exxos's Atari, Amiga & retro forum

@ijor Do you know how the RAM is organised. I mean I'd assume when 2 simms are in place, the RAM is literal from 0-2MB. But when there are 4 simms, is it still literal from 0-4MB ? or does the RAM get interleaved, so it would use 1 word from bank 0, then 1 world from bank 1, then 1 word from bank 0.. etc ?

exxos wrote: 13 Mar 2024 19:05 So I basically need.

4x 1MB simms 100ns,120ns,150ns.

I have to have the full 4MB set of all the same speed ratings.

These are all SIMMs I have with those speeds if you can't find better matches.

Troed just pipped me to the post.

Ive just found my box of RAM and unpacked the 30 pin stuff.

Unfortunately, they are all 70 or 80ns rated apart from four sticks which I believe to be 256Kb SIMMS that are 150ns.

They are identical to the top set in Troeds picture (with the Siemens chips), other than being rated at 150ns instead.

Heres the datasheet if you havent already got it:

Let me know if you want me to send.

troed wrote: 14 Mar 2024 10:13 These are all SIMMs I have with those speeds if you can't find better matches.

Cool!. Think first set is a 256K simm... but I didn't actually try 256K simms..

EDIT:

mrbombermillzy wrote: 14 Mar 2024 10:41 Unfortunately, they are all 70 or 80ns rated apart from four sticks which I believe to be 256Kb SIMMS that are 150ns.

ah thanks for looking anyway :)

I am going to try 256K in a moment.. I am not sure if its the amount of RAM used or the fact its 2 or 4 simms being used.

Oddly 120ns 256K simms failed to detect the full amount. But 150ns found the full 1024K and seemed OK. So it must need the full 4MB to show the problem.

So @troed , if I can borrow/buy/swap your 1MB sets then I can give them a try.

exxos wrote: 14 Mar 2024 11:43 So @troed , if I can borrow/buy/swap your 1MB sets then I can give them a try.

Just tell me what you want and I'll send them - but I don't have full sets of the 1MB ones :(

troed wrote: 14 Mar 2024 12:07 Just tell me what you want and I'll send them - but I don't have full sets of the 1MB ones :(

ah, I've not woke up yet, didn't notice there wasn't full sets. Let's hold for now and see if I can find some other odds ones to make up the set first...

troed wrote: 14 Mar 2024 12:07 Just tell me what you want and I'll send them - but I don't have full sets of the 1MB ones :(

Looking again there are 5x 120ns 1mb Simms. So that should be enough to test what I want I think..

I've been looking around the internet and there is basically nothing about unless I want to pay $50 a stick from the USA :roll:

exxos wrote: 14 Mar 2024 10:11 @ijor Do you know how the RAM is organised. I mean I'd assume when 2 simms are in place, the RAM is literal from 0-2MB. But when there are 4 simms, is it still literal from 0-4MB ? or does the RAM get interleaved, so it would use 1 word from bank 0, then 1 world from bank 1, then 1 word from bank 0.. etc ?

It is not interleaved. Any access at the lower 2MB goes to the first bank, any access to the higher 2MB goes to the second bank.

Turns out I had a few more SIMMs, although 150ns they're too small. And then I have the biggest, baddest, most MASSIVE SIMM ever too ;)