Ruud Baltissen

www.Baltissen.org





-----Oorspronkelijk bericht-----
Van: [hidden email] [mailto:[hidden email]] Namens Gerrit Heitsch
Verzonden: dinsdag 28 februari 2017 14:32
Aan: [hidden email]
Onderwerp: Re: Disassembly of the Z80 ROM of the C128

On 02/28/2017 01:32 PM, Baltissen, GJPAA (Ruud) wrote:
>>> Not the ROM, but the BIOS.
>>
>> What do you mean?
>
> The BIOS of CP/M is not the same thing as the BIOS of a PC. The BIOS is the first part of CP/M that is loaded from disk and that is (should be) the only part of CP/M that is machine independent.

I think you mean 'machine dependant'.

  Gerrit



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Re: Disassembly of the Z80 ROM of the C128

smf
In reply to this post by Baltissen, GJPAA (Ruud)
I know, that doesn't help explain that comment.

The phone conversation between bil and the wife of the CPM developer was
definitely about the Z80 boot rom and not the BIOS as the BIOS in CPM is
loaded from disk. The BIOS was the code that was hacked at CES to work
round the 8563 bugs.


On 28/02/2017 12:32, Baltissen, GJPAA (Ruud) wrote:

>>> Not the ROM, but the BIOS.
>> What do you mean?
> The BIOS of CP/M is not the same thing as the BIOS of a PC. The BIOS is the first part of CP/M that is loaded from disk and that is (should be) the only part of CP/M that is machine independent. As soon the BIOS is loaded the ROM is removed from the memory range and replaced by RAM. So the most important (and last) task of the ROM of a CP/M computer is loading this BIOS.
>
> What IBM did was using the idea of a BIOS but implemented it in ROM and called this particular ROM the BIOS. So the BIOS of a PC and the BIOS of CP/M (should) do exactly the same but have been implemented in a different way.
>
>
> Met vriendelijke groet / With kind regards,
> Ruud Baltissen
>
> www.Baltissen.org
>
>
>
> De informatie in dit e-mailbericht is vertrouwelijk en uitsluitend bestemd voor de
> geadresseerde. Wanneer u dit bericht per abuis ontvangt, verzoeken wij u contact op te
> nemen met de afzender per kerende e-mail. Verder verzoeken wij u in dat geval dit
> e-mailbericht te vernietigen en de inhoud ervan aan niemand openbaar te maken.
> Wij aanvaarden geen aansprakelijkheid voor onjuiste, onvolledige dan wel ontijdige
> overbrenging van de inhoud van een verzonden e-mailbericht, noch voor daarbij
> overgebrachte virussen.
>
> APG Groep N.V. is gevestigd te Heerlen en is ingeschreven in het
> handelsregister van de Kamer van Koophandel Limburg onder nummer 14099617
>
>
> The information contained in this e-mail is confidential and may be privileged.
> It may be read, copied and used only by the intended recipient.
> If you have received it in error, please contact the sender immediately by
> return e-mail; please delete in this case the e-mail and do not disclose its
> contents to any person. We don't accept liability for any errors, omissions,
> delays of receipt or viruses in the contents of this message which arise as a
> result of e-mail transmission.
>
> APG Groep N.V. is registered in the trade register of the Chamber
> of Commerce Limburg, The Netherlands, registration number: 14099617
> 1�,j�j���a�����^q��i��ɚ�X��X�t===


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Re: Disassembly of the Z80 ROM of the C128

geneb
In reply to this post by smf
On Tue, 28 Feb 2017, smf wrote:

> On 27/02/2017 14:43, geneb wrote:
>
>> On Mon, 27 Feb 2017, smf wrote:
>>
>>> According to bill herds talks the z80 boot rom was hand assembled by the
>>> wife of the cpm developer, because they needed it urgently and he was out
>>> at the time.
>>>
>> Not the ROM, but the BIOS.
>
> What do you mean?

Patches that were done were applied to the BIOS, not the ROM.  Keep in
mind that under CP/M, the BIOS is loaded off of disk and isn't
ROM-resident.  CP/M is kind of a stack.  The BDOS, the BIOS, and the CCP.
The BDOS is the same for every CP/M system.  The BIOS is modified to match
the hardware that CP/M is running on, and the CCP is basically equivalent
to COMMAND.COM in DOS - it's transient.

g.


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Re: Disassembly of the Z80 ROM of the C128

geneb
In reply to this post by smf
On Tue, 28 Feb 2017, smf wrote:

> I know, that doesn't help explain that comment.
>
> The phone conversation between bil and the wife of the CPM developer was
> definitely about the Z80 boot rom and not the BIOS as the BIOS in CPM is
> loaded from disk. The BIOS was the code that was hacked at CES to work round
> the 8563 bugs.
>
The changes were made to the BIOS, not the boot ROM.

g.

--
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http://www.diy-cockpits.org/coll - Go Collimated or Go Home.
Some people collect things for a hobby.  Geeks collect hobbies.

ScarletDME - The red hot Data Management Environment
A Multi-Value database for the masses, not the classes.
http://scarlet.deltasoft.com - Get it _today_!

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back to cbm hackers

earth1dome1
Hi all. Got one of my email accounts back and it had about 20K full of
messages again. Hope to hear more from all f you.


Jeremy aka Weirdwolf back again. :)

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Re: Disassembly of the Z80 ROM of the C128

smf
In reply to this post by geneb


On 28/02/2017 15:06, geneb wrote:
>
> Patches that were done were applied to the BIOS, not the ROM. Keep in
> mind that under CP/M, the BIOS is loaded off of disk and isn't
> ROM-resident.  CP/M is kind of a stack.  The BDOS, the BIOS, and the
> CCP. The BDOS is the same for every CP/M system.  The BIOS is modified
> to match the hardware that CP/M is running on, and the CCP is
> basically equivalent to COMMAND.COM in DOS - it's transient.

The phone call was about the boot ROM for the Z80, that worked out
whether to go into C64 mode or C128 mode. Before that call the 6502
started first & it tried to handle the mode switch, but that caused a
problem with the magic voice cartridge.

It had nothing to do with CPM.


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