Memory Upgrade without problems

Som alle Archimedes ejere har iagttaget, er 1 Mbyte ikke nok 'husker'. At forsøge at bruge f.eks. Acorn DTP, er et mareridt.
Derfor er der nogle ret smarte medlemmer af BIG BEN CLUB i Holland som har fundet udaf hvordan man upgraderer sin A310/305 til A340 (Dvs. 4Mbyte)

Denne artikel er oversat fra hollandsk til engelsk af Fred (SysOp på Acorn BBS i Holland) og herefter af mig til dansk.
Derfor gives der ingen garanti for at oplysningerne i artiklen er 100% rigtige.

Hukommelseskredsene der er i en A310 har typenummeret NECD41464 C-12, disse skal udskiftes til eksempelvis Fujitsu MB 81C1000-10.
(Nu : 4x 64 Kbit DRAM x 32 = 1024 Kbyte. Efter : 1x 1MBit x 32 = 4096 
Kbyte) 
se figur 1 og 2.

Man skal være meget forsigtig, specielt med statisk elektricitet da nogle af kredsene i Arc'en er ekstremt følsomme overfor dette.
Undgå ærgrelserne og iagttag følgende regler :

1. Brug et jordet metalbord eller lignende.
2. Sørg for at loddekolben er jordet, brug eksempelvis radiatoren som jord.
3. Lad være med at have din nyeste nylon-polyester Dario Alfonso skjorte på, heller ikke den store uldne pædagog-hønsestrik sweater er brugbar.
4. Rør med jævne intervaller metalbordet eller andre jordede genstande.
5. Brug en moderne loddekolbe, ikke en 200 Watts tagrende-loddekolbe. Brug f.eks. en Weller Vp 700 EC.

Forberedelser etc.
Fjern låget på Arc'en, fjern evt.backplane, poduler og andet ekstra udstyr (Gem skruer så du kan finde dem igen!). Floppy-drev og hårde-diske skal også ud.

Remove the lid of the Computer.
Be careful!!
At the back/underside of the Archimedes you will find two very sharp-edged 
screws which can do severe damage to the motherboard if you slide this out. 
You have to remove these first!
After this is done you can remove the back-panel of the machine and remove 
the connecting leads (after first writing down which lead was connected to 
which point).
Now you can slide out the mother-board.

RAM-Removal
===========

You will have to remove all 32 RAM-chips by cutting all pins with a 
(small-jawed) pair of tweezers and also IC 59 (LS 138). You have to cut 
them as near to the chip as possible.
After this you can remove the remaining pins (18 per IC) by means of the 
soldering-bolt and using a pointed pair of tweezers. Work fast, but careful.
You will have to remove all remaining solder with a 'tin-sucker', if that is the correct word. All the tiny holes should be empty. You should also suck 
out the holes of RA2 and -RAS near IC 59 (RA2 to the left of pin 3 and -RAS 
to the right of pin 13)
Carefully clean the whole area with for example Chlorothene.

Preperations of the mother-board.
=================================

Now you'll have to cut and remove a few connections on the motherboard with
a very sharp (surgical) knife.
Of all RAMs (top- and bottom-side) pins 1, 4 and 17.
Pins 2, 3 and 15 have to be un-connected to the resistor.
All pins except 1,3,8 and 17 of IC 59 (LS 138).
If you are clever enough you can maintain the connection of pin 17 with the
Data-resistor on 8 RAMs (IC 52, 54, 56, 58, 61, 63, 65, and 67)
Now you will have to make some connections:

- Connect all pins 2 of the RAMs to each other and to IC 59 pin 2

- Connect all pins 3 of the RAMs to each other and to MEMC pin 38 (-RAS)
   (figure 6) near IC 59

- Connect all pins 5 of the RAMs to MEMC pin 30 (RA2) (figure 6) near IC 59

- Connect all pins 15 of the RAMs to each other and to MEMC pin 37 (RA9) 
  (again figure 6) 

- Connect pins 7 and 8 of IC 59 to one another

You can make a lot of connections by using U-shaped, isolated wires 
(Wire-Wrap wire) (see figures 3 and 4), this is a very clean way of working.
Of all RAMS you have to connect pins 1 and 17 together and from there to the DATA line-resistor(figures 3 and 4).


(I hope this is clear to you, if you have any more questions, ask!! Fred)


All connections have to be made by sticking the U-shaped wires from top to 
bottom into the motherboard.
Now you can stick in the RAM sockets together with the connecting U's and 
solder the lot.

Checking  etc
=============

Check all connections, also check on unwanted connections.
If everything is allright you can insert the RAM-chips, place the 
mother-board back into the case and re-connect all leads.

(violet=-5V , Red=+5V , Yellow=+12V , Black=0V)


A note
======
The original article is 5 pages long, I have shortened it as you will 
understand.
Here in Holland the whole affaire is quite easy and straightforward, because
there are a few members of the Big Ben Club (users of Acorn Computers) that  
have acquired a lot of experience in upgrading machines to 4 Megabytes the
last few weeks. All in all there are some 50 or 60 A340's now I think.
Anyone coming into troubles while working on the upgrade has the possibility
of asking one of these experienced users, he can even take his machine and
someone will do the upgrade for a small amount of money.
For you it isn,t that easy, but with some experience in soldering in
computers you can do it.
If you are totally new in these matters it is NOT advisable, you will
understand this I hope.

I hope you can do something with this information, in the worst case 
ofcourse you can send or bring your machine to Holland, the total price
for the upgrade is around 1000 guilders and I am sure that this will 
(in total) be cheaper than ordering a Watford memory upgrade, which isn't 
even ARM-3 compatible.
 
greetings and I suppose I'll be 'hearing' from you.
           
                                        Fred