I use PCMCIA to CF and PCMCIA Flash Memory cards (SanDisk has a few >1GB Flash Memory Cards, seen them on Ebay), on System 7.5/7.6 on my PB 190 & 5300 and System 7.6 and OS 8 on my 1400s and Wallstreet G3. All of them are bootable and useable. It was the first of my SSD Experiments long ago and now I have them as system Back Ups in case of HD Failure. No drivers are needed for PCMCIA with Macs that I seen so far. (See note below)
Personally I never seen a SD to PCMCIA adapter, and like TechKnight said, there is a difference between PCMCIA and CardBus cards though they might slide into the slot. I also seen but never tried, and it might be better for you, a SD to CF Adapter, which you can use in a PCMCIA and it should be bootable. Keyword is "Should Be."
This ebay link is to show you what a SD to CF Adapter looks like, it is not that I am recommending the seller.
http://www.ebay.com/itm/New-Arrival-SDXC-SDHC-WIFI-SD-to-Type-I-Compact-Flash-Card-Adapter-CF-ADAPTER-/261749536654?pt=LH_DefaultDomain_0&hash=item3cf17cf78e
Note: Mind you, I am talking about 68K and PPC Mac powerbooks. I have yet been able to get them to boot up a PC Laptop even though I read the instructions, put in drivers, formatted cards and etc. If I can get a PC laptop boot from PCMCIA, I'd be dancing a jig, I swear! But as far as Macs go, you can boot from PCMCIA memory cards and PCMCIA/CF memory cards.
Personally I never seen a SD to PCMCIA adapter, and like TechKnight said, there is a difference between PCMCIA and CardBus cards though they might slide into the slot. I also seen but never tried, and it might be better for you, a SD to CF Adapter, which you can use in a PCMCIA and it should be bootable. Keyword is "Should Be."
This ebay link is to show you what a SD to CF Adapter looks like, it is not that I am recommending the seller.
http://www.ebay.com/itm/New-Arrival-SDXC-SDHC-WIFI-SD-to-Type-I-Compact-Flash-Card-Adapter-CF-ADAPTER-/261749536654?pt=LH_DefaultDomain_0&hash=item3cf17cf78e
Note: Mind you, I am talking about 68K and PPC Mac powerbooks. I have yet been able to get them to boot up a PC Laptop even though I read the instructions, put in drivers, formatted cards and etc. If I can get a PC laptop boot from PCMCIA, I'd be dancing a jig, I swear! But as far as Macs go, you can boot from PCMCIA memory cards and PCMCIA/CF memory cards.