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Nikodem
9th March 2012, 12:38
Recently I bought a SCSI controller - Protar A500HD, after trying to run it as a memory expansion I've failed, because I do not have proper RAM stick.

The controller needs Protar RAMs, they are in standard 72pin SIMM format, but it look like they are somewhat different (it is stated in the manual, as far as I understand german, and also some people told me that).

I would be very very glad if someone had these sticks for sale, or at least could give me any info how different they are - maybe one can convert normal SIMMs into Protar ones.

rkauer
9th March 2012, 19:52
I think they are not different at all. Use good 60ns sticks and that's it.

At least both BBoAH (http://bboah.amiga-resistance.info/cgi-bin/showhardware_en.cgi?HARDID=1234) and AHDB (http://amiga.resource.cx/exp/search.pl?product=A500HD&company=Protar) says the same: the unit uses 72-pin SIMM, which is uncommon for A500 expansions. Not the SIMM itself is different, it is just different from other devices of that era.

Expansions for A500 normally uses DIP, ZIP, 30pin SIMM and (God forbid!) SIPP packages.

Nikodem
15th March 2012, 23:45
They are different. It is stated so in the manual and several people confirmed that issue. Also an article from a polish amiga magazine confirms that the SIMMs have to be of special kind.

Whatsmore, I've tested over 20 different SIMM sticks - be it single and double sided with different timings and different size of course. Nothing worked, and some of them stopped the SCSI controller from working also.

Zetr0
16th March 2012, 00:04
@Nikodem

I suspect that this is a refresh size issue... not refresh speed.

I cannot tell directly what is required but I would harzard an educated guess that this device only works on Memory SIMMS with 1K refresh - I will see if I have any in the towering spire of RAM that I have.

Zetr0
16th March 2012, 11:17
Another thought that did just pop into my mind is that the 72pin SIMM socket might be faulty - damaged / corroded pin or perhaps a dry solder fault on the PCB

I could be worth an inspection with a magnifier, a clean and perhaps a reflow of solder of the pins.

Nikodem
16th March 2012, 11:29
Zetr0, I've inspected the SIMM socket thoroughly. There are no faulty/corroded/cold solders or faulty pins. Overal condistion of the device is good, and it is very unprobable that this is such kind of issue. Especially that connecting a normal SIMM makes the whole device unoperable, so for sure there is some communication with the stick.

As I said I'm near to sure that this device needs proprietary SIMMs. Could you explain to me the refresh size issue? What's that? I've never heard of that :(.

Maybe some other A500HD users can help? Maybe someone has some sticks for that and could post some info and/or photos?

Zetr0
16th March 2012, 14:07
@Nikodem

thats very interesting... well other than HP/Compaq, I am unaware of any proprietary based 72 Pin SIMM's.... thats not to say that there are none out there, its just I haven't seen them.

Now, lets talk refresh sizes..... but before we do that we need to talk a little about the matrix


No no.... not the film.... its the memory modules layout...... now imagine if you will the stick of ram you have in your hand (yes pick one up and look at it) is essentially a spread sheet.... like Excel.... it has an X number of CELLS and a Y number of CELLS.... each CELL will have a number of bits....

so.... now you have that in your mind you can envision three distinc matrix shapes -

Wide (horizontal rectangle... with more X Cells than Y Cells)
Narrow (vertical rectangle... with more Y Cells than X Cells)
Square ( an identical number of X and Y Cells )

now, at this point I need to point out that some controllers will only take a certain matrix.... either Square, Narrow or Wide..... some controllers are clever and work out what you have - but I doubt that on most Amiga Hardware lol


Refresh Sizes

now imagine a 2Mx8 DRAM chip, lets say this has 2000 rows (Y) , 1000 columns (X), and 8 bits per column -- a total capacity of - yes you guesed it 2MB or 16Mbit.

As you know DRAM "dynamic" RAM memory must be refreshed, hundreds of times each second in order to retain data. DRAM memory is designed around tiny capacitors that store electrical charges. These charges gradually lose their stored charges if they are not refreshed or energized.

I should also mention for completeness that the process of reading data from the memory array drains these charges, because of this the memory cells areprecharged before reading.

So simply put; A refresh is infact the process of recharging the cells in a memory chip and these cells are refreshed one row at a time with a usual one row per refresh cycle.


Refresh Rate

Refresh rate refers to the total number of rows that it takes to refresh the entire DRAM array for example - 2000 (2K) or 4000 (4K) rows.

Refresh Cycle

Refresh cycle refers to the time it takes to refresh a row or, anyoingly confused with the time it takes to refresh the entire DRAM array.

