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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: on March 06, 2007, 06:12:55 AM
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After a bit of investigation, the cheapest source of RAM for my 3000s is ZIPs from Software Hut at 4$ each.
For 16MB that's 128$. That smells outrageously expensive.
One of the reasons why it is not possible to use just any type of RAM in a 3000 is because of the memory refresh system impersonated by RAMSEY.
However, the 3000 and the 4000 have one major advantage, they support Zorro III which allows for 32 bit communication and a very large addressing range. I remember seeing Zorro III expansion cards for the 3000 that could carry up to 64MB of RAM back in the early 90s.
The reason why most RAM expansion boards are expensive is because they require refreshing systems. But today, there are very cheap memory chips that require no refreshing. Their just too slow for most ordinary PCs but slow being a relative thing, they are fast enough for just about any 68k based Amigas with 70ns response time.
Nicer even, they don't use multiplexed address lines.
I found this chip on Digikey which can be purchased by the unit for 11$ each: http://download.micron.com/pdf/datasheets/psram/BurstCellularRAM1.5_128Mb.pdf
This chip has 16 data lines and contains 128Mb of data therefore two of them fullfills the 32bit data bus requirement for 68030, 040 and 060 processors and give you 32MBytes for 22$. It requires absolutely no refreshing but it has a drawback. It operates at low voltage... therefore it would require a couple of 1$ voltage buffers to be usable with Amiga which mostly all operate at 5V. Biiiiiig deal!
Am I just plain stupid to believe that a very cheap board could use these chips to offer large amounts of RAM at a very low cost to Amiga users?
Or is there some serious technical hurdle that prevents these chips from working fine with Amiga computers?
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I have been buying RAM for $45.00 for 512MB anytime I feel like it since November 2004. These are not bulk purchases. I just walk into the local computer store and buy 1 whenever I need one. Why don't you make a board to use it?
I can't believe you are trying to charge people $22.00 for only 32 MB of ram. That smells outrageously expensive.
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ChaosLord wrote:
I have been buying RAM for $45.00 for 512MB anytime I feel like it since November 2004. These are not bulk purchases. I just walk into the local computer store and buy 1 whenever I need one. Why don't you make a board to use it?
I can't believe you are trying to charge people $22.00 for only 32 MB of ram. That smells outrageously expensive.
Well, I wish you real good luck getting the corner PC store's DDR SDRAM to work on a 68k based Amiga... The reason why such incredibly complex memory systems cost so little (the dram access, refresh and control systems of most modern PCs) is simply because they are sold by the millions.
If there was a board that would allow DDR SDRAM (and SDRAM stands for SYNCHRONEOUS DYNAMIC RAM, not static) to be used on an Amiga it would probably cost no less than 100'000$ to develop. When you can spread this cost across millions of units you know will sell, that's not a problem. The Amiga community doesn't have such a large user base to justify that.
By contrast, static RAM requires no refreshing, no multiplexing of the address lines and consumes incredibly little power. Static RAM is very popular in non-PC digital systems where simplicity of the design is important.
Static RAM chips require incredibly less technical expertise to use because technically speaking, they can be connected directly to the processor's bus without any special chips surrounding them, unlike any other form of dynamic RAM.
It think it is fair to assume it could be possible to develop a working prototype of a ZII/ZIII RAM card that uses these chips for around 1000$.
I'm looking for a way to offer more RAM to all Amiga 1200/2000/3000/4000, not a way to dream about unreacheable things.
Still, if you find that expensive, tell yourself that back in 1992, DRAM was 50$ per MB. Today, ZIPs are 8$ per MB but these static RAM chips are 69 cents per MB. A considerable drop. They would also consume less power than a single one of the traditional ZIP chips.
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Well said eslapion. This sounds like a great project. Good luck with it!
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moto
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If you want it cheap: read this (http://www.amiga.org/forums/showthread.php?t=27574).
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Zac67 wrote:
If you want it cheap: read this (http://www.amiga.org/forums/showthread.php?t=27574).
Yeah, the SIP, or should I say the "Patience and meticulous" solution.
That implies you still use the onboard system of your Amiga (3000 in that particular case) to refresh and control access to your memory. Well, in the case of the 3000, this means you will always be limited to 16MB of fast RAM.
How many address lines exactly are there on the Z3 bus? I think that's 32 and therefore your fast RAM limit is more like 4GB (but that would probably be 2GB cuz you always have to have the custom chips and the chip RAM somewhere).
