bugeyedcreepy wrote: ↑Tue Jun 18, 2024 7:21 am
...See? My imagination only gets me in trouble...
Imagination is a good thing. Many great things have come to be, from great imaginative thoughts!
For now, a single combination CPU Card, catering for DIP / PLCC / 1MB ROM Expansion, will keep me busy routing traces for a while.
I decided to try going this
more difficult route, instead of just making a seperate PLCC only CPU Card.
It remains a CPU & Memory Card, which still aligns with the MECB Card
logical segmentation of function, but interestingly will expand nicely on the capabilities & function of the existing CPU Card.
Effectively, enhancing it with the ability to now either choose a DIP or PLCC packaged CPU, and either the existing 32KB DIL EEPROM or faster 512KB FLASH ROM chips (in PLCC package), and, also either 1 or 2 ROM’s for up to 1MB of switched bank-selected ROM (just like the existing
seperate ROM Expansion card).
In addition, you could also continue to use a DIP40 CPU and simply just swap out the existing 150ns 32KB DIP28 ROM for a single faster 70ns 64KB of PLCC32 FLASH ROM (without adding the bank-switching components). Thus, giving you full 64K Memory Map freedom, to mix up to 64KB RAM with up to 64KB ROM, and also potentially allowing faster overclock speeds (on the basis that the existing 150ns ROM is possibly the main speed limiting factor at the moment).
My vision for this new enhanced Card would then be a MECB 6809 CPU Card v3.0.
The only issue is that it is quite crowded, and will require me to go to a 4 layer PCB, which is more expensive.
So far, I have settled on the layout, I’m now just in the process of trying to route this busy creation!
Once done, I will have to decide whether to retire the existing CPU Card (as the enhanced v3.0 CPU Card will be backward compatible),
or, to offer both (on the basis that new 4 layer PCB will be a little more expensive than the original 2 layer PCB).
But, lots of routing challenges to solve first, before this vision becomes a reality (or I revert to the idea of a seperate PLCC only Card).
EDIT (3 days later)...
Life is a learning curve... So, after 2 days of PCB routing, when I was about 90% finished with my 4-layer
all-in-one combination PCB creation, I took a moment to check the ordering process for the first prototype PCB manufacture.
It was only then that I realised that the "little more expensive" 4 layer PCB, was actually going to cost me 4x (
four times!) the price of my usual 2-layer PCB's. Even at a higher production quantity, I was looking at 3x the PCB cost!
So, it then dawned on me that anybody obtaining the PCB (for their own build), would either be building a DIP CPU based system, or a PLCC CPU based system. Obviously not both!
So, from an end-user perspective there is no real advantage to a "all-in-one combination PCB" (to justify the increased cost!).
My desire to make one was purely from a simplified stocking / inventory point of view (and of course...
The Challenge!).
I'd then have just one PCB, to suit both DIP and PLCC build desires.
So, roll on the next day, and I've started-out again on a 2-layer PLCC only CPU Card. Still enabling the combination of CPU Card and ROM Expansion Cards, but no longer supporting a choice of either DIP or PLCC packages (for CPU & ROM).
This will mean a seperate 6309 PLCC CPU Card being added to the available MECB Cards (and the existing 6809 CPU Card will remain).
But, as I said, this does actually make more sense (from a user perspective), and the additional PCB option will be the same usual 2-layer PCB price.
So, I must now get back to my PCB Layout & Routing (starting again from square one).
In the meantime, I'll share below a 3D PCB render of what my 90% complete 4-layer all-in-one combination PCB looks like!
Pretty nice (
a work of art, if I do say so myself). But, for now, it will remain as a 90% complete project (on hold for now).
So, hopefully, in another couple of days, I'll eventually have a 2-layer PLCC PCB ready to submit for manufacture!
Then I can eventually get back to one of my other
in-waiting projects!
I'm totally gonna take that as a WIN!!
