EconoSimm: Really cheap custom rom for your SE/30. Open source!

[K55]

My house is surrounded by snow and fallen trees so I had some free time to throw this together.

I like the idea of having a custom rom in my se/30 because a 10 minute ram check is tedious every time I boot.

However seeing that there are no open source projects out there for a rom-simm, and the next best thing requires an expensive programmer for no reason :^).

I call this project "EconoSimm" because the total price of a unit is around $15. The major benefit comes from it using standard PLCC flash chips.

So while the max memory is restricted to 2MB/16Mb anyone with a standard programmer can flash the EEPROMS.

It's open source for everyone to enjoy

Basically: Custom roms for less than the cost of a tank of gas

Github link: Click here!

Board:



Totally not thrown together in gimp render:



Schematic:

 

[tt]

I thought the original design dougg3 made used standard eeprom chips that you can pop in and out. I believe that design is open source.

There was someone who didn’t know what they were doing trying to undercut his later 8mb design, which is somewhat difficult to make for a hobbyist anyway, but it didn’t materialized. However, that one requires a specialized programmer. I think that design is also open to make yourself, but the chips are hard to find for a reasonable price.

 

[trag]

On this kind of design, I would recommend either making the sockets through hole, or putting two chips on the back and two chips on the front of the board.    It's almost impossible to hand solder the surface mount sockets, because of the center plastic piece, most folks aren't going to solder paste and toaster oven a board at home.   Spreading the chips on both sides of the board leaves a lot more room between the chips for soldering.

So, make it through-hole, folks must use sockets, but they're pretty easy to solder.  

Or put the chips on front and back, and there's plenty of space between them for soldering the chips directly to the board, but not such a good design for a socketed board (because of difficulties with two sided solder toasting).

 

[Trash80toHP_Mini]

Nice! Love the rendering.

I got a tube (32 pieces?) of thruhole sockets for the 20pin version of that PLCC socket on eBay. It might be worthwhile tracking that part down somewhere. Muuuuch easier!

Wish some folks would pick up the ball and run open source with my internal Pi Programmer/Rom SIMM Emulator proposal. :-/

 

[K55]

I never really had an issue with PLCC sockets, you just cut out the center and solder it like this:

The main issue with through hole PLCC is that the pin arrangement is horrible for multiple in line chips. It's possible but very very ugly.

 

[K55]

Speaking of ugly..



BEHOLD THE VERSION FOR THRU HOLE PURISTS

MINIMALLY AUTOROUTED

ADHERES TO SOME SIGNAL INTEGRITY STANDARDS

UPLOADED TO GITHUB

MY CAPS LOCK IS STUCK

 

[techknight]

Autorouter? I dont think I have ever used an autorouter when laying out PCBs. I am sure powerful packages like Altium, etc have powerful autorouters, but the one in eagle is awful. at least thats been my experience. 

My portable RAM card was all done by hand.

 

[techknight]

MY CAPS LOCK IS STUCK

Go to the closet and grab a hammer. That fixes it every time. ;-)

 

[K55]

Autorouter? I dont think I have ever used an autorouter when laying out PCBs. I am sure powerful packages like Altium, etc have powerful autorouters, but the one in eagle is awful. at least thats been my experience. 

My portable RAM card was all done by hand.

The prorouter in eagle is nice enough to get the job done. I use it for isolated runs of a few traces when I've handfit most of a board to speed up work.

 

[croissantking]

Necropost...

I'm looking to get some of these Econosimms made up, and I just wondered if for the PLCC chips, there is a minimum speed requirement? (e.g. 70ns, 90ns, 120ns, etc.)

 

[zigzagjoe]

AFAIK the stock ROMs are slow as dirt (170ns) so anything modern ought to work.

 

[Phipli]

Yeah, we worked out that the IIci stock ROMs are 200ns. Slow as walking through waste deep treacle.

 

[croissantking]

Yeah, we worked out that the IIci stock ROMs are 200ns. Slow as walking through waste deep treacle.

Love the analogy.

 

[croissantking]

I got some of these econosimms made up.

I'm looking at flashing "iisi+romdrv0.9+nomem+nosum+img.bin" from http://synack.net/~bbraun/macromboot.html.

How would I successfully split the ROM file into four parts to go on each of the chips?

 

[joshc]

How would I successfully split the ROM file into four parts to go on each of the chips?

There are online tools, GUI programs for various OSes and the Unix program split for this.

 

[robin-fo]

You can do it with Python in just a few lines of code. I did this to flash a 650 ROM onto a PurpleROM

 

[croissantking]

I just wondered if the .bin file needs any sort of special interleaving for the SE/30 that I would have to specify when doing the split.

 

[luRaichu]

AWESOME, I love projects like this!
While on the topic: Are there new, off-the-shelf chips you could utilise for PowerBook RAM? In place of the discontinued and elusive 658512LTT-x ICs?

 

[croissantking]

Well the best person to ask would be SiliconInsider who actually makes these cards new: https://www.tindie.com/products/siliconinsider/purpleram-10mb-memory-module-for-powerbook-160-180/

On the page it says:

Each memory modules has been professionally hand assembled using new old stock Hitachi 50ns SRAM memory chips. Modules are guaranteed to be functional and have been fully tested in a vintage PowerBook machine.

Low power: Instead of using original pseudo-static RAM (PSRAM), my modules are using more costly real static RAM (SRAM) which do not need refresh and use a third of the power used by original PSRAM.

In the photo the chips are 628512BLTT5 with date code 0103. Maybe you can find a supply of these on UTSource or similar. You'll have to do some digging.

 

[luRaichu]

In the photo the chips are 628512BLTT5 with date code 0103. Maybe you can find a supply of these on UTSource or similar. You'll have to do some digging.

I did Google this IC and get quotes from various distributors. The number at the end of the chip's part number indicates latency (in ns I think??). It comes in speeds of 85, 10, 8, maybe 5.
I have a list of quotes on this chip, not sure if I should share it here.