128megs on a CSA Derringer 030

[Metalguy66]

I will definitely try it. Now i am using 64MB SIMM which D3 detects as 16MB.
The system is stable with it.

Do you think I will get 64MB with this hack?

The SIMM is single sided with 8 chips on it. The chips are MT 4LC16M4H9-5D.

http://pdf1.alldatasheet.net/datasheet-pdf/view/75891/MICRON/MT4LC16M4H9DJ-5.html

Well, it depends actually on how it is getting the 16meg. But like I said, there's no reason not to perform the mod. It won't change the way your derringer works with existing SIMMs. All it does is open the possibilities of using SIMMs that have a full 12bits of base addressing.

Now back to the question of the RAM banking. Best case scenario, you could try several ranges and see which one works.

With a single sided SIMM I would *THINK* that its only using 2 RAS signals, but seeing full 11bits of base addressing and so it's getting 2 banks of 8megs. If that is the case, after the hardware mod is done, you should be able to get 2 banks of 32megs each by doing something like:

Addmem $08000000 $0A000000 checkmem 32bit
Addmem $18000000 $1A000000 checkmem 32bit

-or-

Addmem $08000000 $0A000000 checkmem 32bit
Addmem $28000000 $2A000000 checkmem 32bit

If the simm is wired differently, it could work with the following and get 4 sections of 16megs:

Addmem $08000000 $09000000 checkmem 32bit
Addmem $18000000 $19000000 checkmem 32bit
Addmem $28000000 $29000000 checkmem 32bit
Addmem $38000000 $39000000 checkmem 32bit



The datasheet you linked shows that those chips do have the A11 address line, so I would guess one of the first two scenarios to be the case.

When testing, disable D3 in your s:startup-sequence, so that no 32bit fastram is added to the system at bootup. Then, open a shell and try the above Addmem commands with the checkmem option invoked. If any section of ram isn't going to work, it will return an error message within a few seconds. If it doesn't, the system will appear to be locked up while it tests that section of RAM for several minutes, but eventually, it will return you to the AmigaDOS prompt and add the ram to the system (you'll see "other memory" increase at the top of the workbench screen.) After you've done all your testing, reenable D3 in the s:startup-sequence, plus add an Addmem command for each additional ram bank that D3 doesn't find, and this time, no checkmem option. (D3 "finds" the first bank, located at $08000000)

Hope this helps. Good luck![/b]

[Metalguy66]

I will definitely try it. Now i am using 64MB SIMM which D3 detects as 16MB.
The system is stable with it.

Do you think I will get 64MB with this hack?

The SIMM is single sided with 8 chips on it. The chips are MT 4LC16M4H9-5D.

http://pdf1.alldatasheet.net/datasheet-pdf/view/75891/MICRON/MT4LC16M4H9DJ-5.html

The data sheet you linked shows that the DRAMs on that SIMM have a full 12bits of adressing. So basically, this SIMM is a single sided version of the 128megger. So youve got A2 - A23 (11bits of muxed adressing to the SIMM),A24 uses various CAS signals to determine which 4 of the 8 chips we are talking to for any given 32bit access, but with only single sided, you are missing 2 of the 4 RAS signals, so A25 is nullified. So, yeah, we get to 16meg, but not 32meg. My hack adds A28 and A29 (the 12th bit of muxed adressing to the SIMM)which effectively adds 3 more identicle "banks" using the "upper halves" of all the chips.

Translation: If it's gonna work, here's how it will work:

4 sections of 16 megs each, spread 256megs apart in the adress space.

Addmem $08000000 $09000000 checkmem 32bit
Addmem $18000000 $19000000 checkmem 32bit
Addmem $28000000 $29000000 checkmem 32bit
Addmem $38000000 $39000000 checkmem 32bit


When testing, disable D3 in your s:startup-sequence, so that no 32bit fastram is added to the system at bootup. Then, open a shell and try the above Addmem commands with the checkmem option invoked. If any section of ram isn't going to work, it will return an error message within a few seconds. If it doesn't, the system will appear to be locked up while it tests that section of RAM for several minutes, but eventually, it will return you to the AmigaDOS prompt and add the ram to the system (you'll see "other memory" increase at the top of the workbench screen.) After you've done all your testing, reenable D3 in the s:startup-sequence, plus add an Addmem command for each additional ram bank that D3 doesn't find, and this time, no checkmem option. (D3 "finds" the first bank, located at $08000000)

Hope this helps. Good luck!

[JanciB]

I have desoldered U17. Pin 12 appears to have no trace. Can I cut the traces on pin 13 and 14, so I don't have to lift them? Like on the image that I have attached.

[Djole]

Very nice mod. Is there any chance to make something like this for other boards like a1200 turbo cards which support only 8megs of ram ?

[Metalguy66]

JanciB: I have desoldered U17. Pin 12 appears to have no trace. Can I cut the traces on pin 13 and 14, so I don't have to lift them? Like on the image that I have attached.

Yep.
As is customary, 13 and 14 are inputs so they are grounded if unused. 12 is the output so it is just left floating.. But yeah, you can cut the 2 traces to 13 and 14 and then when you replace the IC, you can solder all the pins down rather than lifting 12,13,and 14.

[Metalguy66]

Very nice mod. Is there any chance to make something like this for other boards like a1200 turbo cards which support only 8megs of ram ?

If you send me an A1200 and said "turbo board" for experimentation purposes, I'll gladly look into it.

[JanciB]

I just finished the mod. It's working!

Added mem with Addmem. Got 64MB with my 64MB simm.

Avail shows largest block 16MB. I think that's normal.

Thanx Metalguy66!

