/GottaGoFastRAM

8MB Autoconfig FastRAM for Amiga 500/1000/2000/CDTV

Primary LanguageVerilogOtherNOASSERTION

GottaGoFastRAM 8MB Autoconfig Fast RAM

This is an 8MB Autoconfig Fast RAM for Amiga 500/1000/2000/CDTV based on mkl's mem68k
It's small size allows it to be stacked on top of an ide68k board
Rather than use the original mem68k Abel code I have written a new memory controller in Verilog

PCB Assembled

Table of contents

  1. PCB Ordering
  2. Mounting Options
  3. Cfgin/out
  4. Jumpers
  5. CDTV
  6. Timing Diagrams
  7. Bill of materials
  8. Known Issues
  9. Experimental firmware

Ordering PCBs

I recommend ordering the PCB with a 0.6 or 0.8mm thickness if you intend on stacking with an ide68k or mouting using a DIP socket/machined pin strips.
If you are going to mount using the socket pins and not stacking with an ide68k I'd recommend going with the usual 1.6mm to reduce flexing.

Mounting options

  1. Can be soldered to the bottom of a machined pin socket/machined pin strips (will require some cutting of the dip socket to fit the caps/ferrites near the plastic)

2. Can be soldered to socket pins and stacked with an ide68k

Cfgin/out

These pins allow you to insert the memory module into your autoconfig chain.
If there are no other autoconfig devices in your system you can just leave these unconnected otherwise you will need to either connect CFGOut to the CFGin of the first device in your existing autoconfig chain, or connect CFGIn to the CFGOut pin of the last device in your existing autoconfig chain.
In the Amiga 2000 you can connect CFGIN to U606 Pin 8 which will add the device to the end of the chain but NOTE: This takes up the config signal for the leftmost slot (CN601) so do NOT install a Zorro card there

You can also connect cfgin and cfgout with a jumper to disable the device temporarily

Jumpers

J1: Cfgin pull up/down (You will probably want to leave this at default unless you know what you're doing)
J2-3: Bridge these if you have not fitted the buffer U4

CDTV

The CDTV's DMAC takes up the first autoconfig slot, so if you intend to use this with a CDTV use the CDTV specific .JED file to program the CPLD

If you have a Rev A or Rev B (not B1) board you will need to apply a small mod for CDTV compatibility

Timing Diagrams

Read Cycle
Write Cycle

Bill of materials

Component Location QTY Link Remarks
4Mx16 3V DRAM TSSOP - K4E641612D or GM71VS65163 U3 1 - eBay/Aliexpress etc.
XC9572XL-10VQ64C U1 1 Mouser
DigiKey
74LVC2G17 TSSOP-6/SOT-363 U4 1 Mouser
DigiKey
AP2210N-3.3 SOT-23 U5 1 Mouser
DigiKey		 Maybe can be substituted with MCP1703AT-3302E
74LVC245N TSSOP U6,U7 2 Mouser
DigiKey		 Can be substituted with SN74LVTH245 or SN74LVCR2245
Ferrite Bead, 1206 package FB1, FB2 2 Mouser
DigiKey		 Can be substituted with 0 Ohm 1206 resistors
10K Resistor, 0603 R1 1 Mouser
DigiKey
0.1uF Ceramic Capacitor, 0603 C1,4-13 11 Mouser
DigiKey
4.7uF Ceramic Capacitor, 1206 C2 1 Mouser
DigiKey
10uF Ceramic Capacitor, 1206 C3 1 Mouser
DigiKey
Socket pins Pins 64 Aliexpress Use these if stacking with an ide68k module
64-Pin DIP socket - machined pin Pins 1 Mouser If not stacking with ide68k - pcb can be soldered to bottom of this flush with the plastic

Known issues

  1. Rev A & B - Incorrect voltage supplied to U4 causes incompatibility with CDTV. Fixed in Rev B1 but you can rework Rev A or B boards by following the instructions here

Experimental Firmware