SaRuMan - 64k static RAM for DRAM replacement board

[eslapion]

A replacement board for the 2 DRAM chips on C64 and C64c boards 250466 and 250469 is now available.

This little board replaces the two 64k x 4 bits DRAM ICs with a single static RAM IC. Accordingly it consumes only a trickle amount of power, about 5mA. It also acts as a VSP bug fixer.

The product's name is SaRuMan-64 and it costs 13.25$US or 12 Euros.
Get 20% off when you order 5, 25% off when you order 10 or more. Distributor pricing on 25 units or more.

Shipping cost is the same as with PLAnkton; shipping a small packet (up to 12 units) to the US is 8$. Shipping cost for Europe, Australia and South America is 10$US or 8 Euros.
Get a 10% discount on up to 3 PLAnktons if you order them at the same time.

The product is strictly shipped with antistatic protective packaging. It is covered by a 90 days money back guarantee and a 3 year replacement guarantee afterwards.




What you'll receive.

NOW SHIPPING!

Added:
Ray Carlsen has created a guide on how to install SaRuMan-64 on C64 boards with 8 DRAM ICs. http://personalpages.tds.net/~rcarls...M_REPLACEMENT/
and
How to install SaRuMan-64 on the Plus/4. http://personalpages.tds.net/~rcarls..._REPLACEMENTS/

In the SX-64: http://personalpages.tds.net/~rcarls...AM_REPLACEMENT

A Word of Warning !
Some people have installed 'cheap' or 'Neat looking' PLAs in their Commodore and some of them run at less than 3.7V. This may cause problems with boards 250466 when using this product - genuine Commodore PLAs and good quality PLA replacements signal at 3.7-4.3 volts.
If you have one of these inadequate PLAs and have problems using Saruman-64 on boards 250466, just cut off C204 and it will work fine.

[plazma]

Looks quite similar to my design. I decided to go with easier to solder IC cases for DIY kits.

[eslapion]

Looks quite similar to my design. I decided to go with easier to solder IC cases for DIY kits.
http://www.amibay.com/showthread.php...6-SRAM-for-C64

I had already announced I was going to release this board here (see post #8 ): http://www.amibay.com/showthread.php...-64k-expansion

Posted June 27th. I could not predict somebody would come up with a product which is functionally the same 2 days later. I also announced on June 27 the price would be 15 Euros.

[plazma]

I'm not accusing of copying. That is a logical form of a PCB if you want to minimize the size.
One big point of using these is the fix for the VSP bug. One of my units now pass the VSP LAB test.

- - - Updated - - -

Did you route the address and data lines to their dedicated pins?
I activated pin swap for latch inputs, SRAM address and SRAM data. This allowed me to mix the signals and make a cleaner layout.

You can freely mix the address lines together and data lines together and it works the same

[eslapion]

One big point of using these is the fix for the VSP bug. One of my units now pass the VSP LAB test.

- - - Updated - - -

Did you route the address and data lines to their dedicated pins?
I activated pin swap for latch inputs, SRAM address and SRAM data. This allowed me to mix the signals and make a cleaner layout.

You can freely mix the address lines together and data lines together and it works the same

I see the fix to the VSP bug as a bonus side effect. DRAM is getting difficult to get (although supposedly Abra Electronics has thousands of units in stock) and consumes lots of power.


I did not mix the address lines and data lines because this board can be used in other products where you can effectively replace a portion of RAM with an EPROM. Considering it is a very tedious exercice to rearrange data in a binary file to compensate for mixed data and address lines, I left them in the correct order. This specific version of SaRuMan (there are 3) does not need pins 1 and 18 for the DRAM IC on the left and only pin 18 for the one on the right because all 4 of them are ground connections and very difficult to desolder.


The design for SaRuMan uses TSSOP package for all ICs so and no ICs are above DIP pin contacts which allows it to be installed UNDER the C64/64c mainboard if so desired. This, of course, requires removing the metal shield but in my case, that's no problem as I have removed them all and used nickel paint inside the case as shielding instead.

[plazma]

Almost the same

[eslapion]

@Plazma
I note your schematics uses the 74AHCT1G32 which is too fast for a slow filtered signal like CASRAM is on many C64 boards including the 250466. Your product will crash on these boards. The static RAM you use is also too fast for the slow signals used in Commodore 8 bit computers.

I tried to post changes to my previous post and the forum software systematically erases them.

... finally got it...

Added:
The design for SaRuMan uses TSSOP package for all ICs so and no ICs are above DIP pin contacts which allows it to be installed UNDER the C64/64c mainboard if so desired. This, of course, requires removing the metal shield but in my case, that's no problem as I have removed them all and used nickel paint inside the case as shielding instead.

[eslapion]

SaRuMan-64 is now shipping!

Get a 10% discount on up to 3 PLAnktons if you order them at the same time.

[eslapion]

Just got a new batch of 12 boards!

[eslapion]

Ray Carlsen has used on of my modules to replace all 8 DRAM ICs on an older board 250407.

The 8 DRAM chips needed about 240mA of power in all. The single module now uses less than 5mA.