But still, at 22$ per slice of 32MB, this means you could get 64MB for 44$ or 128MB for 88$.
Also, static RAM standards change much less often than PC based dynamic RAMs. There also very popular with other systems such as satellite TV receivers and DVD players/recorders because of the low power requirements and easy design.
Any good electrical engineer wants to help?
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I'm guessing that there is more demand for a Zorro 3 RAM card than Z2 or A1200. Since Z2 cards are relatively cheap and common, and the A1200 expansion port is often used for an accelerator (and both have limitted address space). Take a look here:
http://www.thule.no/haynie/zorroiii/docs/zorro3.pdf
I bet you could avoid the autoconfig stuff and put the memory at a fixed address (or have a choice of addresses by jumper setting). Then run a utility in startup-sequence to add the memory.
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If you're planning to build a Zorro RAM expansion, why not build it to accept DDR/SDR? Is that possible?
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moto
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One of the reasons why it is not possible to use just any type of RAM in a 3000 is because of the memory refresh system impersonated by RAMSEY
Ermm, 30 pin and 72 pin SIMMs would run just fime from the Ramsey timing.. ok you couldnt stick SD-Ram in but a 72 pin adaptor would be much easier to do. (And has been done before, including free designs available from Aminet today)
I found this chip on Digikey which can be purchased by the unit for 11$ each: http://download.micron.com/pdf/datasheets/psram/BurstCellularRAM1.5_128Mb.pdf This chip has 16 data lines and contains 128Mb of data therefore two of them fullfills the 32bit data bus requirement for 68030, 040 and 060 processors and give you 32MBytes for 22$. I
Ermm its a 16 bit chip that gives you eight megabyte of memory, sticking two side by side (Connected to the same address pins) would give you 16, an address decoder would be needed for 32. (and four memory chips)
I can't believe you are trying to charge people $22.00 for only 32 MB of ram. That smells outrageously expensive. Well, I wish you real good luck getting the corner PC store's DDR SDRAM to work on a 68k based Amiga...
I think he was commenting on your use of "outrageously expensive" when talking about the ZIP ram, it isnt expensive (Your not ment to use it for adding loads of ram, at 1meg its cheap) its just there are cheaper options, you give the BGA memory chip, he gives you PC DDR Ram.
How many address lines exactly are there on the Z3 bus? I think that's 32 and therefore your fast RAM limit is more like 4GB (but that would probably be 2GB cuz you always have to have the custom chips and the chip RAM somewhere).
Actually 31, it doesnt support 8 bit reads, it reads 16bit at a time minimum, regardless wether or not only 8 bits are in use. but thats a nothing reply, yes the CPU is 32 bit and it can address 4GB total.
Take a look here: http://www.thule.no/haynie/zorroiii/docs/zorro3.pdf I bet you could avoid the autoconfig stuff and put the memory at a fixed address (or have a choice of addresses by jumper setting). Then run a utility in startup-sequence to add the memory.
Actually that card uses ZIP ram too, although adding 72 pin SIMM slots would be a piece of cake. Its a good design and if you wanted to make a memory card that is the design you should use. Upping the maximum RAM is just a matter of adding another 74257 (or 258) to get the extra address lines as the Miggy will detect how much ram is on the card.
Its also a lot easier than your BGA memory chip which would still require logic chips as CRE and ADV would have to be generated.
If you're planning to build a Zorro RAM expansion, why not build it to accept DDR/SDR? Is that possible?
It is, Xilinx have a design you can download, as do opencores I think.
All someone has to do is try... oh but they will have to add autoconfig and make sure the output bus is 68K compatiable. Also SD and DDR ram are clocked memory, the Zorro bus is asyncronous memory, its not great to mix the two busses... that said you look at 90% of Z3 boards and they are syncronous.
Get designing people. :)
eslapion: To sum up, designing a 72pin SIMM board would be much easier for a hobbiest to do than to start playing around with high density BGA chips.
32Meg 72 pin Simms are still available new, cheap, from most PC suppliers. Eclipse computers here in the UK sell them for £5.82 each. Make a Fastlane type board with 16 72 pin slots and you get half a gig for less than £100
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Given Oli_hd's explanation, would it be reasonable to ask Individual Computers to build such boards? Jens and his crew coped with autoconfig and such things before.
If it's easy enough for them, only demand would be an issue.
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yup, get a list of people who would be interested, hand it to Jens and see.
I dont know what Jens is working on now, it may be an ideal time to ask.
