Need some help w/ Duo RAM limits...

[Dan K]

Craig W. wrote:
>I just got a Duo 2300c Parts machine on trade from a computer scrapper who 
>did not have a AC adapter to test it with....
>
>Anyway, it has 56k RAM (w/ a small board on top of the one that plugs into 
>the Motherboard). 
>
>While I like it, I have no intention of switching from my 280c (and I have 
>heard that the 2300c is not that much faster anyway). What I want to know 
>is: 
>CAN THE DUO 2300c's 48mb RAM BOARD WORK IN MY DUO 280c?

I'd suggest trying the 2300 with that ram module, it seems a shame to 
waste it in a 280c. I think a ram-maxed 2300 is quite an improvement over 
any 68K Duo, and the facility to use modern, fast ATA disks really tips 
the choice for me in favor of the 2300.

While I think the 48MB module may work OK, you'll have to try it to know 
for sure. Have you been able to boot the 'new' 2300 at all? What sort of 
problems (if any) does it have?

If you _really_really_ want to NOT use the 2300's LB and ram, I'd be 
pleased to trade you for it a 280/c appropriate 32MB module. <G>

BTW, I just replied with the answer below to a similar thread on the 
PowerBooks list, here it is in its entirety:

Re: Duo 2300c RAM

jutso at ripco.com wrote:
>Am I correct in assuming that the PowerBook Duo 2300c uses the same RAM
>cards as the previous Duos? I don't see anything in the Apple manuals &
>developer notes that suggest different.
>Since those RAM chips are 32-bit wide (I presume), & the 2300c has no L2
>cache, on top of that, that would lead to pretty gruesome performance. (I
>am vaguely considering upgrading a 270c, but am afraid that I will merely
>have exchanged the best of the '030 PBs (as such things go) for a lousy
>PPC PBook (as such things go).
A 280 LB upgrade will require a 280 chassis as well, the heatsink is 
different. My advice would be to leave the 270c as-is but keep yer eyes 
out for a maxed-ram 280/c, or better, a maxed-ram 2300c.

RAM cards for earlier Duos work in later Duos, but larger/later cards may 
not be able to be completely utilized in earlier Duos.

Some devnote quotes:
(Duos 210-250) "Third-party developers using 16-megabit DRAMs can develop 
expansion cards that
extend capacity to 24 megabytes."

(Duo 270C) "8 MB memory expansion card expands memory capacity up to 12 
MB; third-party
SIMM (single inline memory) card expands memory capacity up to 32 MB."

"In the PowerBook Duo 280 and 280c computers, the RAM expansion connector 
has an additional signal, RAS(7) on pin 24, that provides addressing for 
up to 36 MB of expansion RAM. A RAM expansion card for the newer machines 
also works in the older machines, except that any RAM over 32 MB is 
ignored."

"The RAM expansion card for the Macintosh PowerBook Duo 2300c computer is
compatible with the one used in earlier PowerBook Duo models. The 
computer accepts
up to 48 MB on a RAM expansion card."

-summary for your viewing pleasure-
model               baseram   max ram
Duos 210/230/250 -    4 MB     24 MB 
Duo 270C -            4 MB     32 MB
Duo 280 + 280c -      4 MB     36 MB
Duo 2300c -           8 MB     56 MB

As for 68K vs. PPC, speed depends on whether the app in question is 
native PPC or must be emulated. Well written native-PPC apps will almost 
always be faster than the 68K version was on a 68K Mac. Should one 
upgrade thus depends on what apps one intends to use.

A big problem with the 2300c however is PPC code is always larger than 
68K code, so if the 2300 in question doesn't have roughly double the ram 
of the previous 68K Duo it will surely disappoint. 48MB cards can be hard 
to find and rather pricey.

If there's one thing overwhelmingly in the 2300's favor, it's the ability 
to natively use newer/larger/faster ATA disks. A modern drive speeds 
everything up in a 2300, making a tremendous positive difference in 
usability.

Dan K
(now with a nearly-perfect Duo - 
2300/56/10g/OS9.1/mono-TFT-screen/NetDock)


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