Amiga 3000 ZIPs DRAM solution ?

[adolescent]

The DIP sockets are only good for 1MB, and can't be used in conjunction with ZIP RAM.  The stock 2MB configuration had 1MB of chip, 1MB of (DIP) fast.  When you updated the fast, you could move the 1MB DIP chips to the chip ram.

adolescent wrote:
The DIP sockets are only good for 1MB, and can't be used in conjunction with ZIP RAM.  The stock 2MB configuration had 1MB of chip, 1MB of (DIP) fast.  When you updated the fast, you could move the 1MB DIP chips to the chip ram.

WRONG!

As long as you put the same type of chip in the ZIP and DIP sockets, you CAN have chip in both type of sockets. As a matter of fact, you will notice that some ZIP sockets have the same UXX numbers as the DIP sockets. That's because they are connected together.

DIP sockets on the fast RAM of the MoBo can accept both 256x4 or 1Mbitx4 chips and fast page mode DRAM chips of both capacities exist in both ZIP and DIP packages.

As long as you don't populate both sockets having the same number and you use the same types of chips, you're okay.

I know so... I did exactly that in my first A3000 15 years ago. It's first 4MByte was 8 1Mbitx4 DIP chips and the last 12MBytes were ZIPs. I did this because DIPs were cheaper than ZIPs.

So, to answer Amiduffer's question: There are 32 ZIP sockets in the 3000's fast RAM section AND 8 DIP sockets. The 8 DIP sockets are just "clones" or "reconnected versions" of the 8 first ZIP sockets. So, if you want 16Mbytes in a 3000, you can either have 32 ZIP chips of 1Mbitx4 or 8 DIP chips of 1Mbitx4 and 24 ZIP chips of the same capacity. Just make sure the part number on your DIP and ZIP chips are the same.

[Zac67]

@eslapion
Take a look at the schematics: there are four CAS and four RAS lines to address the four RAM banks (1 MB or 4 MB each). With PS/2 SIMMs you can either use 4 sockets (one bank each/4 MB SIMMs) or 2 sockets (two banks each/8 MB SIMMs). The latter are even more common and need less soldering.

I think the DIP sockets will only take 256x4 chips, so you're stuck with 256x4 ZIPs, too. No point having 4 MB total.
Are you sure those take 1Mx4, too?

Zac67 wrote:
I think the DIP sockets will only take 256x4 chips, so you're stuck with 256x4 ZIPs, too. No point having 4 MB total.
Are you sure those take 1Mx4, too?

I am absolutely sure! Back then I put chips no. 514400 (by Hitachi, Hyundai, Motorola or OKI) in my 3000. This chip exist in DIP, ZIP or... SOJ packages. And SOJ chips are used on SIMMs.

See: http://www.infinityelectronics.com/crossref.htm

I have a HEAP of 30 pin SIMMs here with the SOJ version of this chip on them. That's why I was interested in buying SOJ to ZIP adapters in the first place. Turns out the adapters are the same price as the ZIPs themselves...

Also, if you look at the cross-reference, it turns out there are many other companies making totally equivalent chips with different numbers. Mitsubishi and TI use number 44400 which I also saw very often on many 30 pin and 72 pin SIMMs too. Not to be outdone, Samsung's 44C1000 is also a frequent find.

All of them 1Mbitx4 chips, all of them fast page mode perfectly compatible with the 3000... if only I could connect them properly...

Take a look at this datasheet: http://www.alldatasheet.com/datasheet-pdf/pdf/31681/TOSHIBA/TC514400AAZ-60.html

Now see how the DIP and SOJ pinout are just about identical.

If anybody has an Amifast or SIMMfonie for sale... I sure would like to make copies of it.

[Amiduffer]

WRONG!

As long as you put the same type of chip in the ZIP and DIP sockets, you CAN have chip in both type of sockets. As a matter of fact, you will notice that some ZIP sockets have the same UXX numbers as the DIP sockets. That's because they are connected together.

DIP sockets on the fast RAM of the MoBo can accept both 256x4 or 1Mbitx4 chips and fast page mode DRAM chips of both capacities exist in both ZIP and DIP packages.

As long as you don't populate both sockets having the same number and you use the same types of chips, you're okay.

I know so... I did exactly that in my first A3000 15 years ago. It's first 4MByte was 8 1Mbitx4 DIP chips and the last 12MBytes were ZIPs. I did this because DIPs were cheaper than ZIPs.

So, to answer Amiduffer's question: There are 32 ZIP sockets in the 3000's fast RAM section AND 8 DIP sockets. The 8 DIP sockets are just "clones" or "reconnected versions" of the 8 first ZIP sockets. So, if you want 16Mbytes in a 3000, you can either have 32 ZIP chips of 1Mbitx4 or 8 DIP chips of 1Mbitx4 and 24 ZIP chips of the same capacity. Just make sure the part number on your DIP and ZIP chips are the same.

Cool. Too bad DIP memory chips are harder to find than ZIPs.

[merlin3d]

Hi guys!!!

I have 16 mb ZIF for A3000! But not use!

[Zac67]

Looking at the pinout, you're completely right - didn't know that yet!

I'm still looking for 8pcs 1Mx4 static column (514402) - just to replace the one bank FP for completeness. ;-)

Software Hut says they have them... 4$ apiece.

I have found adapters A325-ND on Digikey.com that would technically allow you to put DRAM chips 514400 in SOJ format from SIMMs in DIP sockets.

However, the price of these is also quite high and in the case of the 3000, since only the first 8 sockets are connected between DIP and ZIP, that would limit to a max of 4MB...   :-(

[adolescent]

@eslapion

I stand corrected, but at least I was correct about not being able to get 16MB out of DIPs.  (I always assumed that 1Mbx4 DIPS were not usable...).  

I have a AmiFAST for sale.  How much you got?