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Lets start a list of potential buyers somewhere then. Any idea what a DKB 3128 goes for these days if you can find one:-D?
-Jeff
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Any idea what a DKB 3128 goes for these days if you can find one?
About $150 USD, more for a Fastlane (Specially if the guy words it like it "may" have the 256Meg upgrade)
Aim at £100 and it would be Jens most expensive card I think, so thats a good target.
512Meg Z3 memory card please.
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My interest is certainly piqued by the thought of being able to use common ram SIMMs in an A3000 card. I have an A3000 as my backup Amiga.
However, my main Amiga is an A2000, am I correct in stating that the A2000 does not have the same capabilities as the A3000 for Zorro slot RAM expansion? i.e. it can only accept a max of 8MB on the Zorro slots, or has trouble DMAing to a processor in the accelerator slot? Even if it were possible it would be slow 16-bit RAM, right?
Basically, wanting a 128MB RAM card on a Zorro II card for the A2000 is just an impossible dream, right?
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Speaking of Xilinx, there are several FPGA dev boards out there that have DDR ram already installed. Up to 32MB ore more. They have free cores to interface the DDR ram as if it were static ram. Why not simply use one of those boards on a carrier designed to fit the Zorro slot?
A board like This one from XESS (http://www.xess.com/prod034.php3) is only 89 bucks... and it has ps/2 and VGA ports which open up other fun possibilities. ;-)
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Basically, wanting a 128MB RAM card on a Zorro II card for the A2000 is just an impossible dream, right?
Correct, no way around the 8meg Zorro limit.
However I assume as your using an A2000 over an A3000 you have a CPU upgrade in the A2K, that could take a suitable card.
For example my A2630 has the full 32bit address and data lines brought out to two connectors (Which is why there is the 2632, a memory card for the A2630 that plugs into said plugs)
Also a new A2000 CPU card could be made with as much ram (less than 4gig - 16meg) as wanted.
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Why not simply use one of those boards on a carrier designed to fit the Zorro slot?
Do you like the look of the XSurf?
carrier boards suck eggs.
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DamageX wrote:
I bet you could avoid the autoconfig stuff and put the memory at a fixed address (or have a choice of addresses by jumper setting). Then run a utility in startup-sequence to add the memory.
Quoting The Master and writing this in one and the same post - you must be out of your mind... :roll:
The Autoconfig logic is very easy to do.
@all
Actually I doubt if there's really a large demand for Z3 RAM boards: they're slower than onboard RAM (which isn't fast either) and paired with a CPU board will be a real pain. A far superior solution is to add the RAM on an accelerator board - which is why nearly all of them come (came) with RAM slots.
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Oli_hd wrote:
Ermm, 30 pin and 72 pin SIMMs would run just fime from the Ramsey timing.. ok you couldnt stick SD-Ram in but a 72 pin adaptor would be much easier to do. (And has been done before, including free designs available from Aminet today)
I suspected something like that. Would you have a few links to these free designs?
Actually that card uses ZIP ram too, although adding 72 pin SIMM slots would be a piece of cake. Its a good design and if you wanted to make a memory card that is the design you should use. Upping the maximum RAM is just a matter of adding another 74257 (or 258) to get the extra address lines as the Miggy will detect how much ram is on the card.
What card exactly are you referring to?
Its also a lot easier than your BGA memory chip which would still require logic chips as CRE and ADV would have to be generated.
Now thats the kind of technical hurdle I wanted people to tell me about. What exactly are CRE and ADV ?
eslapion: To sum up, designing a 72pin SIMM board would be much easier for a hobbiest to do than to start playing around with high density BGA chips.
Electrically, static memory chips seemed much easier to deal with than DRAM. However, soldering VFBGA (that's VERY FINE ball grid array...) chips would certainly be a true pain in the neck...
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Oli_hd wrote:
Do you like the look of the XSurf?
carrier boards suck eggs.
Actually, I don't give a rodent's rump what it looks like, so long as it works. ;-) My thinking was this was a personal hack, not a commercial product. So it would be easier to produce a carrier board that fit the Zorro slot and could be hand soldered, rather than try to deal with those SMT chips.
-Jim
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JimS wrote:
Actually, I don't give a rodent's rump what it looks like, so long as it works. ;-) My thinking was this was a personal hack, not a commercial product. So it would be easier to produce a carrier board that fit the Zorro slot and could be hand soldered, rather than try to deal with those SMT chips.
-Jim
Well, it "could" have become a commercial product...
