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Old 20 May 2019, 22:18   #1
kaluce
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sidecar ram, plus fast ram, chip ram behavior

Hi, I was looking at getting an upgrade to my A500, but I was curious how all of this would work out.

I have a standard A500 Rev.5 motherboard Amiga with KS1.3 for the record. I currently have a SupraDrive 500XP with 2mb fast ram, and the 512k trapdoor.

I was going to pick up something like the 2MB memory upgrade with Gary adapter: http://www.boobip.com/hardware/A500_2MB, but I was wondering how this would affect the sidecar ram already attached.

Would it be in addition to (meaning I get 4mb ram) or would it have the same addressable space, conflict out, or would one would win over the other? I like the sidecar, because it also has an 8gb SD card (emulating 4x2gb SCSI drives) so I'd rather not remove it if I can avoid it). Upgrading the ram is tricky, because it uses 1Mx4 20 pin DIP chips, which based on my research aren't produced from what I can tell, so I'd have to pillage something from an old ISA card, or try to find the chips in China or on Ebay. I'm not sure this is the best way to go about it.

Last edited by kaluce; 21 May 2019 at 17:32. Reason: deleted extra CRs
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Old 21 May 2019, 04:02   #2
lesta_smsc
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I have a Supradrive XP.

Why not upgrade the RAM inside Supradrive? It supports upto 8MB.

Also, I've still got the original scsi harddrive which when I last checked 1 month ago, it was still booting! How did you change to SD as this would ideal for WHDLoad set up.

Mine is running on A500+ so effectively 3MB RAM. But I have a 1MB trapdoor to make it 4MB!
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Old 21 May 2019, 07:38   #3
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Quote:
Originally Posted by kaluce View Post
Would it be in addition to (meaning I get 4mb ram) or would it have the same addressable space, conflict out, or would one would win over the other? I like the sidecar, because it also has an 8gb SD card (emulating 4x2gb SCSI drives) so I'd rather not remove it if I can avoid it).
No conflicts, but it will be slower to access than the RAM on your Supra. I recommend upgrading the Supra to 8MB as well. :-)
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Old 21 May 2019, 13:59   #4
jbilander
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Remember with rev 5 and the 2mb trapdoor ram you would need a 1mb Agnus in order to get 1mb chip ram (0.5mb from on board and 0.5mb from expansion), the other 1.5mb would then be mapped as slow ram if using the Gary adapter + jumper wire mod. I think this is how it would/should map without conflicts:

Address Range
000000-07FFFF First 512KB of chip RAM (from on board memory)
080000-0FFFFF Second 512KB of chip RAM (from trapdoor)

200000-5FFFFF Zorro-II space, First 4 MB Auto-config space / Fast RAM
600000-9FFFFF Zorro-II space, Second 4 MB Auto-config space / Fast RAM

C00000-C7FFFF 512KB Slow RAM (from trapdoor)
C80000-CFFFFF 512KB Slow RAM (from trapdoor)
D00000-D7FFFF 512KB Slow RAM (from trapdoor)

https://www.amigacoding.com/index.php/Amiga_memory_map

https://www.bigbookofamigahardware.c...t.aspx?id=1478
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Old 21 May 2019, 16:58   #5
kaluce
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Quote:
Originally Posted by lesta_smsc View Post
I have a Supradrive XP.

Why not upgrade the RAM inside Supradrive? It supports upto 8MB.

Also, I've still got the original scsi harddrive which when I last checked 1 month ago, it was still booting! How did you change to SD as this would ideal for WHDLoad set up.

Unless there's an adapter board I'm unaware of (please let there be, I really like the retro sidecar), the ram the SupraDrive uses isn't manufactured anymore (16x 1Mx4 DRAM, DIP20 package, 120ns or faster) currently I have 16 256kx4 DRAM chips loaded in it. I checked Aliexpress and Ebay for it, and the price I found for these is bordering on buying an accelerator card like the TerribleFire with the RAM onboard. If you are aware of something like an EDO ram or SMD adapter please let me know.



Regarding the drive, I used an SCSI2SD v4.1 which was around $30 ish on amigastore if I'm recalling correctly. It substantially lightens up the XP, draws FAR less power (which is good for the anemic A600 PSU), and allows you to configure an SD card in slices to report multiple drives to the SCSI controller in the 500 XP. The speed is noticeably faster than the stock ST325n 20mb drive as well. It also smells a lot better! For some reason that drive smells HORRIBLE.



There are newer versions of the SCSI2SD but I think that the additional speed (and cost) would be lost on the 500, I think we're really limited to floppy and the processor transfer speed at this point. I don't think the A500 supports DMA transfers.
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Old 21 May 2019, 17:21   #6
hooverphonique
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SMD-DIP adapters for DRAM chips comes up once and again here on the board - have a search
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Old 21 May 2019, 17:38   #7
jbilander
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Check post #11 on this thread: http://eab.abime.net/showthread.php?t=93679
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