Would you pay $100 for 8MB RAM?

[Ral-Clan]

Hi,

Been trying to track down some RAM chips for my A500 sidecar. I've already got 2MB RAM in there which I got for free by ripping RAM out of old PC motherboards.

But it is expandable up to 8MB - only thing is you have to use 1M x 4 chips, which seem to be a little hard to get.

Only source I can find online will cost me about 68 Euro, which is nearly $100 US when you factor in shipping.

Since that's more than I paid for my A500 and sidecar, I'm rather inclined to forsake this upgrade.

I don't think it's an unfair price, just a little hard to justify.  I can get by with 2MB fast (I've already got another 2MB chip in there), but some things run a little tight on RAM.

Crazy the way old RAM dips in value then skyrockets as it becomes rarer!

I did find this online --- seems much cheaper, but I'm not sure if it's the same type of chip:
http://www.alibaba.com/product-gs/705697837/_Memory_IC_5962_9084702MRA.html

[Ral-Clan]

Holy crap!

I just figured out that a lot of the old 1MB 30-pin SIMMs I had been saving from old PC motherboard have 1M x 4 DRAMs on them.....BUT they are all SMD (surface mounted) chips.

I would have to make adapters to use them as DIPs:

http://farasbee.com/blog/2012/03/19/quick-hacks-a-diy-smd-to-dip-adapter-in-five-minutes/

Would be a slight challenge, but could be fun!

[Ral-Clan]

Why not write Kipper2k a note and ask him about his $50 (or thereabouts) 8mb 68K board that auto configures, and ditch that ugly power hungry sidecar thing?  :knuddel:

Yeah, I was looking at that --- but my A500 is already crowded inside by several expansions!

[Ral-Clan]

http://www.amiga.org/forums/showthread.php?t=64203

Yeah, those are the wrong kind.  I need 1M x 4.

Anyway, I found out I have about 16 to 20 MB worth of SMD style 1M x 4 chips on SIMMs.  I just need to desolder them and make adapters.  I'll try that first.  If not, maybe I'll buy the expensive DIPs.

[Ral-Clan]

Mechy's got them for sale on his website, but they might still be too expensive, $88 for 16 of them.

http://a4000t.com/store/index.php?main_page=product_info&cPath=66_108&products_id=226

I got hold of some 1Mx4 SOJ chips off some PC SIMMS and modded them using 20 pin DIP IC sockets for my VXL*30 A500 accelerator. Not very pretty but now I have 8MB 32bit fastram and it works 100%

I'll post some pics when I get home tonight.

That would be great. I have some SOJ RAM chips on some old video cards, but they all appear to be the wrong kind --- I thought they were "A3000 type" zips, but too many pins.

I'm going to buy some perf board today to make the adapters for the SMD chips.

[Ral-Clan]

Orcish 75,

THANK YOU FOR POSTING THOSE PICS

It's not only good to see that another Amiga user has already attempted to do what I am about to do, but your idea to use IC (DIP) sockets is genius! It will save me from buying perf board and pin headers!  I have a TON of old IC sockets on various scrap gear!

I can desolder the IC sockets with a desoldering pump.  I plan to use a hot air gun to desolder the SOJ RAM chips from the SIMMs. How did you desolder the RAM chips?

It looks like you bent the little curved-under legs outward to extend them to the DIP socket holes, is that right?

THANK YOU!

PS: My chips are SOJ like yours. I had been referring to them as SMD (Surface Mounted Device?) because because they were soldered straight to the SIMM board without through hole, but I guess my terminology was wrong.  I thought ZIPs were SOJ because of the little bend in the legs - but I am all "straightened" out now!

[Ral-Clan]

There is also a commercial adapter for SOJ DRAM (for 1Meg & 4 Meg DRAMs) to 20Pin DIP  
AK20D300-SOJ
http://www.accutekmicro.com/pdf/ProductPDF-470.pdf

Thanks,

Yes, I had seen the commercial adapters. But for the cost of them (about $3) I might as well have gone with the original 20PIN DIP RAM chips I saw for sale at $3-4 each.

[Ral-Clan]

Thanks!  I will have to look at your pictures to see what you mean by "inner" and "outer" legs (I think I know what you mean).

I will post pictures with the results (hopefully good results)!

Great tip, about using a spare IC socket as a holder while soldering, by the way.

[Ral-Clan]

Okay, I got 2MB of the chips working now.

My soldering / adapter construction job looks hideous (those little legs are TINY), but they work and have passed five RAM test passes so far.

Initially I thought it wasn't going to work, as I got a yellow screen.  But testing showed there were lots of cold solder breaks (from the way I was pushing in the adapters - now corrected).

Unfortunately, I did not have the nice DIP sockets that Orcish used for his adapters.  Mine are the more common, cheaper kind and you cannot stick a blob of solder on the pin openings to solder the chip legs directly to.  So, I've had to stick short pieces of wire in each pin socket, then solder the chip legs to those.  Because of this, the chips are suspended above the DIP socket on stilts.  I'd be embarrassed to show anyone this, but here is a picture (click to enlarge).



Sorry about all the messy solder, but even with a fine tip soldering iron, the legs are so small it's like doing surgery with a meat cleaver.

Two MB done - and it took me about FOUR hours!  I'm getting better at it though.  Only six more MB to do.  So far one RAM chip ruined (broken leg) and one socket ruined (through my initial practicing).  I have extras, fortunately.

[Ral-Clan]

Up to 4MB RAM now (another four chips done and passed a RAM test).  This batch didn't pass the initial RAM test (no yellow screen though) and again it was a solder joint problem.

