If those 4MB show with your question card in place, 3MB it must be. Your PSRAM card is shown in the Apple Service Guide, Macintosh Computers Vol. 1 (1993) on p127. It is quite distinctive, in that the rows of six staggered chips follow the oblique upper edge of the card. The 1MB PSRAM card has only four staggered chips. Yours is evidently the later Portable, and you will find that the RAM expansion slot is keyed so that you do not try to insert an SRAM card (rows of eight chips, parallel to the bottom edge of the card), which is incompatible with your Mac.
You need have no concern about the apparent absence of a ROM SIMM. The portable would not have booted without the two ROM chips on the logic board (between the modem slot and the eight soldered-in PSRAM chips). The ROM slot is thus one of the several instances wherein Apple provided a slot 'in case ...' You are more likely to have trouble then if the ROM select jumper is not on its header (near the FDD connectors, and sometimes replaced by a DIP switch).
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You need have no concern about the apparent absence of a ROM SIMM. The portable would not have booted without the two ROM chips on the logic board (between the modem slot and the eight soldered-in PSRAM chips). The ROM slot is thus one of the several instances wherein Apple provided a slot 'in case ...' You are more likely to have trouble then if the ROM select jumper is not on its header (near the FDD connectors, and sometimes replaced by a DIP switch).
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