RT PC Memory Expansion
2MB Memory Expansion P/N 6298286, no FRU
Note the "2MB ECC Memory" in the upper left corner.
Lots of 41256-15 chips, 40 per side. There are also logic chips within the ranges 1-50 and 73-120, so don't get excited.
Note the lack of any jumpers. Fast Memory cards have a jumper to set speed.
HMS says P/N 629928
4MB Fast Memory Expansion PN 61X7005
Looks to be set up for interleaved memory. M1-40 and M41-M80 are 65X5506ESD. The center chips are all logic.
This card is only used with the RT PC Advanced Processor Board. (Oh?)
The HMS says to identify this card, look for the "4MB Enhanced ECC Memory" printed on the option.
J3 HMS only shows this jumper in the "Fast" position. No explanation.
"When using 'Enhanced ECC memory' boards, make sure that the jumper
on the memory cards is in the 'fast' position. The undocumented jumper
allows the newer cards to work with the older processors by moving it to
the 'slow' position.
8MB Fast Memory Expansion P/N 60X5777, no FRU
Same layout as the 4MB Fast Memory Expansion, but at least on this one, there is a sticker saying "8MB Enhanced ECC Memory" top center.
M1-M80 are 6470780ESD.
HMS says P/N 61X7009
J3 HMS only shows this jumper in
the "Fast" position. No explanation.
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