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eslapion wrote:
Well, it "could" have become a commercial product...
It still could, if someone thinks there's a big enough market to make it worthwhile.
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Quoting The Master and writing this in one and the same post - you must be out of your mind...
The Autoconfig logic is very easy to do.
LOL, well if we're already considering pseudo-SRAM instead of SIMMs or DIMMs then I say leave no corner uncut.
Z3 RAM boards: they're slower than onboard RAM
If I'm not mistaken (no, I did not read through the whole Z3 spec) a Z3 board COULD be as fast or faster when taking advantage of faster memory. A3k/A4k onboard memory is 80 or 100ns right?
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Well, in theory a Z3 card could be faster than A3k/4k onboard RAM - but not with existing chipsets. A3k/4k can't drive the bus as fast as they can access Ramsey mem.
Onboard RAM must be 80ns or faster, yes.
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z3 access is multiplexed address/data cycles. that puts a layer between the cpu and bus controlled by the chipset. dma burst modes are similar but different than 030 and quite a bit different than 040 burst.
i dont think it could be as fast.
a memory card that clipped on top of surface mount 030 or under pga 030 or 040 would be better. there is better info on the interface and it would concevably be usable on accel boards as well.
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KThunder wrote:
z3 access is multiplexed address/data cycles. that puts a layer between the cpu and bus controlled by the chipset. dma burst modes are similar but different than 030 and quite a bit different than 040 burst.
i dont think it could be as fast.
a memory card that clipped on top of surface mount 030 or under pga 030 or 040 would be better. there is better info on the interface and it would concevably be usable on accel boards as well.
Well, considering we're dealing with ultra small chips, it could be possible to make some card that gets sandwiched between a 680(3 or 4 or 6)0 and its socket.
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Re: ZIP to SIMM Adaptor
I suspected something like that. Would you have a few links to these free designs?
http://aminet.net/hard/hack/PS2_adapter.lha (http://aminet.net/hard/hack/PS2_adapter.lha) is the A3000 adaptor with image of the PCB you need to make.
Amifast card (http://amiga.resource.cx/exp/amifast)
was a card made by Provtech but chances are you will see more of Kato's simmfonie (http://amiga.resource.cx/exp/simmfonie) card.
Re: Z3 memory card:
What card exactly are you referring to?
The Commodore Bigram, it was made as a Z3 reference design back when the A3000 was launched to show CAT's developers how to design Z3 cards. The design was given away free and is still available from the Dave Haynie archive (http://www.thule.no/haynie/zorroiii/bigram/docs/bigram1.pdf)
More information on the card, including a picture, is available at amiga-hardware.com (http://amiga-hardware.com/showhardware.cgi?HARDID=975)
Now thats the kind of technical hurdle I wanted people to tell me about. What exactly are CRE and ADV ?
They are specific to that chip I think, unlike normal ram you have to tell this when your not using it or if your running a burst cycle, these extra signals combined with the normal signals are used for that. Details are in the PDF of that memory chip you were talking about.
Normal Dram (And SDRam) havce RAS and CAS and thats it (SDRam add chip select, or BE, but they are just address lines)
Electrically, static memory chips seemed much easier to deal with than DRAM. However, soldering VFBGA (that's VERY FINE ball grid array...) chips would certainly be a true pain in the neck...
Well SRAM is, this ram you linked to isnt. SRAM is treated just like a ROM and is dead easy, everything is sorted inside the chip. Down side is SRAM is expensive and the memory you linked to would need extra chips to control it, just like DRAM does (Although not the same chip as the lines do different things)
DRAM is simple, you just have to split the address bus and load it into the ram half at a time (using RAS and CAS to tell the RAM what half is on the address bus at that time) and refresh the ram every so often so the contents are not lost.
Have a look at some of the Zorro 2 dram cards on amiga.resource.cx, there are some simple designs.
Zorro 3 just adds address and data latches and adds more memory.
I don't give a rodent's rump what it looks like, so long as it works.
:-? I want the Delfina lite, not because its the best card but because its sexy. :-D
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Eslapion about DDR:
...Amiga it would probably cost no less than 100'000$ to develop. When you can spread this cost across millions of units you know will sell, that's not a problem. The Amiga community doesn't have such a large user base to justify that.
$100000 for development sounds a bit pricey, i don't buy that. Maybe some $1000s is more realistic. How about SDR-SDRAM, which is a bit more simple to interface. And a bit more expensive, unless bought second hand.
