A good place to start. FP4's will probably have PROM 4.1, or perhaps 4.1.2. You can manage them from a DIRECTLY connected LocalTalk or EtherTalk (Phase I) connected Mac running FastPath Manager (FPM). [This is also true for FP2's or FP3's which were upgraded to 2U's or 3U's] FPM uses "KLAP" -- a packet with "LAP" type 0x4b (the letter 'K'), which cannot be routed. An FP4 could be upgraded in two ways; Just a new PROM (5.1), or a new PROM, and a 256K SRAM memory board (for a total of 512K), which came with a new case, and a fan. A box with PROM v5.1 can be managed with FPM, or via Shiva Net Manager (SNM). SNM only speaks KLAP over DDP (or was that ATP). DDP is the regular AppleTalk network layer, so you can speak to boxes via intervening AppleTalk routers. ATP is the transaction protocol, layered on DDP. The CPU clock on the FP4 68000, was, I believe 8MHz. FP5's started with PROM v5.0 [FP5's use their PROM only to load the "VROM" -- a protected memory version of the PROM code]. FP5's came with 512K standard, and could be built with (or, I suppose upgraded to) up to 1MB, and the CPU clock was, I believe 10MHz. The FP4 is perhaps, more flexible in the hands of a hacker, since you could take direct control of the SCC, and do async or perhaps sync serial. On the FP5, the SCC is part of the I/O Processor (a Zilog Z181), and I never did an API to load code into the IOP. All versions of the FastPath PROM provide a vector of routines which the download can call. In PROM v4 and up, this includes access to the Ethernet driver, which is how we got away with replacing the iNTEL Ethernet controller from the FP1/2/3/4 with the Fujitsu EtherStar -- the download (K-STAR) doesn't care what the hardware is (direct SCC and i82586 on the FP4, or IOP and EtherStar in the FP5). On powerup, the PROM spends 20(?) seconds flashing LEDs, then starts the download, or the built in PROM GW (removed in v5), which is a simple Phase1/LocalTalk router (with no IP capabilities). Its's best to pause or reset the box before it gets rolling, in case it's misconfigured or otherwise frotzed. Once you have it paused, you can set the configuration and download K-STAR (NOTE!! With FPM and K-STAR 8+, the Phase II zone list is sent appended to the download, so it only gets set when downloading code!! -- SNM can set the zone list any time -- although the details of how we did that escape me at the moment). AppleTalk routing; If you set VERY LITTLE configuration, K-STAR will autoconfigure, either learning information, or supplying it. If you set some things, but not others, autoconfiguration may be disabled. IP; Most people will probably want to use the box to IP-enable LocalTalk Mac's. The simplest way is to use K-STAR IP, and supply "dynamic" addresses. The Mac IP addresses will directly follow the FastPaths, so assign a big enough block. MacTCP has an option "dynamic", which you DO NOT want to use (it means randomly pick an address to use!!) -- you want to use a "server" assigned address. I can't (off the top of my head) think of any other pitfalls. -phil