2MB Chip Upgrade: Hacks and Ideas

[AndyLandy]

Hello my fellow AmiBayers, I have split this disscussion from one of the sales threads. There are some cool ideas and I hope that we can discuss what would make the ultimate CHIP upgrade adapter

Anyway, I shall leave the thread for Andy to start -

Because of the high costs, I look for some selfmade solutions. But I guess there's nothing...

Oh, there are homebrew solutions to the problem. But you need to track down an 8372B or 8372AB Agnus part, desolder the ChipRAM and replace with higher-density chips and add some extra signalling wires to address the second MB of Chip. I found a HOWTO on the web once, but can't remember where. If I find it again, I'll link it here.

 

[ThunderStorm81]

I found something, unfortunately only in german, but I will try this one asap.

http://www.forum64.de/wbb3/board169...-2-mb-chip-ram-im-amiga-2000-rev6-f-r-5-euro/

---------- Post added at 11:47 ---------- Previous post was at 11:23 ----------

I saw I need eight 4*1024 (4MB) RAMs, anybody has an idea where to get it?

 

[Roman78]

I want to try the same. Good think that i can german

You can remove those chips from other old memory.

http://www.pitsch.de/stuff/amiga/a20002mb/index.htm

If you want i can try to translate, but my english is not the best.

Edit: forget the last sentence... u from germany

 

[storhemulen]

Digging up an old thread here...

The mod described in that german link seems to be for rev 6 boards only. Does anyone know if it is possible to modify a rev 4.x board in a similar (or the same) way?

 

[ryckart]

Chipram Hack

Chipram Hack

Because of the high costs, I look for some selfmade solutions. But I guess there's nothing...

Oh, there are homebrew solutions to the problem. But you need to track down an 8372B or 8372AB Agnus part, desolder the ChipRAM and replace with higher-density chips and add some extra signalling wires to address the second MB of Chip. I found a HOWTO on the web once, but can't remember where. If I find it again, I'll link it here.

This may be what you are looking for:

http://www.mylinuxisp.com/~jdbaker/oldsite/documents/2MBAgnushack_v1.4.txt

 

[rkauer]

I'm still in the process of validating this hack for the A500. Only now I get a 2Mb Fatter Agnus from a dead A3000 :crying:

Now the search for the 1024 x 4 begins... :blased:

 

[Zetr0]

Hmmm

I have read that explanation / how-to a few times, the hardest part is the 8372B or 8372AB 2MB Agnus - the re-routing and wire-wrapping is just a formality and time consuming.

A much better method would be to design a small PCB with 1MB of Memory on it - either organized as

1x 512x16
2x 256x16
2x 512x8


Personally I would use 2x 256x16 as in the A600, these would be easy to solder and are found on virtually any old ISA/PCI 2/4MB Graphics card.

to be fair any chip(s) with a speed of 100ns or faster (see lower) would be adequate

I promised myself that I would develop one of these adapters on the cheap utilising a pin-socket-plug and a socket for a 2MB - 8375 - 390544 (obviously pin corrected), it would need a simple PAL/GAL for it to negotiate with GARY to use the 1MB of RAM on Card and the 1 MB of RAM on the motherboard.

sounds more complicated that it reads.

 

[AndyLandy]

OK, given that RAM is pretty inexpensive these days, would it be any easier to design a the PCB to have all 2MB of Chip RAM on it and ignore the stuff on the motherboard entirely? It'd save a lot of motherboard rework at the very least, would allow you to use the adapter in 512k-chip Amigas and could potentially let you still keep 512k Ranger RAM on top of the 2MB Chip RAM. I guess you'd probably still need to play with Gary for your assertions though.

 

[Zetr0]

@Andy

The problem with that would be memory shadowing, and if the adapter RAM latches a data update where the motherboard RAM didn't then you wil have serious problems with garbled data.

There is practically no benfit to shaddowing the RAM in such a way, but the idea of MORE ram in the Ranger area (say 1.5MB) of it (thus making a 2.5MB board) might not be a bad idea.... this could quite comfortably work for all a basic A2000 re 4.5 + to have 2MB CHIP + 1.5 MB (slow) OTHER RAM - a pefect addition for WHDLoad =)

while it would be slow due to CHIP speed contention, it would aleviate the limits of a lot of systems - such like the humble A500 rev3 / rev 5 and 6a, as well as the CDTV if the adapter was designed as such from the ground up. Also a jumper to turn off the Ranger RAM off - (for those with REAL fast RAM additions to their kit)

The only problem being, the sourcing of the Agnii =/

 

[AndyLandy]

@Andy

The problem with that would be memory shadowing, and if the adapter RAM latches a data update where the motherboard RAM didn't then you wil have serious problems with garbled data.