It wouldn't need many parts: One PLD, one (or more) SDRAM-socket, a printed circuit board and some capacitors, resistors, and a voltage regulator or two.
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mrmkl wrote:
$100000 for development sounds a bit pricey, i don't buy that. Maybe some $1000s is more realistic. How about SDR-SDRAM, which is a bit more simple to interface. And a bit more expensive, unless bought second hand.
It wouldn't need many parts: One PLD, one (or more) SDRAM-socket, a printed circuit board and some capacitors, resistors, and a voltage regulator or two.
The problem with both SDR SDRAM and DDR SDRAM DIMMs is that they were designed to be accessed with 64 bit data busses.
Now, that's fine with processors from the original Pentium I all the way up to the fastest core 2 duo which have 64 data lines (in Pentium I systems, 10 years ago, 32 bit 72 pin SIMMs had to be installed in pairs). However, it is a major problem with 680X0 systems which cannot access more than 32 data lines at a time.
Here is the kind of problem that it causes. Let's say you want to write into the lower half one of the 64bit cells of a DIMM with a 68040. You first have to read the content of the cell into a buffer so you know what was first in there. Then replace the content of the lower portion of the buffer with what the processor wanted to write in there, then write this back to the cell.
As you can see, this is quite complicated.
One of the reasons I originally suggested PSRAM, is that, by pairing 2 of these 16 bit chips together, you get exactly 32 data lines. So theoretically, you could attach chips like that without ANY logic devices at all directly to the bus of a 68030, 68040, 68060 or even an intel 486 processor.
No refresh, no multiplexing needed and no logic to compensate for inadequate bus width. Perhaps a few simple 74XX chips for address decoding.
The only reason why some MINIMAL logic would be required with PSRAM, as far as I know, is the autoconfig procedure.
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I've also pondered on the 'SDRAM DIMMs are 64 bit wide' problem a bit.
Given the low price of the RAM, you can just use one half of it and forget about the rest (either double data or ignore it altogether). If you want large amounts of RAM, it's the easiest and cheapest solution - you could even use slightly defective modules. ;-)
Aiming at the 16 to 128 MB size range, it's surely easier and cheaper to use old PS/2s, they're free.
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While the slot is 64 bit the DIMM memory modules are often made up of 8 or 16 bit IC's which are controlled by the DQMB lines on the SD-Ram connector.
There are 8 DQMB lines, enough for 8bit control of the 64bit bus, technically you could interface an 8bit CPU to the SD-Ram, the down side is like I said, some are chained as 16bit, some I think even 32 but Im 90% sure there are no 64bit only DIMM's.
Some good reading on SD-Ram DIMM layouts is available from this document:
PC133 SDRAM Registered DIMM Design Specification Revision 1.1 (http://www.simmtester.com/PAGE/memory/techdata_pc133rev1_1.pdf)
And for a more techincal doc on how SD-Ram works you need to read this:
PC SDRAM Specification Revision 1.7 (http://turhalmyo.gop.edu.tr/ogr/ebu/donanim/sdram133.pdf)
The only reason why some MINIMAL logic would be required with PSRAM, as far as I know, is the autoconfig procedure.
Your memory speed would such, you will need to implement a burst system.. which is Z3 specific (Well its based on the 030 bus burst system but you know...) and without that its one read or write per bus cycle vs four using burst.
Also Z3 has a multiplexed bus, the data and address busses are the same thing, it just has an address phase and data phase, your going to need the full array of bus buffers and latches to decode that.
Its still going to be a big job... your best bet would be to get a nice big CPLD or FPGA and connect the Zorro bus to one end and the SD-Ram slot to the other then work everything out in software.
Final edit: As a little example Eclipse computers (A cheap ass UK computer company) is selling a 512Meg SD-Ram DIMM (http://www.eclipsecomputers.com/product.aspx?code=MED-5123M) for £30 and they list it as a 16 chip module with each chip having 32meg and an 8 bit bus. Which technically gives a 128bit bus, so every two chips must be coupled to the same DQMB line, giving a 16bit CPU bus, taa dahh.
So who's making a Z2 version? (I joke, although you could have a rather nifty 8meg SD-Ram upgrade card working on an A2000)
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Anybody know of a supplier for some of these psrams? low density srams are stupid expensive and can be a pain to source.
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koaftder wrote:
Anybody know of a supplier for some of these psrams? low density srams are stupid expensive and can be a pain to source.
As stated earlier, Digikey has these chips. They sell by the unit or by the thousands.