A3010 4 Mbyte RAM upgrade, the SIMM way

[Zarchos]

Hello everybody.

Pursuing this quest of getting 4 Mbytes for the A3010, if possible with fast chips to overclock the machine, I'd like to be able to adapt a 4 Mbyte 5V 72 pin SIMM module to the A3010 onboard connectors.

Please find enclosed the layout of the A3010 connectors, and the layout of a 5V 72 pin SIMM module. (Apache OpenOffice file).

Diagram.ods

(14.62 KiB) Downloaded 66 times

I need some help to understand which pins must be connected together, to me it's not obvious.

Here is the layout of the A3010 memory connectors :

The layout of the 72 pin SIMM modules is here :
https://en.wikipedia.org/wiki/SIMM#72-pin_SIMMs

[poink]

I believe it's:

Code: Select all

left    right   simm
--------------------------------------
A0-A9           MA0-MA9
VDD     VDD     VDD
VSS     VSS     VSS
RAS     RAS     RAS0 and RAS2 (at least one of the socket RAS lines to [i]both[/i] on the SIMM.
LCAS            CAS0 (for D0-D7 left)
UCAS            CAS1 (for D8-D15 left)
        LCAS    CAS2 (for D0-D7  right)
        UCAS    CAS3 (for D0-D15 right)
D0-D7           MD0-MD7
D8-D15          MD8-MD15
        D0-D7   MD16-MD23
        D0-D15  MD24-MD31
W (/WR)         /WE

You may also obtain any of A0-A9 from the right socket.

You do not have to connect from all of the power pins (VDD and VSS)
on the sockets, but you should connect to all of the power
pins on the SIMM. (Be sure that you get the power pins right!)

There are quite a few things that can change order (bits in
each byte, order of address lines. You can also change the
byte order, so long as the CAS lines move with them.

[munchausen]

Looks right to me poink

I'm reassured to see your A3010 RAM pinout matches with mine.

I still don't know where you're going to actually find space for the SIMMs? Perhaps a daughter-board with a cable?

[Zarchos]

Looks right to me poink

I'm reassured to see your A3010 RAM pinout matches with mine.

I still don't know where you're going to actually find space for the SIMMs? Perhaps a daughter-board with a cable?

I took the pineout from the pineout of the RAM chip used to upgrade to 2 mbytes,

HM514260ZP8 pour 2 Mo A3010.pdf

(973.27 KiB) Downloaded 52 times

with the addition of A9 from what you sent to me (it's the not connected pin 22 of the 514260ZP chip).


I'm looking for the cheapest way : SIMM + wires and a bit of soldering. A cardboard will do the insulation.

[JonC]

Looks right to me poink

I'm reassured to see your A3010 RAM pinout matches with mine.

I still don't know where you're going to actually find space for the SIMMs? Perhaps a daughter-board with a cable?

I'm looking for the cheapest way : SIMM + wires and a bit of soldering. A cardboard will do the insulation.

A simm holder and some strip board will let you easily replace the simm if you need to without desoldering.

[Zarchos]

Looks right to me poink

I'm reassured to see your A3010 RAM pinout matches with mine.

I still don't know where you're going to actually find space for the SIMMs? Perhaps a daughter-board with a cable?

I'm looking for the cheapest way : SIMM + wires and a bit of soldering. A cardboard will do the insulation.

A simm holder and some strip board will let you easily replace the simm if you need to without desoldering.

Yes it's true but soldering will be more tedious (it's easier to do a proper soldering directly onto the module, than on the SIMM holder pins, to me), I think, and the result will use more space.
I'll check anyway ; I've got a huge lot (over 300 units IIRC) of 72 pin SIMM holders somewhere, but I don't know how long it'll take me to find it back ...
Building memory upgrades for the A3000 was my initial goal, duplicating the IFEL board.
I postponed the project after I bought the remaining stock Steve Picton had (all this in case one day I write this game for the Archie demonstrating what it can really do in 2D, and 4 mbytes is necessary to run it : I could provide the game and the memory upgrade at the same time).

[munchausen]

with the addition of A9 from what you sent to me (it's the not connected pin 22 of the 514260ZP chip).

The pinout I sent you has A9 connected, in the same location as in yours!

[Zarchos]

with the addition of A9 from what you sent to me (it's the not connected pin 22 of the 514260ZP chip).

The pinout I sent you has A9 connected, in the same location as in yours!

