WANTED - 1MB 100/120ns simms 30 pin

[exxos]

I'm looking for 3 chip or 9 chip (parity preferable) 100ns (or 120ns) 1MB simms 30 pin, matched set of 4.

If anyone can donate some or can sell me some at a not a silly price then let me know. I am in the UK.

I am doing a bit of research into some odd STE RAM problems. I am not sure if speed is a factor. All the simms I have are generally 70ns,80ns.

[mrbombermillzy]

I know I have a 40 3.5" floppy case full of 30/72 pin SIMMs that I actually brought with me to CL1.

I remember having quite a few 30 pin SIMMs in there, but not sure if theres any of the slower type, and even less chance of matching 4.

Nevertheless, I will have a good go at locating that small case and get back to you with the results.

If we do strike lucky, you are welcome to them. :)

[exxos]

If we do strike lucky, you are welcome to them. :)

:thanksyellow:

[mrbombermillzy]

If we do strike lucky, you are welcome to them. :)

:thanksyellow:

No problem.

BTW I also forgot to lessen the chances further due to needing parity SIMMS :lol:

[exxos]

BTW I also forgot to lessen the chances further due to needing parity SIMMS :lol:

I can still test without parity. Just those always seem to aggravate the problems more. So preferable to have them.

[exxos]

So parity is preferable but its more the speed of the RAM which is going to be the main issue it seems. Same brand of simms per stick is preferable but likely not that critical either.

So I basically need.

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

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

I already have a stash of 80ns and 70ns ones. I assume 150ns or slower don't exist or may not work anyway in the STE. :shrug: I don't remember seeing Atari recommending a min/max simm speed anywhere :shrug: I know the STFM had 120 and 150ns DRAM. I half recall seeing 250ns at some point?.. not really sure though. Looking at the STM images in the motherboards section, I don't see slower than 150ns on those..

[mrbombermillzy]

BTW, Im going to have a good look for the SIMM box tomorrow (when I can bang about without consequence!), so Im still on the case with this.

However...80ns is 12.5 Mhz, so something thats 100-150ns is in the ~6-10Mhz range...250ns is 4Mhz. These are very early SIMMS and I would have thought most of the slower SIMMs got chucked (in the same way as the more modern higher capacity RAM chips are held on to in preference over lower ones; i.e. people want their mainboards maxed out *not* 'min'ed out! :lol: ).

[exxos]

BTW, Im going to have a good look for the SIMM box tomorrow (when I can bang about without consequence!), so Im still on the case with this.

:thumbup:

However...80ns is 12.5 Mhz, so something thats 100-150ns is in the ~6-10Mhz range...250ns is 4Mhz. These are very early SIMMS and I would have thought most of the slower SIMMs got chucked (in the same way as the more modern higher capacity RAM chips are held on to in preference over lower ones;

Not sure how it works out. Though 150ns works on a lot of machines.

i.e. people want their mainboards maxed out *not* 'min'ed out! :lol: ).

It's the exxos way ;) :P

[mrbombermillzy]

Not sure how it works out. Though 150ns works on a lot of machines.

Yeah, theres probably some sort of tolerance or other variable Ive forgotten about over the years. I'll just send you the SIMMs and you can see what does and doesnt work. :lol:

[ijor]

I already have a stash of 80ns and 70ns ones. I assume 150ns or slower don't exist or may not work anyway in the STE. :shrug: I don't remember seeing Atari recommending a min/max simm speed anywhere :shrug: I know the STFM had 120 and 150ns DRAM. I half recall seeing 250ns at some point?.. not really sure though. Looking at the STM images in the motherboards section, I don't see slower than 150ns on those..

However...80ns is 12.5 Mhz, so something thats 100-150ns is in the ~6-10Mhz range...250ns is 4Mhz.

The DRAM speed grade is the access time, not the cycle time. Access time is the delay between setting up the address and data out being ready. Cycle time is the minimum time between two consecutive accesses (the inverse of the max frequency).

The ST accesses RAM at slightly over 4MHz (two CPU cycles per RAM access). Ideally it should use 120ns RAM that have a 220ns cycle time, or better. In theory 150ns RAM might be too slow, cycle time according to specs is 260ns (3.84 MHz). But these specifications are for the worst voltage and temperature case (70C). I know Atari shipped boards with -150ns RAM. May be Atari tested the chips, or may be the manufacturer guaranteed it should be ok at "normal" room temperature.

I'm not so familiar with the STE timing exact details, but the requirements should be about the same as the ST/STFM, if not identical.

Using slightly faster chips is usually ok. Actually you might be using faster chips without knowing. The manufacturer guarantees a given chip is not slower than the specs. It doesn't guarantee it is not faster.

But if it is much faster it might not work. i.e., the output hold time for faster chips is shorter, which could be a problem. Also, especially if the technology changed, faster chips are more sensitive to noise.