PowerBook 5300 FAQ

AlkSoft / Contents / Hardware / Logic Board

2.9) Logic Board

2.9.1) Can I upgrade my CPU?

In short, no. The 5300 is not processor upgradeable. However, PowerLogix developed a prototype PDS card CPU "upgrade," similar to the G3 processor cards that can be added to the PowerMac 6100. The card was based around a 130 MHz 603e and was going to carry the PowerBoost name, but it never came to market.

2.9.2) Can I use L2 cache?

No. Unfortunately, the exclusion of L2 cache on the 5300 is probably the single most crippling performance choice Apple made for this PowerBook. There is no facility for adding L2 cache from aftermarket suppliers, either.

2.9.3) Can I use a 2nd CPU?

No. But that's really only because none was ever manufactured. The PDS slot is perfectly capable of accepting a CPU or DOS card allowing all the same functionality that exists for the 6100 and many Quadras. However, no such card was ever manufactured. As mentioned above, PowerLogix developed a prototype CPU upgrade/accelerator but never brought it to market.

2.9.4) Can I use a PDS CPU upgrade card like in the 6100?

No. As mentioned above, this is really only because no such card were ever brought to market. PowerLogix did prototype a card called the PowerBoost that had a 130 MHz 603e and plugged into the PDS connector, but AFAIK it never left the prototype stage.

2.9.5) Can I overclock my CPU?

Yes. You can probably safely overclock the CPU by as much as 20%. There are two different approaches you can take, and both are detailed in the Appendix.

2.9.6) Can I use a upgrade my motherboard RAM or VRAM?

Possibly, depending on which logic board you have and how handy you are with a soldering iron. Most 5300s only have 8MB of RAM on the logic board, but they have space for 16MB. If you can find a set of spare chips matching the existing 8MB, you should be able to solder them to the logic board and upgrade your RAM in this fashion. This is a risky procedure, however, and the potential for destroying the RAM you are trying to install is high.

The same approach can be taken for VRAM. VRAM on the 5300 comes only in sizes 512kB. Adding a spare VRAM chip to a 512kB logic board _should_ upgrade you to 1MB total. I've attempted this upgrade myself, but as yet my success is inconclusive. My test machine is currently out of commission for other reasons...

2.9.7) Can I use the logic board from a 5300xx in my 5300xx?

Yes, and without restriction. The 5300 logic boards differ only in the amount of VRAM, RAM, and processor speed. There is nothing that would prevent a direct board-for-board swap.

2.9.8) What is this big chip marked <xxxx> on my logic board?

I've outlined what I know about the major chips on the logic board. The table below cross references the names of chips, their appearance, their position, and their function (if known). I've done my best to put together this information, but I don't promise that it is 100% correct. If you spot an error or an omission, please let me know.

Chip Name
Chip on the underside of the logic board titled "T-REX" with a large "LSI" logo.
This is a custom Apple application specific integrated circuit. It is the PCMCIA PC Card controller and provides all the standard ATA and other PC Card bus signals to the PC Card slots.
Chip labeled "IT&T ASCO 2300"
This is the 16-bit digital sound codec.


Labeled IBM PowerPC 603

- or -

This is the brain of the computer. It runs at either 100 MHz or 117 MHz and has 32 KB (16 KB data, 16 KB instructions) of L1 cache.

My RAM carries the Mitsubishi logo and a long Mitsubishi part number ending is "-7S" denoting that it is 70ns refresh rate.

There are up to 8 different ICs.

U28, U29, U31, U32, U8, U9, U11, U12
This is high speed storage for code and data when the computer is running.
My VRAM seems to be made by Texas Instruments and is labeled "TMS55165DGH."
U10, U30
This is high speed storage for video data when the computer is running.
Two different chips, one on the top and one on the bottom of the logic board. The top IC is a made by SEC and labeled 341S0145 HIGH. The bottom IC does not carry a manufacturer's logo, but it is labeled 341S0144 LOW.
U17 top,
U36 bottom
This IC contains the code that makes a Mac a Mac as well as code that controls how the PowerBook starts up.
PBX Memory Controller
Located immediately on the opposite side of the board from the CPU.
Labeled "©1994 APPLE
343S0147-02 B
The PBX Memory Controller controls access to the PowerBook's DRAM and ensures that RAM addresses appear contiguous to the operating system and software.
Baboon IC
Labled" ©1994 Apple
Controls all IDE devices (built-in hard drive and expansion bay devices)
Whitney IC
"LSI" chip labeled with "WHITNEY 3" on the top of the logic board.
The Whitney IC acts as a bridge between the system bus and the I/O bus (including peripheral ICs for devices such as the display, Singer IC, and IDE controller). The Whitney IC also incorporates several device controllers such as the SWIM floppy controller and VIA1 and VIA2 functions.
Combo IC
Has AMD logo, labeled "AM85C80-16VC"
Controls the serial bus and SCSI connections.
Power Manager IC
Labeled "SC428006PV 341S0187 PMU". Has a Motorola logo.
Controls sleep, startup, shutdown, and on/off modes, supports the Apple Desktop Bus, controls display birghtness, controls battery charging/charge level, and controls other power related functions.
Display Controller IC
Labeled "CHIPS T65225".
The Chips & Logic T65225 is a video controller and RAMDAC. It drives the built-in display.