This location comes from you : I took it from you and simply checked all the others you provided with the layout of the RAM chip ...
So I keep my fingers crossed you made no mistake with A9 when all the others had no errors Anyway there aren't many NC pins available to have one become A9 when the DRAM capacity doubles

[vectorlight]

What brand/size are the chips on your SIMMs?

[Zarchos]

What brand/size are the chips on your SIMMs?

5V 72 pin SIMM module with 2 chips ALLIANCE SEMICONDUCTOR AS4C1M16F5-50JC (5V 1M X 16 CMOS DRAM).
I currently own 16, tested, and 125 are on their way to me (but these units are untested and seller told me I should have a 1 out of 25 defect rate. I'll have to test them 1st with an IFEL SIMM carrier board in an A3000).

[munchausen]

with the addition of A9 from what you sent to me (it's the not connected pin 22 of the 514260ZP chip).

The pinout I sent you has A9 connected, in the same location as in yours!

This location comes from you : I took it from you and simply checked all the others you provided with the layout of the RAM chip ...
So I keep my fingers crossed you made no mistake with A9 when all the others had no errors Anyway there aren't many NC pins available to have one become A9 when the DRAM capacity doubles

Ah ok, I misunderstood your comment then! I found it by looking at the IFEL RAM upgrade PCB scans in the other thread, because I couldn't see it when I looked at the A3010 schematic. However, I just looked at the schematic again and it is present, so I can confirm that it is definitely correct (pin 22).

[Zarchos]

Could you please tell me if this kind of cables has the right characteristics to do the connections ?
http://www.ebay.com/itm/65Pcs-Male-to-M ... Swv0tVAV2q

[munchausen]

Could you please tell me if this kind of cables has the right characteristics to do the connections ?
http://www.ebay.com/itm/65Pcs-Male-to-M ... Swv0tVAV2q

Personally I think I would use a 2.54mm pitch ribbon cable (like IDE cables). You ideally want all the wires to be exactly the same length and not criss cross each other too much, a ribbon cable makes that easier.

[Zarchos]

Could you please tell me if this kind of cables has the right characteristics to do the connections ?
http://www.ebay.com/itm/65Pcs-Male-to-M ... Swv0tVAV2q

Personally I think I would use a 2.54mm pitch ribbon cable (like IDE cables). You ideally want all the wires to be exactly the same length and not criss cross each other too much, a ribbon cable makes that easier.

OK.
It's what I had used for the spider ram failed project.

I don't know if I really need the same lengths, knowing there are 2 series of connectors, and I might very well decide the SIMM could be on the right of the far right of the motherboard.(empty space where there is the metal casing only. Convenient to drill some holes and install a small fan)
This way I could decide to solder not from the top of the motherboard (connectors) but from the other side, underneath.
If all fails (again !) at least the connectors are still usable and the machine could be upgraded the standard way

[Zarchos]

Sunny day here so started working under my cherry tree :

and then realised I had no breakfast and I've still got a lot of putty to put on these walls ... time to work a bit for matters belonging to the 'real, boring' life

[poink]

Personally I think I would use a 2.54mm pitch ribbon cable (like IDE cables). You ideally want all the wires to be exactly the same length and not criss cross each other too much, a ribbon cable makes that easier.

The downside of ribbon cable is crosstalk, of course; because they run next to each other for long distances.

I don't know if I really need the same lengths, knowing there are 2 series of connectors, and I might very well decide the SIMM could be on the right of the far right of the motherboard.(empty space where there is the metal casing only. Convenient to drill some holes and install a small fan)

Length matching becomes more important at higher speeds; but I don't think the Arc's memory bus runs quickly enough (I don't remember serpentine paths on the Arcs). Obviously, keeping the lengths as short and similar far as practical is a good idea though.

This way I could decide to solder not from the top of the motherboard (connectors) but from the other side, underneath.
If all fails (again !) at least the connectors are still usable and the machine could be upgraded the standard way

You might find picking up some 2.54mm/0.1" SIL headers convenient (these things). You can snap them to length.

[Zarchos]

Red screen and blinking led so I did something wrong.
I'll check again tonight (the RAMs shouldn't be dead : I've checked the Vdd several times and the connections are OK).

There's something I need an answer for : as far as the 'Write Enable' signal is concerned, is one connection from any of the 2 series of connectors (left and right) on the A3010 motherboard to the SIMM module enough (pin 47) ?

Also : I've got no connection between the OE (Output Enable) pins on the A3010 motherboard and the SIMM module ... and I don't read any word in the 72 pin SIMM RAM 'dictionary' even closely related to this OE description.

