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CP/M-80 Z80 Emulator Bug

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Hugh Redelmeier

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Nov 10, 1986, 6:01:24 PM11/10/86
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I have just spent some time putting up the CP/M-80 emulator on my
1040ST. I have found the emulator seems quite well done. But there
are some problems with it.

In the Z80, there are two flags for purposes of BCD arithmetic: the
H flag is for recording "half-carry" and the N flag is for recording
whether the last operation was an add or a subtract. An AND
instruction sets both N and H flags. Similarly, an OR instruction
clears both. (In the 8080, there is no N flag, and both the AND and
OR instructions clear H.)

In the emulator, the AND and OR instructions seem to leave the N and
H flags alone. So it does not match the Z80, or even the 8080.
Although this seems unimportant, I only discovered it because it
caused the program that I was porting to fail.


The emulator seems to support only floppy drives. I could not get
it to use a RAM disk (I use the Intersect RAM disk at the moment).
Since the disks it uses must have a CP/M file system, I don't wish
to try my hard disk. Even on a floppy, it only supports a single
side! This makes the emulator much less useful on a system with
only one floppy drive.

The make_cpm command (to start the bootstrapping process of creating
the first CP/M disk) prompts at the start. DO NOT put the blank
disk in at this point. It needs to fetch a file from the TOS disk
(which must be on a floppy, I think). Put the blank disk in at the
second prompt. If you do put in a blank disk the first time, you
will not get a diagnostic. The machine will just fall asleep for a
minute and then return to the desktop.

I sure wish that the TOSCPM and CPMTOS commands (for transferring
files between TOS and CP/M file systems) would take ambiguous file
names. As it is, a command must be issued for every file
transferred.

I don't see a way to change what terminal the console emulates. My
ST is replacing a Kaypro II. But since the Kaypro emulates an ADM-3
(more or less) and the ST emulates a VT52 (more or less), I cannot
trivially move my programs. (Legality is another problem, but I am
not talking about copyrighted programs.)

The emulator is not quite good enough to be useful to me. Just a
few enhancements could change this.

Now that this program is free, I wonder how much support will be
provided by Atari or the original developer (a company in West
Germany).

Hugh Redelmeier (416) 922-1937
utzoo!hcr!hugh

pe...@utcsscb.uucp

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Nov 12, 1986, 11:05:54 AM11/12/86
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In article <14...@hcrvx1.UUCP> hu...@hcrvx1.UUCP writes:
>I have just spent some time putting up the CP/M-80 emulator on my
>1040ST. I have found the emulator seems quite well done. But there
>are some problems with it.
>
>The emulator seems to support only floppy drives. I could not get
>it to use a RAM disk (I use the Intersect RAM disk at the moment).
>Since the disks it uses must have a CP/M file system, I don't wish
>to try my hard disk. Even on a floppy, it only supports a single
>side! This makes the emulator much less useful on a system with
>only one floppy drive.

I have had no problems with running the emulator off of a
ramdisk. Using the inidir.com program included in the package, I
have been able to reinitialize ram disks previously set up under
TOS for CPM. The ramdisk I am using is one I downloaded off of a
local BBS, and has no documentation, so I do not know which one it
is . It is a fixed 600k Ram disk.
In an in store experiment, I have tried running the emulator
off of 1 partition of the Atari 20mb Hard Drive, with seeming success.
(Just imagine: A system with Magic Sac, the CPM emulator and the ST, all
running off of different partitions of the same Hard disk!)

>The make_cpm command (to start the bootstrapping process of creating
>the first CP/M disk) prompts at the start. DO NOT put the blank
>disk in at this point. It needs to fetch a file from the TOS disk
>(which must be on a floppy, I think). Put the blank disk in at the
>second prompt. If you do put in a blank disk the first time, you
>will not get a diagnostic. The machine will just fall asleep for a
>minute and then return to the desktop.

Further advice. people with 1040st's should boot off of a
SINGLE SIDED diskette before attempting the installation program. This
seems to make a diffence.

>
>Hugh Redelmeier (416) 922-1937
>utzoo!hcr!hugh

------------------------------------------------------------------------

Pete Santangeli
pete@utcsscb@utcs
psantangei on BIX

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