5500/6500 RAM hack

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alk
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Joined: Dec 20 2003
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The 5500 and 6500 have only one drawback over their slower 5400 and 6400/6360 breathren - lower maximum RAM.

The 5500 and 6500 can only take 128MB of RAM, since they lack the 8MB on the motherboard of the 54/6400 (that give them a max of 136MB).

A cursory examination of the 5500/6500 motherboard shows four empty DRAM pads that ought to take the missing 8MB. All the hardware appears to be present that would allow a ceiling of 136MB _EXCEPT_ the DRAM modules.

Has anyone tried to solder in 4 DRAM chips from a scrap 54/6400? I've got a few spare boards and half a mind to do so, but I'm sorta busy with moving houses at the moment... If someone has some corroborating evidence, I might be made to spare some time and try it myself...

(No, I haven't bothered to download the dev notes just yet...)

Peace,
Drew

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Joined: May 29 2004
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i'd love to see it happen...

i have 2 old ppc 5500's that i have upgraded to the hilt and i've grown bored with them as projects... there's nothing left to do! if someone can get me a chip i'll just solder the darn thing on to one of them and give it a whirl.

MacTrash_1's picture
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55/6500 RAM hack

I'd like see it done also, but with larger chips. It seems like alot of work for only 8MB though.

Maybe larger chips......
Mmmmmm.....Chips......

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alk's picture
alk
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DRAM sizes...

It might be possible...

Alright, I have to go find the dev notes now. If the controller can access larger DRAM sizes, then 16 to 32 MB on the motherboard might be possible.

I'll let you know what I find out.

Peace,
Drew

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alk's picture
alk
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More info

Compare the 5400 and 5500 Dev Notes.
[ 5400 | 5500 ]

"Apple Computer" wrote:

The minimum bank size supported by the PSX IC is 4 MB and the largest is 32 MB; the largest DIMM supported is a two-bank DIMM holding 64 MB. Table 4-1 shows the single-bank DIMM configurations and sizes for a range of DRAM device sizes that are
supported on the Power Macintosh 5400 computer.

So the motherboard (one bank) can support up to 32MB. That's 4 chips of 4 M by 4 bits DRAM, 11 address rows, 11 address columns. Just gotta find those chips in the appropriate physical package...

Anyway, that would give the 5500/6500 (and 5400/6400 when applied to that board) an absolute max of 160MB of RAM.... unless we could figure out how to get a 2nd bank on the motherboard (to give 192MB max RAM).

Peace,
Drew

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