[steve3000]

Red screen and blinking led so I did something wrong.
I'll check again tonight (the RAMs shouldn't be dead : I've checked the Vdd several times and the connections are OK).

What POST message is it giving from the blinking light? This might help track the issue...?

[Zarchos]

Red screen and blinking led so I did something wrong.
I'll check again tonight (the RAMs shouldn't be dead : I've checked the Vdd several times and the connections are OK).

What POST message is it giving from the blinking light? This might help track the issue...?

I'll report tonight, I have to go now.
I've checked again my notes, and I see I've got no connection between the OE (Output Enable) pins on the A3010 motherboard and the SIMM module ... and I don't read any word in the 72 pin SIMM RAM 'dictionary' even closely related to this 'OE'.
I add the question about OE in my previous 'need help' message.

[poink]

I add the question about OE in my previous 'need help' message.

I don't think you need /OE, because the /CAS, /RAS and /WR lines should be sufficient.

AH-HA! I think I see the problem, the write enable line is missing in my original list; connect /WE on the SIMM to /WR on the A3010.

Also, you do need to ensure that the links are correctly set, I believe that's:

• LK22 removed (disable onboard RAM)
• LK21 fitted (enable 4MB upgrades)
• LK20 in position 2-3 (disable onboard RAM)

That's what the IFEL 4MB upgrade uses.

[Zarchos]

I add the question about OE in my previous 'need help' message.

I don't think you need /OE, because the /CAS, /RAS and /WR lines should be sufficient.

AH-HA! I think I see the problem, the write enable line is missing in my original list; connect /WE on the SIMM to /WR on the A3010.

Also, you do need to ensure that the links are correctly set, I believe that's:

• LK22 removed (disable onboard RAM)
• LK21 fitted (enable 4MB upgrades)
• LK20 in position 2-3 (disable onboard RAM)

That's what the IFEL 4MB upgrade uses.

Don't worry I had not forgotten the links had to be changed.
I did connect the WE (pin 47) to one of the 2 W pins on the A3010, and then to both.
Which choice is relevant ? 1 or 2 connections ?

[poink]

Which choice is relevant ? 1 or 2 connections ?

It doesn't matter; the write signal is the same on both sockets.

(There is a separate write signal for the motherboard RAM, which you shouldn't connect to.)

[Zarchos]

Could you read this :
http://www.chiark.greenend.org.uk/~theo ... oA5000.txt

yes it's for the A5000, but it states interesting facts about all SIMM modules :
'that since SIMMs use
parity notation (even non-parity SIMMs), the pin mapping is as follows:

A5000----------------------------SIMM
D0-D7---------------------------D0-D7
D8-D15-------------------------D9-D16
D16-D23------------------------D18-D25
D24-D31------------------------D27-D34
'

again comments and help welcome.

[1024MAK]

It depends what you actually call each signal. Most of the pin-outs I have just looked at class the parity signals as separate to the normal data bus.

Wikipedia
https://www.pjrc.com/mp3/simm/datasheet.html
http://www.interfacebus.com/Memory_Modu ... inOut.html

So where the parity signals are separate, there are only 32 data lines...

Mark

[Zarchos]

It depends what you actually call each signal. Most of the pin-outs I have just looked at class the parity signals as separate to the normal data bus.

Wikipedia
https://www.pjrc.com/mp3/simm/datasheet.html
http://www.interfacebus.com/Memory_Modu ... inOut.html

So where the parity signals are separate, there are only 32 data lines...

Mark

OK understood, not a great find in this text file in reality.

[poink]

OK understood, not a great find in this text file in reality.

The bit that interested me is that it talks about connecting up an inverted DBE to /WR. Unfortunately, I think that's just because the stock A5000 doesn't allow for 4MB expansion boards - which means you've got to get RA9 off the board, which means you can't use the decoded /WR (because that only applies to amounts of memory that are supported on expansion modules).

This seems to be supported by the IFEL SIMM upgrade for the A3000, as that seemingly (at least from photos) manages with the signals off the RAM connector and the signals seem the same (bar the signals to indicate the RAM board presence) in the A3010.

[Zarchos]

I'm quite disappointed this SIMM project doesn't work.
I double checked all the wirings, then started all over again with another SIMM, and still no success.

In case sbdy would like to try and report here, it'd be much appreciated.
I won't come back to it considering the time I've already spent on it.