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+--- Thread: Obscure Microbee Hardware Enhancements (/thread-34.html)
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RE: Obscure Microbee Hardware Enhancements - someone - 22-01-2020
Be aware that there is a microbee windowed environment for the Alpha Plus that supports colour. It had simple apps such as Clock, Calculator, Graphics Editor, Text Editor, Terminal, Disk File Explorer and CP/M window.
RE: Obscure Microbee Hardware Enhancements - MbeeTech - 22-01-2020
(22-01-2020, 09:04 AM)someone Wrote: Be aware that there is a microbee windowed environment for the Alpha Plus that supports colour. It had simple apps such as Clock, Calculator, Graphics Editor, Text Editor, Terminal, Disk File Explorer and CP/M window.
Hello Someone.
Was it software developed by Microbee?
I've not seen anything like that.
The closest I've seen was a program called Take-5 (incomplete) that was for the 'Telecomputer' that had clock, calendar, phone / modem dialing, terminal and calculator functions.
RE: Obscure Microbee Hardware Enhancements - someone - 16-02-2020
Here is the photo!
RE: Obscure Microbee Hardware Enhancements - ChickenMan - 16-02-2020
Take Five as referred to by Ewan.
RE: Obscure Microbee Hardware Enhancements - Ernest - 16-02-2020
(16-02-2020, 07:00 PM)someone Wrote: Here is the photo!I assume the above photo is of the Alpha Plus Prototype as it looks like a MB1248 Mainboard with a MB1732 SRAM coreboard with no EPROM software, with an expansion board in the 50 way expansion port where I assume the firmware resides.
Do you have a circuit diagram for the 50 way development board?
Is this the platform that the "microbee windowed environment for the Alpha Plus that supports colour" was developed on?
Ernest
RE: Obscure Microbee Hardware Enhancements - someone - 23-02-2020
(16-02-2020, 07:59 PM)Ernest Wrote:(16-02-2020, 07:00 PM)someone Wrote: Here is the photo!I assume the above photo is of the Alpha Plus Prototype as it looks like a MB1248 Mainboard with a MB1732 SRAM coreboard with no EPROM software, with an expansion board in the 50 way expansion port where I assume the firmware resides.
Do you have a circuit diagram for the 50 way development board?
Is this the platform that the "microbee windowed environment for the Alpha Plus that supports colour" was developed on?
Ernest
Hi Ernest,
Sorry for the late response because someone hasn't logged in recently and didn't subscribe to this thread.
The photo is just of an standard Alpha machine. (However it is modified with a simplistic screen flicker reduction circuit that consists of a 74LS00 placed into the "SPARE" socket and wired in. The screen flicker of a standard microbee drives someone nuts.) You're right about the coreboard having no EPROMS but if you look carefully at the bottom left of the coreboard you will notice 3 production masked ROMS.
The photo shows 3 50 way expansion boards. Which one would you like the circuit diagram? They can be concurrently plugged in if given the right 50 way cable and power supply requirements.
If you plan to build one now there'd be some component substitutions to reduce the part count and complexity.
No, the microbee in the photo is not the Alpha Plus in which the windowed environment was developed. The Alpha plus prototypes had no solder mask and contained a rat's nest of wires to counter the PCB layout mistakes and mods.
Cheers
Someone
P.S. Someone is always blamed for something!
RE: Obscure Microbee Hardware Enhancements - Ernest - 23-02-2020
(23-02-2020, 01:03 PM)someone Wrote:(16-02-2020, 07:59 PM)Ernest Wrote:(16-02-2020, 07:00 PM)someone Wrote: Here is the photo!
Hi Ernest,
Sorry for the late response because someone hasn't logged in recently and didn't subscribe to this thread.
The photo is just of an standard Alpha machine. (However it is modified with a simplistic screen flicker reduction circuit that consists of a 74LS00 placed into the "SPARE" socket and wired in. The screen flicker of a standard microbee drives someone nuts.) You're right about the coreboard having no EPROMS but if you look carefully at the bottom left of the coreboard you will notice 3 production masked ROMS.
The photo shows 3 50 way expansion boards. Which one would you like the circuit diagram? They can be concurrently plugged in if given the right 50 way cable and power supply requirements.
If you plan to build one now there'd be some component substitutions to reduce the part count and complexity.
No, the microbee in the photo is not the Alpha Plus in which the windowed environment was developed. The Alpha plus prototypes had no solder mask and contained a rat's nest of wires to counter the PCB layout mistakes and mods.
Cheers
Someone
P.S. Someone is always blamed for something!
Thanks Someone for the clarification,
I thought it would take some funky design to do it off board via the 50 way.
I agree with you on the screen flicker, have modified a number of units myself based on the deglitch circuit introduced on the later Alpha machines. I assume you are restricting the RAM writes to the video retrace period.
The resolution in my browsing was insufficient to distinguish between SRAM and Mask ROM.
I don't know the function of each of these adapter boards, but the CD card adapter has my curiosity piqued?
Now that Alpha plus prototype would have been an interesting photo.
P.S. Someone is always blamed for something! But then something is always, for someone-else to do
Best Regards Ernest
RE: Obscure Microbee Hardware Enhancements - someone - 24-02-2020
Thank Ernest,
The screen flicker mod on this bee only shortens the length of the flickers and does not impede the CPU allowing the CPU to run at full speed. It does it by allowing the 74LS166 Shift register to pump out its remain pixel contents onto the screen whilst the CPU is accessing the VDU/PCG RAM (unlike the original design which just clears its contents to black upon CPU access).
The SD Card interface makes use of the full speed SPI interface card (the 50way card to the left). The SPI interface has its own independent clock that can run at 20MHz.
This card was designed in 1985 as a mouse interface prior to the existence of the SPI moniker and subsequently adjusted to handle 3.3v peripherals such as SD Cards as needed.
The other little boards are SPI peripherals such as Serial UART, 8x 7 segment LED display and temperature sensor.
Access to the SPI devices is as easy as using MWBASIC with IN and OUT keywords.
The 50 way card on the right is the Roland MPU-401 MIDI interface. It was used to get the microbee to play drum machines and electronic synthesizers.
The large board in the centre is contains a Z80A DART, Z80A CTC, Z80A PIO, Baud rate generator, battery backed RTC, true RS232 level transmitters and receivers.
It was built prior to the design of the DRAM coreboard and was used to support split modem baud rates of 1200/75.
The CTC is extremely handy to as a time base and sound (tone) generator and interrupt controller.
RE: Obscure Microbee Hardware Enhancements - Ernest - 26-02-2020
Hi someone,
I am keen to know more about the SPI interface? That not only sounds like it was well ahead of it's time, so much so, it would make the Microbee suitable for development even in the current times.
More information please.
Ernest
RE: Obscure Microbee Hardware Enhancements - someone - 26-02-2020
Hi Ernest,
Back in the 1970's and 1980's it was deemed that a parallel interface was the way to go because one effectively could transfer data quicker that a single wire serial interface such as RS232.
However sending data in parallel at higher speeds is subject to synchronisation problems and now in the 21st century where back using serial interfaces where this is not an issue.
The mouse interface consisted of an 8 bit parallel bus DAC of that era but to make the interface use less wires all the data is sent through a shift register in exactly the same way as the video shift register of the microbee. In addition there is a Chip select line and separate clock line. For the mouse we're mainly just pumping data back from the DAC but with an additional transmit shift register we can also send it data/commands. To support multiple devices an additional device select flip flop is added.
These days the design can be squashed into a single IC, but back then it consisted of 12 LSI ICs.
Someone