I know this isn't supported as the release notes for PIX 7.x & 8.x state that they require a minimum of 16MB Flash & 64MB DRAM. However the 7.0.x releases and the initial 8.x release are less than 8MB so would in theory fit in the 8MB flash. I know ADSM wouldn't fit in but does anyone know if this is possible? This is purely for a test environment as I would like to play around with PIX 7 and possibly 8 but don't want to shell out for an ASA or PIX 515.
I remember when PIX 7.0 was first released and Cisco said the 501 & 506 were not initially supported, but did indicate that a release would be available for these at some point. This has never happened though.