JanciB

[Oldsmobile_Mike]

Sweet! Someone should start a Kickstarter to get @Metalguy66 some of those A1200 expansions. We all know the A1200 can address more than 8MB through it's expansion slot, so why the limit on so many of the standard ram/FPU/clock combo cards?

Or is it because of the "EC" nature of the A1200's 68020? I can't recall off-hand, does it only have 24-bit addressing or something?

Now we just need you to make a mod to allow GVP accelerator cards to use anything other than those damned proprietary GVP SIMM's! :hammer:

[Plaz]

Nice work. You wouldn't happen to have similar schematics for the mega midget racer would ya?

Plaz

[QuikSanz]

@Oldsmobile_Mike,

You ain't whistling in the wind here, My GVP Combo would love more than 16Mb! At least til we get a fast FPGA for the A2000!

Chris

[Metalguy66]

In response to those asking about the possibility of coming up with an "easy hack" to expand the 32bit fastram on various other accelerators:

It totally depends on the design of the accelerator board in regards to How they are addressing the dram. The CSA Derringer's design just begs to be "expanded". The one extra dram address line that exists on a 72pin SIMM, and that the Derringer's design doesn't employ can  be easily generated by simple direct cpu adressing. That isn't always the case, depending on how they are getting the "8 megs" or "16 megs" on some of these expansions. Chip/Bank selection on larger SIMMs depends on the use of multiple CAS and RAS signals (up to 4 of each) which must be generated with specific timing requirements. The Derringer already uses/employs all of these. The addition of these to a design which does not employ them would require additional logic, and almost certainly changes to logic in the existing design. In the case of most accelerators, this means not only adding some ICs to drive the extra signals, but also reprogramming of existing GAL/PAL/CPLD chips to accommodate this.

As far as the Derringer hack goes.. heh. You can thank Steve Kelsey (He also designed the Warp Engine 040). Anyone looking at the Derringer's design would immediately see what I saw. Kind of like a bonus "easter egg" for the future.. In 1991, even a 32meg SIMM was outrageously priced and more ram than most people could find a way to use. But, since 128meggers are available and cheap nowadayze, its nice that the Derringer's design "leaves that door open" for us.

[Plaz]

Since CSA did both the Deringer and M.M.R, I was hoping designs would be similar and most of all you would have docs.

I could add logic if needed, but I'm hoping to cheat by avoiding the reverse engineering steps to save time.

Plaz

[Metalguy66]

Ok, regarding the CSA Mega Midget Racer specifically:

Well, no doubt, if you were to send me the board, I could come up with a scheme to expand it, but theres really no way to do an "easy hack" like the Derringer has. I mean, to add a SIMM to that thing, you are talking 50+ solder points. To "piggyback" or similar, using discrete ramchips would involve even more. Those are most likely 1megx4 ZIPP drams.. So 10bits of address and then some scheme of discrete CAS/RAS signals used to determine which set of 8 chips is being accessed at any given time. You may be able to remobve all the zips and do something similar to what the Amifast ZIPP-SIMM adaptor does. Id have to see the exact access scheme being used in order to say "yes or no" on that. But assuming it is possible, and depending on how much of the 72pin SIMM access standard could be utilized that way, you may then be in a similar situation to the derringer where you could then start making RA10 and RA11 by simply muxing higher CPU address lines and thereby quadrupling total ram with each. This depends on quite a few very big "IFs".  In any case, you are talking about a much more involved project than what is required on the Derringer.

[Oldsmobile_Mike]

Hi @Metalguy66:

I'm just going to throw this idea out there, hopefully it's not too crazy.  

Most A2000-style GVP accelerators can accommodate up to 64MB of ram.  At least, their '040 boards.  But to do this, you need four of the proprietary 16MB GVP SIMM's.  Most people only have the 4MB SIMM's.  Your above post gave me this idea:  since the accelerator card itself can already support the additional memory, do you think it would be possible to piggyback additional ram chips onto the 4MB modules to "make them into 16MB modules"?  Since the actual 16MB modules are rarer than hen's teeth, apparently.  

http://amiga.resource.cx/exp/gforce2040

I'd be glad to get a 4MB module to send to you, or send you high res photos of the chips, if you think that would help?

Just want your opinion, since you're the expert on this stuff.  Thanks!  

[Metalguy66]

1.) I'd need the A2000, the Accelerator, and the RAM.
2.) It would be much more productive to just go ahead and wire in 72pin SIMM sockets. Less connections, less of an unorthodox "ass-rig" and if the dram ever went bad, you'd be able to replace the SIMMs.
3.) You are talking about a VERY involved project. Not something worth writing up for others to easily attempt.
4.) Yes, any machine with at least a 68020 has a 32bit data bus and at least 4 gigs of physical address space. Its just a matter of designing the dram control/address circuits (or modding existing ones) to get the dram on the bus.
5.) I'd be willing to look at anything, and even attempt anything if price is no object, but unless theres already a standard simm socket there, the end result is not gonna be an easily repeatable "hack".

[Oldsmobile_Mike]

1.) I'd need the A2000, the Accelerator, and the RAM.
2.) It would be much more productive to just go ahead and wire in 72pin SIMM sockets. Less connections, less of an unorthodox "ass-rig" and if the dram ever went bad, you'd be able to replace the SIMMs.
3.) You are talking about a VERY involved project. Not something worth writing up for others to easily attempt.
4.) Yes, any machine with at least a 68020 has a 32bit data bus and at least 4 gigs of physical address space. Its just a matter of designing the dram control/address circuits (or modding existing ones) to get the dram on the bus.
5.) I'd be willing to look at anything, and even attempt anything if price is no object, but unless theres already a standard simm socket there, the end result is not gonna be an easily repeatable "hack".

Ah, makes sense.  I don't know if anyone has ever managed to replace GVP SIMM sockets with standard ones?  You've given me something new to look into, thanks!