Sadly because of this while RAM Refresh can be accomplished in many different ways it is also one of the reasons it can be a confusing.


A little more on Refresh Rate

Now, a Refresh rate is determined by the total number of rows that have to be refreshed on a memory chip. because of this memory chips are designed for a particular type of refresh - i.e chips using 4K refresh will have about 4000 rows, which means that it will take about 4000 cycles to refresh the entire array.

This obviously differes with chips using a 2K refresh as they will have about 2000 rows, and chips with 1K refresh will have about 1000 rows.

but this is not dependent of the SIMM memory size - DRAM capacity is rows x columns x width.

So we can say that a 4Mx4 chip is 4 Megabits deep and 4 bits wide for a total of 16Mb (or 2MB). Lets assume for the moment that this chip used a 4K refresh, it will be organized into 4000 rows x 1000 columns x 4 bits per column this is a total capacitty of 16Mb (2MB).

However If this chip uses 2K refresh, it will be internally organized into 2000 rows x 2000 columns x 4 bits per column with a total of 16Mb (2MB) again, the capacity is the same, yet the organization and refresh are quite different.


There are a few DRAM fresh schemes the most common are 1K, 2K and 4K... now some Amiga memory controllers wont support 4K refresh, I am sure that Apollo's struggle with 4K refresh modes and prefer a 2K (Square Matrix) refresh


I hope that ramble helps.

MC680X0
16th March 2012, 15:49
@ Nikodem

I've found an original Protar 2MB memory SIMM (see pics), that belonged to the Protar SCSI device that I had bought some years ago. Because it was only 2MB, I've replaced it with an 8MB module. I've sold the ProtarHD some time ago, so I don't know exactly what type of memory the 8MB module was anymore.

Zetr0
16th March 2012, 17:33
Now isn't that something!

I would be curious as to the pinout..... before one tested it you should check the ground and power plane pinouts on the edge connector (so one didn't fry it when plugging it it...

you could do this with a multi meter and this chart from pinouts RU (http://pinouts.ru/Memory/Simm72_pinout.shtml)


Actually this could also be done on the Protar socket as well to ensure that ground and power line up where they should...

Nikodem
17th March 2012, 10:19
I would like to buy this one, MC680X0. PM sent

Zetr0, I guess that the pinout is similar. At least what I can see in the picture is that the presence detect signals are in the same place.

Nikodem
18th March 2012, 12:50
I'm still looking for theese SIMMs for Protar, the bigger the better (the best would be to find 4MB or 8MB ones).

Nikodem
29th March 2012, 22:18
@ Nikodem

I've found an original Protar 2MB memory SIMM (see pics), that belonged to the Protar SCSI device that I had bought some years ago. Because it was only 2MB, I've replaced it with an 8MB module. I've sold the ProtarHD some time ago, so I don't know exactly what type of memory the 8MB module was anymore.

PM about shipping and payment sent.

Still looking for other sticks for this device, possibly bigger than 8MB.

MC680X0
31st March 2012, 08:13
PM answered.

piacc64
31st March 2012, 10:28
1/2mega in photo are half mega not 2 mega, i understand, please confirm if in photo are another simm

Nikodem
31st March 2012, 11:28
Payment sent. Waiting for it's arrival ;).

---------- Post added at 10:28 ---------- Previous post was at 09:43 ----------

Can a mod set this topic to wanted still? I found one RAM stick, but I'm searching for more, perhaps bigger than this one.

Of course I cal always make another topic in the wanted section.

MC680X0
1st April 2012, 11:11
1/2mega in photo are half mega not 2 mega, i understand, please confirm if in photo are another simm

It's 2MB. I've tested it some time ago with a ProtarHD device.
These memory sticks where pre-printed with 1/2MB, because
some memory banks actually had 1MB and others had 2MB on them.

MC680X0
4th April 2012, 15:52
@ Nikodem

Money received, many thanks! :) The Protar Ram module
is on it's way to you.

davideo
4th April 2012, 16:49
Can a mod set this topic to wanted still?

Do you still want this set as 'Wanted'?

Dave G :cool:

Nikodem
4th April 2012, 17:07
Can a mod set this topic to wanted still?

Do you still want this set as 'Wanted'?

Dave G :cool:

Yes, as this is a 1MB or 2MB o 512kB module ;). And I still hope for finding anything bigger - 4MB or even 8MB, that would be perfect.

Nikodem
19th April 2012, 16:45
RAM Received, I will post feedback as soon as I have a second to test it in my Protar :).