Hey all!
Inspired by @Branchus 's latest video demoing Kero's new RAM boards, I wanted to return to and try to upgrade my PowerBook 540c's own RAM module.
RAM modules for the PowerBook 500 series are notoriously expensive now, and because the connector no longer exists, new boards cannot be fabbed. But assuming a board has the empty spots for them, it should be simple enough to add more chips of the same type already installed in order to upgrade it. This was actually discussed on 68kMLA at one point, and the experiments were successful.
My PowerBook's RAM module is a no-name 16MB card and looks like this:
As we can see, it has 8 DRAM chips (thus 2MB apiece), plus some I assume logic ICs. And luckily, it has 8 bare spots for additional chips, making this a perfect candidate for upgrading to 36MB.
The DRAMs are model number MCM517400BT-60. After doing some research with the data sheets, I discovered that they are Revision B's of the "Motorola 517400" (apparently a 'x4 2000 refresh cycle' CMOS DRAM, to be specific), fitted in a 0.300 inch TSOP II (thin small outline package, with the legs on the long sides of the component), and of course running at 60ns.
The original 517400, which I'll call Revision 'A', is part # "MCM517400T-60" (no revision letter), while the Revision C is "MCM517400CT-60". If we replace the 'T' with a 'J', they become SOJ packages (small outline package, J-leaded), which would be unsuitable, as outlined below.
Based on my research, the C version appears to be nearly identical to the B version, with the only differences appearing to be slightly better minimum stats on the 50ns variant, which obviously doesn't concern us since we're in need of the 60ns versions. However, the difference between the B/C and the original A version is significant, not least of which because the A version is packaged in a 0.400 inch TSOP, rather than 0.300. Although this number seems to refer to the thickness of the package, the 0.400 inch TSOP also happens to be a bit longer, meaning it wouldn't fit the available footprints, even if nothing else had changed.
Unfortunately I'm having trouble finding any RAM modules that have either the 517400BT-60 or the 517400CT-60 on them. Interestingly enough, although I don't need any new boards for this project, the 517400 series is listed as compatible with Kero's RAM project on his website.
If anyone has any suggestions, I would be very interested! Either the bare chips, or a sacrificial SIMM or DIMM module. The SOJ versions seem to be more common, which would be fine, except sadly, space is very tight inside the PowerBook 500.
Inspired by @Branchus 's latest video demoing Kero's new RAM boards, I wanted to return to and try to upgrade my PowerBook 540c's own RAM module.
RAM modules for the PowerBook 500 series are notoriously expensive now, and because the connector no longer exists, new boards cannot be fabbed. But assuming a board has the empty spots for them, it should be simple enough to add more chips of the same type already installed in order to upgrade it. This was actually discussed on 68kMLA at one point, and the experiments were successful.
My PowerBook's RAM module is a no-name 16MB card and looks like this:
As we can see, it has 8 DRAM chips (thus 2MB apiece), plus some I assume logic ICs. And luckily, it has 8 bare spots for additional chips, making this a perfect candidate for upgrading to 36MB.
The DRAMs are model number MCM517400BT-60. After doing some research with the data sheets, I discovered that they are Revision B's of the "Motorola 517400" (apparently a 'x4 2000 refresh cycle' CMOS DRAM, to be specific), fitted in a 0.300 inch TSOP II (thin small outline package, with the legs on the long sides of the component), and of course running at 60ns.
The original 517400, which I'll call Revision 'A', is part # "MCM517400T-60" (no revision letter), while the Revision C is "MCM517400CT-60". If we replace the 'T' with a 'J', they become SOJ packages (small outline package, J-leaded), which would be unsuitable, as outlined below.
Based on my research, the C version appears to be nearly identical to the B version, with the only differences appearing to be slightly better minimum stats on the 50ns variant, which obviously doesn't concern us since we're in need of the 60ns versions. However, the difference between the B/C and the original A version is significant, not least of which because the A version is packaged in a 0.400 inch TSOP, rather than 0.300. Although this number seems to refer to the thickness of the package, the 0.400 inch TSOP also happens to be a bit longer, meaning it wouldn't fit the available footprints, even if nothing else had changed.
Unfortunately I'm having trouble finding any RAM modules that have either the 517400BT-60 or the 517400CT-60 on them. Interestingly enough, although I don't need any new boards for this project, the 517400 series is listed as compatible with Kero's RAM project on his website.
If anyone has any suggestions, I would be very interested! Either the bare chips, or a sacrificial SIMM or DIMM module. The SOJ versions seem to be more common, which would be fine, except sadly, space is very tight inside the PowerBook 500.
