Quote:
Originally Posted by radfoo
Well done, looks good! Not received mine yet, looking forward to having a play. Shame about the 1Mb chip Ram, what was the problem?
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I just didn't put enough thought into the 1MB chip logic. It should be fixable on the gary adapter only, the original main board is OK.
Quote:
Originally Posted by appiah4
This works on KS1.3 machines with 512K chipram? Like mine? 
Haven't received mine in the mail yet.. But very interested in following up with this (though I assume it would not play ball with my ACA500plus..) |
Sure. It shouldn't interfere with fastram.
Quote:
Originally Posted by TimHarris
Wow, absolutely awesome!
It's my first post here and this forum is great.
Not only did I find exactly what I was looking for in scart cable thread, but also this post was exactly what I was hoping for, thanks a lot!!!
I've had my A500 for many years, but never tinkered with it until recently.. the floppy drive decided it no longer wanted to eat disks.. and oh well, I ordered a gotek + programmer to get that up and running hopefully next week.
Coincidentally I also was offered several A500's in a package deal with some C64's that I was trying to buy and it was an offer I couldn't refuse.. so I popped them open yesterday and noticed no memory expansion.. oh dear.. better browse the web  and now I'm here.
Seeing as I am only after creating a similar setup as my own machine (+512) I will gladly use the sch/brd many thanks!
A few questions though, hope you don't mind;
1. I noticed you blocked one specific field "more than 512K" -> am I assuming correct that all other parts except for this block are to be populated on the board? (so for example do I populate C4, C5, C6 etc)
2. Googling the RTC, I saw elsewhere that when populating a RTC on the expansion, it might require some adjustments to a mainboard to disable to onboard RTC. That applies here too correct?
3. My own machine (and most I remember from back in the day) had a on/off switch (with or without a LED drilled into the top of the case) to switch between 512 and 1, is there a way of adding that to this design?
(i have to be honest here, I don't ever recall turning mine off, so I don't even know if that is necessary)
Many thanks,
Tim |
No worries.
1. Yes, you don't need the 74F139 and don't need U2, U3. Also C4-C6 is for the extra memory chips, so you don't need them either. I think the total parts list for 512K is:
CTX: 2x28 2.54mm right-angle female header (or buy 2x40 and cut it).
U1: SOJ42 1x16M DRAM
C1,C2,C3: 100nF X7R 0805 capacitors (maybe one is enough)
2. Only needed for A500+ (the "plus")
3. There's an enable jumper on the board, which could be wires and a switch if wanted. But don't drill holes in your case
I've still got 1 spare PCB if you want to pay the postage.
Cheers,