GGLabs DiagROM Configurations
retrofriends.com
I created this page with all my relevant notes regarding the DiagROM software and GGLabs' hardware that uses it. Please feel free to eMail me with any mistakes or useful info. -jon@retrofriends.com
GGLabs Rom and DiagROM: What is it?
DiagROM is Amiga Kickstart ROM software created by John "Chucky" Hertell in 2016, and it needs to be "burned" on to a writable ROM chip that can be plugged into the Amiga's ROM socket. GGLabs makes the F2R16 replacement ROM chip using newer technology, that can be flashed with any compatible image. In the case of the Amiga, you can have any of the original Kickstart ROMs flashed to the GGLabs F2R16, or a custom ROM like DiagROM. You can purchase the F2R16 on eBay with DiagROM installed, and there is also an adapter available so you can flash the F2R16 yourself.
The "OOPS Bug"
The "oops bug" on A500 Rev.5 and older (also A2000 Rev 4.2 and older) motherboards is of course in play when using the F2R16. The F2R16 is natively setup for the newer boards, just like 2.04 and 3.1 kickstart ROMs.
The pin 1/pin 31 hack is needed when using the F2R16 with those other motherboards. I experienced this issue when I ordered the F2R16 for my A500 Rel.5 and it was mistakenly sent without this mod. Fortunately, GGLabs includes
locations on it's board to enable you to easily add the 1/31 hack.
The pin 1/pin 31 hack is needed when using the F2R16 with those other motherboards. I experienced this issue when I ordered the F2R16 for my A500 Rel.5 and it was mistakenly sent without this mod. Fortunately, GGLabs includes
locations on it's board to enable you to easily add the 1/31 hack.
F2R16 Native Configuration (newer Amiga versions)
As shipped without modification, the F2R16 comes set up forA500 Rev. 6 and A2000 Rev 4.3 and newer motherboards without the "oops bug". Changes are made for older motherboards by altering the configurations of four resistor positions, R4, R5, R6, and R7. In most other applications, you would normally see these referred to as "Jumper" positions and would be labeled J4/5/6/7 (although one position, R5, must be connected with a 10kOhm resistor - so that one certainly justifies it's designation). So because they are resistor positions, shorting them without resistance is known as adding a "Zero Ohm Resistor". Isn't that confusing?
Native Configuration for newer motherboards:
(top of diagram to bottom)
R7 Closed
R6 Open
R4 Closed
R5 Open
(top of diagram to bottom)
R7 Closed
R6 Open
R4 Closed
R5 Open
In summary, you don't have to worry about any of this if you only use the F2R16 with newer motherboards. Those who would use DiagROM, would need to work on a variety of versions. I sure do, so read on to learn about the "oops bug" mod and ultimately how to switch back and forth easily.
F2R16 Older Amiga Motherboard Modification
(A500 Rel.5 and A2000 Rel.4.2 and older)
(A500 Rel.5 and A2000 Rel.4.2 and older)
Here all 4 positions have been altered for older motherboards. By the way, the reason I drew some "switch" representations of the closed/open connections in the white area is because that is the direction we are heading. Note the places to cut the traces.
Altered Configuration for older motherboards
(top of diagram to bottom)
R7 Open (cut trace)
R6 Closed (short connection)
R4 Open (cut trace)
R5 Closed with 10kohm resistor
(top of diagram to bottom)
R7 Open (cut trace)
R6 Closed (short connection)
R4 Open (cut trace)
R5 Closed with 10kohm resistor
So to make the F2R16 switchable, read on...
F2R16 Switchable Modification
As it turns out, a simple DPDT switch can do the job, because there is a common conductor in each case. R7 and R6 share a common conductor: the trace to A17. R4 and R5 share a trace too.
Pin 31 to the motherboard is also shared on R6 and R5, thus making it possible to cross-connect the two corner conductors of the switch.
Pin 31 to the motherboard is also shared on R6 and R5, thus making it possible to cross-connect the two corner conductors of the switch.
One more thing... I was told by a representative of GGLabs that the resistor probably can be left in place for any revision, but that he hasn't tested it. I have decided to test this theory and I will update this information as needed. The F2R16 does boot on an Rel.6 A500 motherboard with the resistor in place, and I will do more testing. The following configuration is with the resistor in place and not switched, and is actually how I have mine set up.
F2R16 Switchable Configuration with R5 resistor unswitched
That's it for now. I will be experimenting with the DiagROM more in the future. Fortunately I have kept all my bad Amiga chips, so the results should be interesting. I do not have any bad Amiga 500 memory chips, however, so if you have any and are willing to send me a couple please email me. jon@retrofriends.com