The humongous Sandy Electronics thread...

[Dave]

Even *with* VAT the parts are a good price, and at least I would be able to get them. However, the company has got back to me and restated that they will ONLY accept a bank transfer from the US. Very few banks here offer IBT any more.

If anyone within the EU would be willing to place an order on my behalf, then reship to me, I would happily cover all their costs. If that person also is VAT registered, it would reduce the price by about 20% (about 65 euros)...

OR: if anyone can suggest an alternate supplier for DIN41612 type B 2 row 64 pin right angle female connectors for around 2.5€ each? I need 100.

[Dave]

The connector order problem is now hopefully resolved. Thanks go out to Rich at RWAP.

I'm having a couple of problems with the Minerva MK IIs. I understand one of the problems quite well, but the other is a little more complicated. I've updated the customers, and hope to have this resolved soon.

I have built a few Minerva MK 1s that work with no problems.

[Dave]

I've been working on SuperRAM a little more recently. I have almost finished the power supply area. I've managed to squeeze a track between the pins of the SOP32 without breaking design rules. I've started on the ground fill, including using the ground layer as a heatsink for the 7805.

I have checked parts placement for physical clashes and done a little thermal modeling and it's good.

SuperRAMp2.jpg (22.44 KiB) Viewed 4120 times

As you can see here, the power supply is at the top, the SRAMs are central - mostly because there's a good amount of track fanout and placing them higher or lower forces a wider expansion card. The GAL containing the custom logic, the DIP switch for configuration and various R's and D's around the GAL. I used through-hole because it gives me extra routes to enable the through connection while protecting signal quality.

The SuperRAM implements 896K of full speed SRAM which is highly configurable. What's more, you can optionally shadow the internal 128K so reads come from faster SRAM. This includes video RAM and can give some quite reasonable performance improvements. TK2 runs from SRAM at the same speed as from ROM, so networking works correctly with soft-loaded TK2. If you have Minerva, there are a couple of ROM areas where images can be loaded that are persistent across reboots, as long as power isn't taken away. I'm sure a few of you can think of fun things to do with that.

The SuperRAM manipulates lines SP0-3 to relocate expansion cards into the highest available locations in the memory map and maximise available RAM.

SuperRAMp3.jpg (22.71 KiB) Viewed 4120 times

A different angle, so hopefully you can see the chip markings.

Note, all layers are printed in black. My printer prints at about 101% so the pin spacing is very slightly off. I have not connected ground to VIN - it just looks that way. Note I have used ground to create a heat pipe to draw heat away from the 7805. There's an electrolytic and ceramic cap on each side of the 7805, for maximum smoothing. Some tracks exist for spacing purposes and will be deleted in the final design.

Don't worry, the GAL will be socketed.

When this design has been released and reached break-even, I will release the gerbers, schematics and GAL code under a non-commercial free use license. That way, people can experiment, make their own modified versions, etc, but they can't sell them. Once I have finished selling them, I will lift the non-commercial restriction and they will be fully open licensed to do with as you wish.

[tofro]

Dave,

is there any reason why you use the good old electrical heater 7805 instead of something "better"?

Tobias

[Ralf R.]

I will take one

[Dave]

Dave,

is there any reason why you use the good old electrical heater 7805 instead of something "better"?

Tobias

It's a business decision. I have the caps and regulators, so they're a sunk cost. The regulators I bought in bulk, so they only cost me 3.9c each, anyway. I couldn't put a better regulator on the board unless I spent 20x that.

I need to control costs with this board so it can hit a target price, and still leave enough margin for it to find resellers, like RWAP. It is a fundraising project for later projects, as always.

This is a small and easy board aimed at people with sub-Gold Card systems that aren't hugely expanded anyway. It's more or less custom-designed for QL-SD buyers, so they can have a QL with SD storage and a lot of RAM.

Larger boards will have a more advanced supply on them.

[Derek_Stewart]

Hi Dave,

The board looks good, can you put me down for a board when you start producing them.

Derek

[Dave]

Thanks Derek

To avoid confusion, because I know it looks a little weird, but there are some tracks laid on that board just to calculate fanout so I know where to place other components. Those tracks will later get ripped up. The idea is to still leave plenty of free space so all the through connections can be made afterwards.

[Dave]

After a lot of head scratching trying to get the GAL logic on there and route all the thru connections, and failing, I have changed from using a DIP GAL to using PLCC surface mount GAL and supporting components. This leaves the back of the board completely open, and makes routing a *lot* easier.

It may even allow me to shave off another 5 mm from the PCB, saving me *calculates* $0.05 per board!

[Dave]

Oooh, these look pretty See what you have wrought, Tim?

1GB Compact Flash cartridges for the UltimIDE.