Thread Like Summary
exidyboy, Osso, R. Belmont, Robbbert, robcfg, Xolod
Total Likes: 17
Original Post (Thread Starter)
#118997 04/17/2021 7:03 PM
by Xolod
Xolod
Gentlemen, I have several PCB, dump ROM, floppy disks and documentation for the LABTAM 3000 computer.
Perhaps there is someone who wants to implement it in MAME !?
https://www.dropbox.com/sh/v9n9l3r5a4ter91/AAB4xdb9URbhueiJAzuQlrJ-a?dl=0
Liked Replies
#120930 May 25th a 03:39 AM
by pmackinlay
pmackinlay
I've done some work on the Z80 SBC and believe I've found a plausible explanation for the 0x1800 firmware offset. According to the manual, all Z80 memory accesses pass through the address mapping logic, which maps logical to virtual addresses with a 2K page size granularity. The mapping logic supports 8 maps of 32 pages, and generates address bits 19..11 as well as RESB (resident bus vs Multibus access), MEM/IO and WP (write protect) signals. My theory is that during reset (and probably during interrupts) the mapping hardware is disabled, and its outputs are forced or float high. This has the effect that Z80 memory accesses during these cycles have address bits 15..11 driven high, and the other signals indicate resident bus, memory, read-only accesses (i.e. on-board EPROM). When combined with the initial mapping established by the firmware indicating EPROM #0 is decoded at 0xe000 on the resident bus, the result is the Z80 fetching logical address 0 from physical 0xf800, which is offset 0x1800 in the firmware.

Based on an initial implementation, it's now trying to access the floppy disk drive, so that's promising.
4 members like this
#119357 Jun 13th a 01:22 PM
by Just Desserts
Just Desserts
Looks like pin 25 (IR7) is hooked up to the MC6845 CRTC's vertical-sync pin.

I've got some video output, but it wasn't quite as exciting as I was hoping:

[Linked Image from i.imgur.com]
3 members like this
#119003 Apr 17th a 10:54 PM
by R. Belmont
R. Belmont
Interesting machine! Two 8086s and two Z80s and both the Intel and Zilog parts bins all over the place (plus a 6845 for video and a WD2797 FDC), and the technical manual seems to be OK. I don't have bandwidth right now to look at it, but maybe Duke or crazyc would be interested?
1 member likes this
#119023 Apr 20th a 06:41 PM
by Just Desserts
Just Desserts
Thanks. I'm a bit tired this evening, I've only had 3.5 hours of sleep, but I'll try to chip away at the driver over the course of the week, and then the weekend. There's a lot of hardware there, so getting everything "just right" might take a short while.
1 member likes this
#119042 Apr 26th a 12:19 PM
by Just Desserts
Just Desserts
Nothing really, the manual is very comprehensive.
1 member likes this
#119307 Jun 1st a 11:25 AM
by Just Desserts
Just Desserts
Not yet. Hasn't been submitted yet. It's on my list of things to do, ideally once I've wrapped up the Space Panic audio netlist, which should be this week.
1 member likes this
#119383 Jun 17th a 03:07 PM
by Xolod
Xolod
if there are any ideas, then I can look at the board for what is connected.
Also i can try put on the board of ICE Z80 https://github.com/hoglet67/AtomBusMon , I have it! And dumped all activity Z80.
1 member likes this
#119388 Jun 18th a 09:00 AM
by Just Desserts
Just Desserts
By the way, the reason for the 8086 VDU card freaking out is because of my flawed initial implementation: I had ROM mapped at both F0000 and 30000 so that the boot vector could be fetched.

I've switched to using a read tap which unmaps F0000-FFFFF as soon as the boot vector is fetched, and the VDU card now appears to be functioning more or less normally.

When the first vsync interrupt comes in, the VDU card looks at F8000 (which is located in the half-meg upper window into the Multibus address space). If it's zero, it simply sits in a tight loop, reading the location.

Since I had the boot ROM mapped in that range, it was seeing a non-zero value, then completely freaking out due to what would apparently be invalid data in that range.

So yes, at this point I suspect what's needed to move forward is to get the Z80 up and running.
1 member likes this
#119391 Jun 18th a 08:38 PM
by Xolod
Xolod
Originally Posted by Just Desserts
I actually have a crazy idea. It's not that the Z80 boots from address 0x1800, it's that it fetches from there.
in this case z80 ice will help. I am preparing a stand.
1 member likes this
#120370 Jan 14th a 08:42 AM
by Xolod
Xolod
Gentlemen, maybe in the new year who wants to continue working on LABTAM emulation?
If there is interest in this, then I can try to draw a circuit on PCB.
1 member likes this
#120923 May 20th a 05:30 AM
by Just Desserts
Just Desserts
By the way, Patrick, if you want to take on the base system itself, you're more than welcome. I just don't have the bandwidth or inclination to debug it at this point.
1 member likes this
#120921 May 20th a 04:02 AM
by pmackinlay
pmackinlay
Xolod, we now have a slightly more functional Multibus emulation in MAME, which should give a good base to get this system working. Can you please share some information about the system configuration with the 3232 card installed? Does the 3232 board fit in the same card cage that was used for the Z80 and 8086 boards? Does it work standalone, or does it require the Z80 and/or 8086 cards installed to make a working system? The datasheet indicated it has a SCSI device, but I don't see one on the board picture - does your system have anything connected to those ribbon cable connectors on the top edge of the 3232 board and/or can you verify if either or both of them are SCSI?

Is your unit the "desk top unit" mentioned in the manual, or some other configuration? Which slot is the 3232 board installed in?

Do you have any NS32000 software for the 3232 board aside from the firmware?
1 member likes this
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