There is practically no benfit to shaddowing the RAM in such a way, but the idea of MORE ram in the Ranger area (say 1.5MB) of it (thus making a 2.5MB board) might not be a bad idea.... this could quite comfortably work for all a basic A2000 re 4.5 + to have 2MB CHIP + 1.5 MB (slow) OTHER RAM - a pefect addition for WHDLoad =)

while it would be slow due to CHIP speed contention, it would aleviate the limits of a lot of systems - such like the humble A500 rev3 / rev 5 and 6a, as well as the CDTV if the adapter was designed as such from the ground up. Also a jumper to turn off the Ranger RAM off - (for those with REAL fast RAM additions to their kit)

The only problem being, the sourcing of the Agnii =/

Is the Chip RAM addressed from anywhere else other than Agnus? I'm advocating completely ignoring the Chip RAM on the motherboard. Just pretend it's not there, don't let Agnus even know it exists.

Now, if you could bolt on 1.5MB of Ranger RAM as well, that'd be a really exciting prospect! Being able to disable it would be nice, but if it's given a priority that's only marginally higher than the Chip RAM, there'd be little point in doing so.

As for sourcing Agnii, the world is full of dead A500+ motherboards. If we could create an adapter that gives 2MB ChipRAM, you'd only need to salvage the 8375 Agnus and the Super Denise from the Plus board and you could promote any old A500 board to 'Plus' status. Well, except for the clock, but let's face it, that wretched clock is the source of so much A500+ misery in the first place!

What d'you reckon, oh almighty wizard? Can we do it?

 

[Zetr0]

/Zetr0 puts on thinking cap and wonders why its pointy and has a 'D' on it =)

Is the Chip RAM addressed from anywhere else other than Agnus? I'm advocating completely ignoring the Chip RAM on the motherboard. Just pretend it's not there, don't let Agnus even know it exists.

Unfortunately no, as they share the same pathway for access / latching, while the memory might well be on the PCB its data path is shared on the motherboard, as is the higher 1MB of RAM as well its only the RAS/CAS lines that seperate it latching.

One could remove the memory from the motherboard though, however that is a little hardcore for an upgrade, a more logical solution would be to just multiplex 256k x 16bit RAM banks with whats on the motherboard.

Now, if you could bolt on 1.5MB of Ranger RAM as well, that'd be a really exciting prospect! Being able to disable it would be nice, but if it's given a priority that's only marginally higher than the Chip RAM, there'd be little point in doing so.

Interms of priority it would use the Ranger (Other Mem) RAM first, before hitting the chip ram allocation, however in terms of speed they would be identical, since it uses the CHIP bus to acceess data.

As for sourcing Agnii, the world is full of dead A500+ motherboards. If we could create an adapter that gives 2MB ChipRAM, you'd only need to salvage the 8375 Agnus and the Super Denise from the Plus board and you could promote any old A500 board to 'Plus' status. Well, except for the clock, but let's face it, that wretched clock is the source of so much A500+ misery in the first place!

What d'you reckon, oh almighty wizard? Can we do it?

can we!?.... hmmmm I really want to do it, while it might read difficult, shematically and logically it should be straight forward to implement. A while back I promised myself an attempt at allocating RAM on the CHIP buss outside the 2MB Chip Barrier, I also promised my self that I would attempt a 2MB CHIP upgrade having 2MB of Memory onboard, it would be alocatable to

1MB chip 1MB other
1.5MB Chip 0.5MB Other

I have a rev6a here that needs to feel love again... so when I get r3play outa the way... then I might just hackon with this... although I do have a couple of software projects that I need to startup as well....

sigh... even with an infinity of time, I would be infinately busy doing everything else LOL

 

[storhemulen]

One asks a simple question, and suddenly all the wizards come out from their hiding and starts conjuring up new designs.

 

[Zetr0]

One asks a simple question, and suddenly all the wizards come out from their hiding and starts conjuring up new designs.

Ohhhh so its YOUR fault is it!?


As an update, I spoke with Andy on the phone, and in discussion we developed a really cool idea.

• 4MB onboard (this could be done in single cheap 16bit chip)
• Highly configurable pending installtion target

• 1MB CHIP & 3MB Other mem
• 1.5MB CHIP & 2.5MB Other mem
• 1MB CHIP & 0MB Other mem
• 1.5MB CHIP & 0MB Other mem

• Plugs in the Agnus Socket
• Has a socket for an 390544 8375 2MB Agnus
• A CPLD to handle Memory Bank (256x16bit) Latching
• *Software (ADDMEM) to add the remaining (upto 3MB) RANGER memory

*its quite likely that this ADDMEM with the Right CPLD could be done in hardware

The idea being to primarilly make an adapter with a target price £30 (not including an Agnus) that can add 1MB or 1.5MB of CHIP pending its host.

The RANGER addition is just a bonus for limited system to take advantage of- like the CDTV and or A500/A2000 - thus the can utilize software that needs more memory and even WHDLoad if they have a mass-storage, like in the case of the CDTV

 

[AndyLandy]

Having a jumper to toggle between 1.0 and 1.5MB of ChipRAM solves the problem quite nicely. This pleases me greatly! Essentially, I'd like to take away as much hard work from the end user as possible. Even the r6a "1MB ChipRAM hack" is asking a bit much. Being able to just jumper the board makes life much easier.

