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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: curtis on May 11, 2018, 10:06:43 PM
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So I've got this in my 2000 with 8MB RAM installed and was wondering if I could install 4MB simms for a total of 32MB RAM. Everything I've read said it's not possible. That only 8MB is available on this due to the 68030-25 cpu.
Is that right? It really doesn't make sense that the speed of the cpu limits the amount of RAM.
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BBOAH says that board supports a maximum of 8MB:
http://www.bigbookofamigahardware.com/bboah/product.aspx?id=1635
Also looks like it uses the proprietary GVP SIMM's.
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check here also: http://amiga.resource.cx/exp/a3001mk2
apparently the 16-25mhz boards take 8mb on the ram board, and 50mhz could take 20mb.
Some gvp board could use the a2632 with 112MB ram, but i think that old 3001 will not,but check into it,i could be wrong. Jens made a new run of A2632's a while back.
some later gforce boards(040?) could take 64MB of special 16MB gvp simms($$$).
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And everybody restated exactly what I already knew.
I want to know WHY?
Why is the 25MHz board restricted to 8MB.
Why can it not use the higher RAM amounts?
Doesn't make sense to me.
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I want to know WHY?
What do you think? Because the 25Mhz version is the entry-level board, and GVP wanted to create some incentives for users to buy the more expensive variants. The glue logic on the board is different, and 8MB is the limit the board can allocate in the autoconfig area. 32-bit access requires additional logic, or at least different programming of the board logic.
From a product definition point of view, this makes perfect sense to me.
Why is the 25MHz board restricted to 8MB.
If you don't like this answer... well, "Because they decided so". That's it. Too late to complain about.
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Myriad technical or cost-cutting measures. Why can't my 68060 run at 600MHz? Why can't I add 100MB of RAM to a stock A500, etc. Like the old beer commercial said, "why ask why?" :lol:
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Myriad technical or cost-cutting measures. Why can't my 68060 run at 600MHz? Why can't I add 100MB of RAM to a stock A500, etc. Like the old beer commercial said, "why ask why?" :lol:
How exactly does a posi-trac rear end on a Plymouth work?
No one knows! It just does.
Sorry..... had to say it! :roflmao:
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I had this http://amiga.resource.cx/exp/a3001, with 8mb daughter board.
Memory is mapped to Zorro II space, so no RTG with more than 4mb ram.
It uses rare nibble mode sims, (what ever it means?) so it seems that some people has managed to get quite much money when selling them.
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THAT'S what I wanted to know!
Thanks Thomas.
Curtsi
What do you think? Because the 25Mhz version is the entry-level board, and GVP wanted to create some incentives for users to buy the more expensive variants. The glue logic on the board is different, and 8MB is the limit the board can allocate in the autoconfig area. 32-bit access requires additional logic, or at least different programming of the board logic.
From a product definition point of view, this makes perfect sense to me.
If you don't like this answer... well, "Because they decided so". That's it. Too late to complain about.
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Original A3001 had 4 MB and 8MB of Nibble mode SIMMs, placed via AutoConfig, into the 8MB space. ~1988-1989 IIRC. Supported DMA from Zorro II. I think it beat the A2630 out (not the A2620), and was the first to do this. Ronin, CSA, and any others of the early accelerator group either mapped it high, or didn't support DMA in the AutoConfig space, if they autoConfig'd it in the first place (AddMem!). It was called the A3001 because it was better (faster) than the A3000 that was yet to appear on the market. It pissed C= off a tad, at the time, yes.
Nibble-mode memory directly supports 68030 CPU burst mode, which sends 4 bits instead of one per memory access, thereby populating the cache more efficiently for sequential instruction and data accesses. you needed 4 modules as each 30-pin SIMM was 8-bits wide. You pay a small penalty if all you needed was 1 32-bit longword.
If you had a sequential need for data, and memory clock penalty was 3 for each 32-bit longword, you got 4 longwords in 12 clocks. In burst, it takes 6, assuming 3-1-1-1. Varies based on memory speed, and the clock of the CPU. I don't recall the settings on the memory boards, but 3-1-1-1 and 4-1-1-1 seem like they applied - distant memories. 50Mhz may have been 5-2-2-2 or 6-2-2-2, but remember this is 50Mhz clocks, not 25/28 or 33Mhz.
RAM32 memory card and the SIMM32's came out to replace the nibble-mode SIMMs and uses them in groups of 4 to get the same kind of 'burst' from memory that only sends 1-bit (x32). At the time, 32-bit SIMM standards were not established. GVP made their own, and the design was for 1, 4, and 16MB modules, but the original boards only supported the classic 8MB AutoConfig. Same with the 33Mhz. Note the SIMM32 memory is not 80ns or 70ns like the nibble-mode memory, but 60ns, so boards' memory logic are tuned to that speed, which improved at some speeds.
The RAM32 board is identical between speed variants, but the PALs used (and jumpers) select different AutoConfig amounts, clock timing, and addresses the memory is found at. Memory mapped high is detected by the v3.x driver ROM and mapped into the free memory list very early on.
Later, the 50Mhz top of the line board got 4/8 Autoconfig with 1MB SIMMs, or the same 4MB with 1MB modules + 4/8/12/16 mapped high with 4MB modules, and the memory clocking was adjusted for 50Mhz. A later revision got 4/8MB AutoConfig with only 4MB modules, and 4/8/12/16/20/24 mapped high, or optionally all modules mapped high for 32MB.
The low end 25/28/33Mhz A3001 sandwich boards were replaced with the Combo 22/33Mhz SMC series, and then all were replaced with the G-Force (PGA CPU) 68030 line (25MhzEC/40MhzEC/50MhzFull).
The G-Force 68040 was the first to use the 16MB variants of the module, but supported the 4MB version.
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@thebajaguy Very good explanation! Sorry for resuming this very old thread but is of my interest… I have A3001, my question is: the pal on ram32 is really different from 33 and 50mhz version or are identical and change only the jumpers setup? My problem is the ram32 work good at 33 (and 40) mhz but no way to go it at 50mhz and map high the memory :-(
The cpu card work good at 50mhz, ram32 not… (tried some jumpers configuration, some simm’s ecc…)
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It can be said that a 50MHz-configured board will run at 33MHz or slower, but it's memory-access timing is not optimal for that clock.
The programmable logic in the PALs, combined with the jumpers (which control clock and bus-signal sources, some being negated, etc, if I am recalling correctly) produce the optimum timing for the board speed it was set up for. Trying to go faster (clock) on a slower-configured memory board won't work.
Although some logic is common between boards for a few things (the memory-detect and/or AutoConfig details), there were no 'generic' part sets that applied to the address-generation/data-access logic. It was timed to a clock speed for best performance.
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Ok! But the question is: my ram32 board is damaged or it born to run at 33mhz and can’t go at 50mhz?
Sorry for my poor English :-)
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@thebajaguy
Can be the rom?
At 50mhz the 1mb simm always do a defective on boot diagnostics, probably the a3001 at 50mhz not support 1mb simm, and can’t map memory on zorro2 space. With 4mb simm mapped high, the memory board (and the memory) is not visible, I can assume the card is not mapped on zorro2 space and based on your explanation the rom enable the ram and map it high… but this not happens! My Rom is 3.3 and insert it, or removing, nothing change.
The two roms u24 u25 are needed only for unix? In my board are missing.