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+--- Thread: Worthwhile optional upgrades? [Premium Series] (/thread-466.html)
Worthwhile optional upgrades? [Premium Series] - Snuffytime - 20-04-2022
I was fortunate enough to recently obtain one of my "Holy Grail" machines - a Premium Series PC85 colour 'Bee which I want to upgrade to add mass storage. But there are some other possible options such as expanding the attribute/PCG RAM to 32k, adding the SN76489AN and amplifier, and adding the RTC. Which of these are worthwhile? That is, is there much existing software which takes advantage of any of these upgrades?
RE: Worthwhile optional upgrades? [Premium Series] - MbeeTech - 20-04-2022
(20-04-2022, 03:56 PM)Snuffytime Wrote: I was fortunate enough to recently obtain one of my "Holy Grail" machines - a Premium Series PC85 colour 'Bee which I want to upgrade to add mass storage. But there are some other possible options such as expanding the attribute/PCG RAM to 32k, adding the SN76489AN and amplifier, and adding the RTC. Which of these are worthwhile? That is, is there much existing software which takes advantage of any of these upgrades?
Hi Snuffytime.
>Attribute ram / 32k PCG
While it is possible to upgrade the video memory the only software I know of that uses the expanded ram is user created.
By that I mean, I've not seen any commercial software take advantage of expanded video memory.
Here's why :
* expanding the Screen / Colour / Attribute ram from 2K to 8K static rams theoretically gives you video 'Pages', however,
in practice there were some unwanted side effects making the machine unusable.
* 32K of PCG was a good option, but a very low percentage (next to none) came out of the factory that way so there was
little incentive to write software to make use of it (very limited market)
* 64 x 16 screen mode was fully catered for with 8 banks of PCG which was the most common video mode software was
written for. 80 x 24 screen mode would need the extra banks if a full bit mapped display was to be utilized, but word processors
(Simply Write) and comms packages (Telcom) were the most common 80 x 24 / 80 x 25 screen mode programs and didn't
need the additional graphics ram.
The Premium Plus upgrade (which might be a good way to add mass storage to your Premium -
http://www.microbeetechnology.com.au/store/premium-to-premium-plus-upgrade.html ) does upgrade the PCG Ram
to 32k and eventually I would like to provide another graphics mode for basic (HIRES / HIRES2 / <HIRES3>) which would give
640 x 256 fully dot addressable graphics. The scheme uses 10 PCG banks and it is something that will be implemented for the
up-coming Classic-Plus kit.
>RTC / SN76489
The system software does support the real time clock if it is fitted, but will need an update for 2000 Century to be usable.
There is no [commercial] software support for the SN76489 in the bee, so it would only be of interest if you wanted to write
your own routines to use it.
RE: Worthwhile optional upgrades? [Premium Series] - ChickenMan - 20-04-2022
As ejwords said, basically the only worthwhile option is to add in some games in the top 1/2 of the roms after replacing the 2764 eproms with 27128 eproms. We have provided a few more games in ROM form suitable in the Repository. All working well on my PC85. See https://microbeetechnology.com.au/forum/showthread.php?tid=366 for further information, though that was for a Standard PC85 but still applies to the Premium PC85.
RE: Worthwhile optional upgrades? [Premium Series] - someone - 20-04-2022
Hi Snuffytime!
Someone's glad you've got an interest with upgrades.
Someone has some super dooper Alpha plus machines and can tell you a few stories as to why the Premium Series ended up the way did.
1. The Alpha Plus prototypes were designed for "Skinny DIP" 0.3 inch wide 6116 and 6264 RAMs.
Even at the development stage, the 6264 Skinny DIP RAMs were scarce thus the prototype PCBs were modded to accommodate the standard 0.6 inch wide packaging.
The supply problems carried on through to production leaving only room for 2 6264s (instead of the intended 4).
2. The 2K/8K Char/Attr/Colour RAM debacle came because of a stupid design decision that when 2K RAMs were fitted its PCB mods applied ignored current APLUS latch bank setting. (i.e. Bank#0 was permanently mapped).
With that being the case software was written with this incorrect behaviour in mind.
If you want, you can implement a switch between the behaviours.
3. There is software available for the SN76489 PSG (Programmable Sound Generator) but as Ewan said not commercially. (Someone's got a jukebox app that plays a selection of songs). The logical choice was use the AY-3-8912 PCG because the existing BeeThoven software could be leveraged but
the Alpha Plus PCB did not have enough room to accommodate it because it was a 0.6inch wide DIP package so the smaller SN76489 PSG was used.
4. The Alpha Plus has a wonderful 320/256 x 256 (Viatel variant) display mode that is great for video games and colour based applications.
In conjunction with a non production implemented PCB mod, an Alpha Plus can display 8x8 characters with 100% efficiency of the PCG RAM.
Running an Alpha Plus in 256 x 256 mode improves bit map graphics by simplifying and speeding up graphics calculations.
It makes it great to run ZX Spectrum, Apple ][, MSX and arcade software ports.
With that said, there are more mods such as pixel byte flippers, improved colour modes and multi read/write.
As for mass storage to work with a ROM based machine without the need for implementing a disk controller, and if you're feeling game, why not implement a FTDI VDrive/VMusic module? You can attach this to the parallel port and plug in your own supporting NET ROM.
From it you can save and store files to USB memory sticks as easy as NET SAVE "filename.mwb" and NET LOAD "filename.mwb"
If you've got a Disk based system and you feel like a challenge, configure an ARM based microcontroller to fit into the FDC socket to read and write to SDCards, USB sticks and alike without the Floppy disk performance retarding seeks and transfer rates. This solution has the advantaged of using the standard BOOT ROM.
Have a great day!