Minimig PCB run - interest thread

[Dennis]

What could be different and may cause an issue between these SRAM parts is ground/VCC bounce since the PCB is only 2layer and lends itself to a higher inductive volatge drop Ldi/dt on the power and ground connections to the ICs. We can only tell this by testing some of these SRAM parts in an actual 2layer MiniMig PCB.

That can be a problem. On the current board I have had none of such problems however. A friend of mine used to pause Lemmings the whole night and the board was still running every morning. The ground path from RAM to FPGA is pretty wide so inductance is probably not too bad. A single ram chip would be even better though, as no signal routing is necessary on the ground plane.

Dennis

[1NOM155]

Should be better to construct board as was made by commodore? with custom Chips, etc?

and then a Zorro II/III and PCI's ports to add additional and compatible Amiga hardware. :-o

[jkonstan]

Dennis,

For a 2layer PCB, you did a nice job on the layout and helped to keep the blank pcb very affordable.

The concern with the other brands of SRAM (Cypress (CY62157EV30LL-45ZSXI), ISSI (IS62WV51216BLL-55TI),
Renesas (HM62V16514LTTI-5) on a 2layer PCB is the differing levels of Ldi/dt drop for those vs the ST SRAMS. The different brands of SRAM will all draw different amounts of instantaneous current when the SRAM is being accessed (read or write cycle). If you have any pcbs still not fully populated and could validate one of these other brands of SRAM, it would be helpfull.


  :-)

[freqmax]

@Dennis
Will digikey 428-1860-ND do?

Datasheet:
http://download.cypress.com.edgesuite.net/design_resources/datasheets/contents/cy62167dv30_8.pdf

I assumed it had to be SRAM, not SRAM-async.

Maybe it's possible to use the 2'nd layer to add groundplane?

Is the 74HC4060 wired in parallel or serial mode?
Has meaning when looking for crystals (par/ser).

[jkonstan]

The CY62167DV30 1Megx16 SRAM is in a TSSOP 48 pin package, and the 512Kx16 SRAMS are in a TSSOPII 44 pin package. The Cypress 1Mx16 and 512Kx16 SRAMs have different packages and differnet pinouts.

If the MiniMIG schematic and PCB layout were updated for the CY62167DV30 1Megx16 SRAM (TSSOP 48 pin package), the CY62167DV30 1Megx16 Cypress SRAM could possibly be used instead of two of the 512Kx16 SRAMS.
 
:-)

[kolla]

Sorry, Pixie.. just curious if your "it's" in the AROS slogan is a typo or not... "you know it has roots", you know it is roots", or maybe "you know its roots"? :-)

As for minimig, some general purpose connector port/slot for future add-ons would be nice. Personally I would very much like to build it into an old dead A600's case, and would then need some way to hook on the original keyboard.

[mongo]

For a 2layer PCB, you did a nice job on the layout and helped to keep the blank pcb very affordable.

For small quantities, a 2 layer board is much cheaper, but for large quantities (100+) a 4 layer board isn't that much more expensive.

[pixie]

it's as in 'AROS roots'... I was told that it would be it's as opposed to its by an US speaker, but I had that very same doubt as you.

[odin]

"It's" and "Its" are both valid possesives in English AFAIK.

[kolla]

So, can we now also type "he's" instead of "his" and "she's" instead of "her"? :-D

[whabang]

As I said in a previous post:
Google FTW!

[yssing]

I would take atleast 1

For extras...
- Clockport
- A600 RAM expansion, if possible.

Btw, does anyone knows if it is possible to add an A600 accelerator to the minimig?

[Chain]

count me in, 1-2 boards, assembled or not  8-)

[Methanoid]

odin wrote:

"It's" and "Its" are both valid possesives in English AFAIK.

No, they are NOT!!!

[Fixer]

Long time lurker here...

TheMagicM seems to have it right - the project is open source so those handy extras: IDE, clockport, fastram etc may well come in time.

The most important thing however (at the mo) is to get the design Dennis has produced modified (with the suggested fixes) to fit a standard mini/nano-itx case. This way everyone can easily and conveniently enjoy the open source nature of this little masterpiece.

Oh and my congratulations to Dennis btw for finally completing this after 3 years work. You are a saint to this community after a lot of broken promises and general cr*p they have received!

Oh and in regards to the sub-argument, "It's" can not be used for possession - I was assuming it was supposed to be some kind of pun (in that members sig).

[Hans_]

jkonstan wrote:
What could be different and may cause an issue between these SRAM parts is ground/VCC bounce since the PCB is only 2layer and lends itself to a higher inductive volatge drop Ldi/dt on the power and ground connections to the ICs. We can only tell this by testing some of these SRAM parts in an actual 2layer MiniMig PCB.

Sticking a decoupling capacitor right next to the SRAM chip should solve this problem. If the  Most datasheets have some kind of recommendation for decoupling/circuit-layout that you can follow.

Hans