exxos's Atari, Amiga & retro forum

rubber_jonnie wrote: 15 Jan 2024 09:03 Depends when my parts arrive. I think I will have enough for initial configuration of the video circuit and a full power on test this week, but I won't have all the RAM for a couple of weeks I think, though hopefully enough for a basic test.

Even a basic test would be nice.

One thing I hate is waiting for parts (not one or two days, but 2 or 3 weeks), as it puts your project on hold...

HigashiJun wrote: 15 Jan 2024 09:44 One thing I hate is waiting for parts (not one or two days, but 2 or 3 weeks), as it puts your project on hold...

Oh, I know. Worse is when you don't know how long the delay is going to be.

My latest wasn't actually the chip but the data, three weeks after I had the hardware ready I got the ROM image.

@stephen_usher @HigashiJun

Yeah, it's a real bind.

My EPROMS are at least in the country and should hopefully be delivered tomorrow, but the RAM seems to be transported by Donkey and has a predicted arrival of 25th. The perils of AliExpress.

I've sourced enough RAM from the UK to be able to test, but it's just way too expensive to populate the board fully, hence my order from China.

If I also build the 610 expansion board, I'll need to source a truck load more RAM of the same type as it adds another 24K to take it out to 32K total. I won't start on that until the 600 is running though.

The rest of the ICs are coming from the UK so should be here this week, but the BoM is just not good and missing quite a few ICs, and whilst you can find them buried in the docs, they don't always give accurate descriptions of what they are.

I may do an updated BoM with what I've found so people following can have an easier time of it. At least when you bought a kit back in the day it hopefully had everything you needed included.

@rubber_jonnie

That's the draw back of every new project...

You are convinced you have the required parts, but as expected you don't have all of them and have to order and wait until they reach you.

And yes, crappy BOMs don't help much.

:evil:

stephen_usher wrote: 15 Jan 2024 09:48 My latest wasn't actually the chip but the data, three weeks after I had the hardware ready I got the ROM image.

:o

Woo Hoo

The Last of the Resistors just arrived :)

Is it just me or does this sound like an old western movie...

:lol:

What RAM chips is it using?!

Might be faster and cheaper to design a PCB to sit in the sockets which allows more common (and cheaper) ones to be used. :-)

stephen_usher wrote: 15 Jan 2024 12:22 What RAM chips is it using?!

It's using 2114 static RAM, 18 in total. 2 for video RAM, the other 16 for normal RAM. So 1K of video RAM and 8K of system RAM.

stephen_usher wrote: 15 Jan 2024 12:22 Might be faster and cheaper to design a PCB to sit in the sockets which allows more common (and cheaper) ones to be used. :-)

It was a disappointment to find it was static RAM, as I have loads of dynamic RAM ICs, but the problem is simply that I don't have the skills to design something like that. I'm sure somebody could easily create a board hosting an 8k static RAM IC, but whilst I am good at repairs, I wouldn't know where to start with something like that.

Oh, static RAM is easy, it's just like an EPROM which you can write to in terms of wiring things up. No fiddling with RAS and CAS lines or multiplexing in general. It's very simple. Wire up the address lines, wire up the data lines, wire up the chip select and the R/W line and usually Bob's your aunty.

That would be why they're using static RAM, no need for a refresh of multiplexing circuitry.