Finding enough room to wedge in a bunch of pseudo-FastRAM is a bit harder. The first 1.5 is easy, since there's already 1.5 MB allocated to Ranger RAM. There's also an unallocated 256k above it, so a contiguous lump of 1.75MB RAM could be allocated.

Finding more space is possible, but might be a bit trickier:
Judging by the A500 memory map, it looks like there's plenty of unused space in the 24-bit address range for us to wedge a bunch of pseudo-fast RAM into: http://en.wikipedia.org/wiki/Amiga_500#Memory_map

There's a bunch of places that are listed as "reserved" but without really clarifying what they're reserved for. I suspect some of them are for Zorro II autoconfig*, so aren't really free to be recycled, but I'm sure there are some places where the address range was 'reserved for future use' and is still unallocated. It looks like I'm probably going to have to sit down and collate all the different versions of the memory map and work out what actually is spare. At the very least, everything that's not a CDTV could use the 512k "Extended ROM" space.

If anyone out there has a BASEBoard expansion in their A500. I'd love to hear from you! Any chance you could fire up Sysinfo and let us know what memory range(s) it allocates it's FastRAM into?

*Not all Zorro II boards sit within the 8MB "Zorro II" range. That's where RAM goes, and some other large things, but there's somewhere else on the memory map where small things like I/O boards are allocated 64k/128k of address space.

 

[SpeedGeek]

@AndyLandy
I would use caution in adding memory to "Reserved" areas of the Amiga memory map. Sure it looks like there is good potential for memory expansion in this area but the address decoding logic (or lack there of) leaves mirror images in many of these areas near the Custom Chip registers, Zorro2 I/O space, RTC and ROM's. Indeed, this is precisely why you can use a 1MB ROM on a A500 or A2000.

 

[AndyLandy]

@AndyLandy
I would use caution in adding memory to "Reserved" areas of the Amiga memory map. Sure it looks like there is good potential for memory expansion in this area but the address decoding logic (or lack there of) leaves mirror images in many of these areas near the Custom Chip registers, Zorro2 I/O space, RTC and ROM's. Indeed, this is precisely why you can use a 1MB ROM on a A500 or A2000.

Do you mean can or can't use a 1MB ROM? That's pretty annoying! But typical of C=, I guess...

Still, we can still have our 1.5MB of ChipRAM and 1.5MB of RangerRAM. It's still a lot better than a kick in the teeth.

 

[SpeedGeek]

Do you mean can or can't use a 1MB ROM? That's pretty annoying! But typical of C=, I guess...

Still, we can still have our 1.5MB of ChipRAM and 1.5MB of RangerRAM. It's still a lot better than a kick in the teeth.

Yes, I mean can use a 1 MB ROM. The second 512K of ROM is properly addressed by the CPU but Gary sees this as a mirror image of the first 512K and generates a ROM chip select accordingly. This doesn't work on an A3000 or A4000. Sometimes the sloppy C= design practices work in your favor!

Also, the 1.5MB of "Ranger" space is the one safe place to add extra memory. It was originally used for the 2nd 512K of "Slow Fast" memory for A500's or A2000's which had a 512K Fat Agnus chip.

 

[AndyLandy]

/Zetr0 puts on thinking cap and wonders why its pointy and has a 'D' on it =)

Is the Chip RAM addressed from anywhere else other than Agnus? I'm advocating completely ignoring the Chip RAM on the motherboard. Just pretend it's not there, don't let Agnus even know it exists.

Unfortunately no, as they share the same pathway for access / latching, while the memory might well be on the PCB its data path is shared on the motherboard, as is the higher 1MB of RAM as well its only the RAS/CAS lines that seperate it latching.

During one of my "Poke around on Amiga.Resource" sessions, I discovered this curious little thing: http://amiga.resource.cx/exp/topchip

According to The Resource:

• 2 MB Chip RAM on board - disables the motherboard Chip RAM
• four 1M×4 ZIPs
• requires 2 MB 8372B Agnus
• connects to the Agnus and Gary sockets
• can be switched by software between 512 kB, 1 and 2 MB if used with Black Knight's No More Switches

Disables the motherboard Chip RAM? Software switchable between 512kB/1MB/2MB? Now that's quite tasty. I wonder how it works.

 

[Azryl]

Wow, software selectable Chip ram, so it *IS* possible to disable the onboard chip ram. Makes your proposed upgrade very interesting!

I have an Adspeed 16mhz Cpu turbo that needs some extra ram

Az

 

[SpeedGeek]

On board chip ram can be disabled by simply keeping the RAS/CAS signals negated. They are normally asserted low so a couple of pull-up resistors could do it. Technically just keeping CAS negated would do the trick but RAS negation will add a little extra insurance to this type of hack. This also means that Fat Agnus' RAS/CAS must be disconnected from the on board chip ram!