Going for the long stretch - I have to do a batch of 8 chips (another 4MB) to bring it up to the 8MB maximum.

My soldering job is getting much neater and I'm getting slightly quicker, but it should still take about 5-8 hours!

[Ral-Clan]

Setback: my desoldering iron burnt itself out.  I guess I left it on too long???  I didn't know you could leave something like this on too long - it was on all afternoon while I was working as I was constantly switching back and forth between the soldering iron and the desoldering iron.

So things are on hold 'til I can source a new one (I prefer the kind that heats up on its own).

[Ral-Clan]

I've ordered a new de-soldering iron (solder sucking iron) off of ebay, but it will take a few weeks for it to arrive.

However, I am able to continue working as I've found I can heat up the old de-soldering iron with a butane torch and use it that way for now.

I also ran out of sockets for 20-pin DIP IC's.  So I've had to switch to using 24-pin sockets.  This is not a problem because I will just leave part of the socket extending out beyond the RAM sockets on the Supra 500XP board.

The one good thing about these 24-pin sockets is that they are the higher quality, thick pin type that Orcish used on his RAM hack.  I must admit, this type of socket makes the job MUCH easier.  I can put a solder blob right into the little pin holes on the DIP socket and not have to use little wire "stilts" like I was before (except I still need four wire jumpers for the corner "outside" legs of the SOJ chips where they don't reach).  I wish I had had enough of these sockets to do the whole job!  Cuts assembly time down by half.

Here is a picture (Canadian penny is the same size as a US penny and a little larger than a Euro-cent).  PS: this is the last year we will have Canadian pennies (boo-hoo!) as the gov't has begun eliminating them from circulating currency.

(click picture to enlarge)

[Ral-Clan]

I paid about $800 cdn way back for a Commodore 8 meg expansion board with 2 megs of ram on it way back. For my A2000.
Paid $240 for 4 megs of ram for my 22mhz GVP accelerator when they were originally released.
Just for reference.

Yeah, I remember I paid (or maybe my parents paid) about a hundred bucks for the 16K RAM expander for my VIC-20 around 1982.  I also think I paid $95 for the A501 512K RAM expansion for my A500 back around 1988 - and that was the best price I could find at the time.

Almost nothing depreciates in value as fast as technology, eh?

The problem with the 1M x 4 DIPs that this Supra needs (to get a full 8MB) is their rarity.  That's what's keeping the value up compared to other chips of the era. Few devices seem to have used them in their DIP format back in the day. If you Google for them, the top 100 results are Amigans looking for these chips. So, unlike the more abundant 256K x 4 DIPS, they have increased in value (if you can even find a source to sell you them).

However, the SOJ version of the 1M x 4 chips seem to be much more common - almost all the old PC memory modules I have from the 486/Pentium days have them soldered on.  They are electrically identical/compatible, but the plastic "package" and arrangement of the pins is different, however.  So while you can probably get them for free, the hard part is that you have to manually unsolder them from the RAM modules and make (or buy) SOJ to DIP adapters.

[Ral-Clan]

The total 8MB has now been installed and has passed the first RAM test!

(click to enlarge)

 

WOW! That was a bit of an ordeal and a challenge! The trickiest part was tracking down bad connections. With the chips all soldered to the adapters, it made for a VERY tight fit for some, and a connection might come loose or a solder joint might break (not visible) if they squeezed against each other during insertion. Amongst the cheaper socket risers I had to contend with bent legs when a misalignment occurred during insertion.

Tracking these mis-connections down over 16 chips (times 20 solder points each) was a bit of a (masochistic) game. I've lost count of how many yellow RAM error screens or red Zorro card diagnostic error screens I've seen over the past three days!

Oh, in the first photo you may notice a layer of electrical tape in between each chip and its neighbour JUST IN CASE one of the connections touched another (the chip sockets on the Supra 500XP board abut each other with no room to spare).

Fortunately, all seems to be working now (knock on wood!).  The chips are snugly inserted into the Supra 500XP and have passed two cycles of RAM testing (I'm going to run them all afternoon on test mode tomorrow).

Sooo....8MB of 1Mx4 SOJs adapted to DIPs, totally from spare parts lying in my parts stash.  I came close to saying this project cost me nothing, but yesterday my de-soldering iron burnt out and I had to buy a new one for $30 - I don't know if I would count that toward the cost.  Even so, I'm still a little ahead.  A lot of labour though!  Was a fun exercise....now I can REST and the family will be shocked to see me again - I've been in my workshop so long!

PS: the pink dots (nail polish) on the chips just indicates to me which way they should be inserted - I was doing things by rote near the end - inserting and removing chips to diagnose problems - and so I was afraid I'd miss the tiny black orientation dimple on the chip if I didn't mark it more obviously.

[Ral-Clan]

Excellent! Glad you got it working. Supreme hackery there! :lol: I love seeing success stories like these..

Thanks!  Also thanks again for the tip about using the DIP sockets as adapter bases.  If you hadn't mentioned that I would still be waiting for the parts from Digikey to start this project.

The only question I would have for anyone who can answer, is why does my Amiga start up sometimes with the RAM fragmentation seen in the mem test screenshot above. Notice that there are three small RAM blocks at the end of the RAM list?

Then at other times (like this morning when I turned it on to start testing) I get less fragmentation (i.e. one large almost 8MB block, the 2M chip RAM block, and just one other small ram fragment as well).

I do recall I made one change since yesterday and today - I put an icon that was "left out" on the desktop "away".  I wonder if this can fragment RAM during boot.