ICL OPD

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tofro
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Re: ICL OPD

Postby tofro » Sat Aug 15, 2020 5:18 pm

RalfR wrote:I do not quit right remember but someone told me, that MDV handling on the Spectrum/IF 1 was hardware and on the QL it is software or vice versa.


That's not true. Microdrives on Spectrum/IF1 and QL basically work identically. It is true that the QL implements more software, because it supports non-sequential random access - But that's just a thicker software layer on top of the HW the Spectrum doesn't have.


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Re: ICL OPD

Postby janbredenbeek » Sat Aug 15, 2020 8:48 pm

RalfR wrote:I do not quit right remember but someone told me, that MDV handling on the Spectrum/IF 1 was hardware and on the QL it is software or vice versa. Would be interesting to know, how it is handled by OPD

AFAIK the write protect handling was in software on the Spectrum and in hardware on the QL. On the Spectrum, you could lose a cartridge's contents if a program went berserk and sent an ill-formed OUT instruction to the wrong port (in fact, a number of ports since the decoding used just two bits). On the QL, the hardware prevented writing to the cartridge but the software didn't know about that, so it retried several times before giving up with a 'bad or changed medium' message.
Don't know about the OPD though...


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Re: ICL OPD

Postby janbredenbeek » Sat Aug 15, 2020 9:02 pm

tofro wrote:That's not true. Microdrives on Spectrum/IF1 and QL basically work identically. It is true that the QL implements more software, because it supports non-sequential random access - But that's just a thicker software layer on top of the HW the Spectrum doesn't have.

The hardware is only different for the write protection mechanism (see previous post). Even the Spectrum supports random access (in a sense that it can scatter-load parts of a file - the physical access to the media is always sequential since it's a tape loop!) when using LOAD etc. The QL is more sophisticated in that most of the physical access is done under interrupts so normal processing can continue, albeit somewhat slower.


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Re: ICL OPD

Postby tofro » Sat Aug 15, 2020 11:43 pm

janbredenbeek wrote: Even the Spectrum supports random access (in a sense that it can scatter-load parts of a file - the physical access to the media is always sequential since it's a tape loop!) when using LOAD etc. The QL is more sophisticated in that most of the physical access is done under interrupts so normal processing can continue, albeit somewhat slower.


My mentioning of sequencial access only on the Spectrum:
The Spectrum doesn't have a concept of a user-modifiable file pointer - You cannot append to a file once it's closed, you can't write to a file you have opened for reading (that is, no "rw" mode) and you cannot access specific records in a file. That's probably more due to the limited amount of memory for buffers and the general limitations of the Spectrum ROM rather than the capabilities of the IF1.

Tobias


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Re: ICL OPD

Postby janbredenbeek » Sun Aug 16, 2020 12:42 am

tofro wrote:My mentioning of sequencial access only on the Spectrum:
The Spectrum doesn't have a concept of a user-modifiable file pointer - You cannot append to a file once it's closed, you can't write to a file you have opened for reading (that is, no "rw" mode) and you cannot access specific records in a file. That's probably more due to the limited amount of memory for buffers and the general limitations of the Spectrum ROM rather than the capabilities of the IF1.
Tobias

IIRC the Spectrum IF1 ROM did have a number of system calls (called 'hook codes' - essentially RST 8 instructions followed by a byte code, above the range used for ordinary error codes) that allowed a machine code program to access a data file randomly. That said, file handling was more limited compared to the QL - there was no OPEN_IN/OPEN_NEW, if the file opened did not exist on the medium it was simply opened for write, else for read. Also, it wasn't possible to read files written by SAVE in this way (which was a means of copy protection).


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Re: ICL OPD

Postby tofro » Sun Aug 16, 2020 1:27 am

janbredenbeek wrote:
tofro wrote:My mentioning of sequencial access only on the Spectrum:
The Spectrum doesn't have a concept of a user-modifiable file pointer - You cannot append to a file once it's closed, you can't write to a file you have opened for reading (that is, no "rw" mode) and you cannot access specific records in a file. That's probably more due to the limited amount of memory for buffers and the general limitations of the Spectrum ROM rather than the capabilities of the IF1.
Tobias

IIRC the Spectrum IF1 ROM did have a number of system calls (called 'hook codes' - essentially RST 8 instructions followed by a byte code, above the range used for ordinary error codes) that allowed a machine code program to access a data file randomly. That said, file handling was more limited compared to the QL - there was no OPEN_IN/OPEN_NEW, if the file opened did not exist on the medium it was simply opened for write, else for read. Also, it wasn't possible to read files written by SAVE in this way (which was a means of copy protection).


The IF ROM has a number of RST8 hook codes, yes (They're listed in the famous "ZX Microdrive Book"). But none for appending a file or positioning a file pointer. They are more or less resembling what BASIC could do. You could tell it to read or write a specific sector number on the drive, but that's obviously not what we'd call "random access" for files.


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Re: ICL OPD

Postby Pr0f » Sun Aug 16, 2020 9:29 am

tofro wrote:
Chr$ wrote:... The speech synthesis is fun but has a very limed vocab... so you can't make it say rude works :geek:


Now, that makes it entirely useless - Because what else you'd use it for :)


I think you could provide your own 'data' to produce the desired words.

As far as I know, there is no speech ROM on board, so the speech processing data must come from the ROMS in the 68K's address space.

the PDF for the speech chip is too large to upload, at 7.5MB


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Re: ICL OPD

Postby Chr$ » Sun Aug 16, 2020 11:08 am

Pr0f wrote:
As far as I know, there is no speech ROM on board


I was under the impression that there was a speech ROM installed.

A further ROM contains the vocabulary for the speech synthesiser.

(source: http://www.tebbo.com/archive/pw8412.htm)


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Re: ICL OPD

Postby RalfR » Sun Aug 16, 2020 12:03 pm

tofro wrote:They're listed in the famous "ZX Microdrive Book"
Is that the book from Jochen Merz? I remember that he has written a book of that.


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Re: ICL OPD

Postby RalfR » Sun Aug 16, 2020 12:31 pm

Chr$ wrote:But you could use the CUB with the OPD to test it out? That's 2 OPD's in Germany then at least, there can't be many.
When Tony Firshman has sent the OPD with a monitor to me, the monitor was totally destroyed, a slightly bad package. So I had to modify my CUB to test the OPD. All work as expected but I just used it for a few hours, then back in the cellar.

In retrospect it wasn't a good idea to modify the CUB.



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