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+--- Thread: New Model Development Updates (/thread-449.html)
RE: New Model Development Updates - MbeeTech - 14-03-2025
New photos from setup time and the Train and Hobby Show on at Sandown (Vic) this weekend.
RE: New Model Development Updates - paulmackay - 26-03-2025
(11-01-2025, 01:08 PM)MbeeTech Wrote: The PCB for the model in the 256TC case has just been completed.
It is essentially the same circuit, but with the keyboard section removed, a LED board added and some
extra mounting holes to fit it in the case with.
Here's a preview :
The LED board breaks out from the main board & is connected by a small cable to the back of the 98 key keyboard.
cannot wait to purchase one..... getting excited
RE: New Model Development Updates - MbeeTech - 16-04-2025
Hi All.
Time for another update.
Firstly, the first batch of the production key caps for the 98 key model are finally in.
As you will see from the photo, the colours have changed to better align with the ABS case.
They are a little darker than the case on purpose, and the blue keys have been toned down a little.
Much happier with the look compared to the prototype set that had white keys.
The white was too stark for the beige case.
Hopefully you'll agree.
The last few weeks have been spent on getting the Z80 to work at 20Mhz rather than the 10Mhz of the initial spec.
I didn't consider 20Mhz initially as the Z80PIO was only ever made as a maximum 10Mhz part (Z84C2010PEC/G),
however, the Z80CPU was made to a max frequency of 20Mhz (Z84C0020PEC/G).
I really wanted to be able to run the Z80 at 20Mhz because the new 4 bit-plane graphics modes require a lot more data to be
moved around (4 times the data, + palette information etc.) and I didn't want it to be ' pretty but slow '.
So, I came up with a scheme whereby the PIO could still be clocked at 10Mhz, with some logic in place, while the CPU
was running at 20Mhz.
I had to cater for all accesses to the PIO to have wait states (if the CPU was running at 20Mhz) and
also detection of the interrupt acknowledge cycle (M1 & IORQ active), and also the bus snooping that the PIO does to detect
a return from interrupt instruction that clears it's internal interrupt logic tree.
Aside from the PIO clocking adjustments, the main Z80 system ram and 'Boot ram' have been changed to faster speed parts
along with the HCT245, HCT541 & HCT32 parts changed to AHCT equivalents for smaller propagation delays to meet the 20Mhz
CPU's timing requirements.
Running at 20Mhz came up as expected, but initially it would hang on disk activity. It took me a week of diagnosis to find out that
the emulation code (that the 68SZ328 runs for Floppy disk <-> SDcard handling) needed a tweak.
When the Z80 reads or writes the floppy disk ports the Z80 is immediately held in a BUSREQ/ACK state while the emulation code
on the 68SZ328 figures out what needs handling.
Logic inside the FPGA automatically starts the BUSREQ hold of the Z80 when a FDC port access happens, then this also triggers
an interrupt for the 68SZ328 to handle the emulation processing.
After the processing is done, the 68SZ328 then resets the BUSREQ hold and enables the Z80 to continue running.
The problem was that I was enabling the Z80 to run again before resetting the interrupt register so when the Z80 was running at 20Mhz, it would
fire off another FDC port access before the 68SZ328 was ready for another interrupt, so it would be missed.
This wasn't a problem running at 10Mhz as the 68SZ328's interrupt was reset before another Z80 FDC access was ever made.
At 20Mhz though, the Z80 got in again too quick.
After changing the code around so that the interrupt was cleared before enabling the Z80 to run again all came good.
In all of this work, I also found that the WD2793 disk controller also needed wait states to meet timing even at 10Mhz, so that was
added as well.
Long story short, our new models now run at either 3.375Mhz, 10Mhz, or 20Mhz.
RE: New Model Development Updates - Mr Lurch - 16-04-2025
Very cool!
RE: New Model Development Updates - someone - 18-04-2025
Illuminated keycap legends with dynamic fade out would be a really cool upgrade.
Any chance of bumping it up to 50MHz with an eZ80?
Have a safe Happy Easter!
RE: New Model Development Updates - RedskullDC - 19-04-2025
Just waiting for you to say that orders are open Ewan!
Take our $$$$
Cheers,
Leslie
RE: New Model Development Updates - MbeeTech - 20-04-2025
(18-04-2025, 12:38 PM)someone Wrote: Any chance of bumping it up to 50MHz with an eZ80?
Actually no. I have investigated the eZ80 for Microbee suitability and the big stumbling block is that
the internal peripherals are mapped in permanently at I/O Ports 00h->FFh. There is no way to disable them
or relocate them, making is impossible to use with a standard Microbee Port Map.
The Z8S180 on the other hand has internal peripherals / control registers that can be mapped out of the way.
So, the top speed for a Microbee (with actual silicon Z80) is the Z8S180's 33Mhz.
Happy Easter to all. :-)
RE: New Model Development Updates - MbeeTech - 20-04-2025
(19-04-2025, 04:38 PM)RedskullDC Wrote: Just waiting for you to say that orders are open Ewan!
Take our $$$$
Cheers,
Leslie
Hey Leslie.
Great to hear from you.
Still a little bit to tick off, then will send them out to a few Beta testers to give them a good shake down.
I'll post more about the Beta test phase and how people can get involved when just about ready to go.
RE: New Model Development Updates - RetroBee - 02-05-2025
Hi Ewan,
Hope you're going well.
You mentioned in a previous post -
"Hardware Cursor / Sprite implemented.
Now there are three layers to the Microbee Screen Display :
Background : 4 plane graphics
Foreground : Regular text & semi-graphics (re-programmable FONT gives basic PCG style characters)
Hardware Sprite / Cursor with transparency control (pixels with assigned colour zero do not appear / show content from Foreground / Background)
Hardware Cursor up to 64 pixels wide x 32 pixels high with 16 colours (15 + transparent) from any of the 16 foreground palettes."
Any chance you can include more 'hardware sprite' support ie) 8 at least? I know we have the new Microbee running at 20MHz but it will take pressure off the CPU. I really want to use this for 2D game development for lots of moving and colourful sprites on the screen. This would go a long way.
Cheers,
RetroBee
RE: New Model Development Updates - MbeeTech - 02-05-2025
(02-05-2025, 04:35 PM)RetroBee Wrote: Any chance you can include more 'hardware sprite' support ie) 8 at least? I know we have the new Microbee running at 20MHz but it will take pressure off the CPU. I really want to use this for 2D game development for lots of moving and colourful sprites on the screen. This would go a long way.
Cheers,
RetroBee
It is on the wish list.
Whether more sprites are implemented prior to release is yet to be determined.
It would certainly be nice to have more, but at some point I just have to just get the machines into production.
The benefit of having the screen section implemented in the FPGA is that I can just do a firmware update to include
new stuff like more sprites.
Thanks for the suggestion.