root@apal.hanse.de (Andreas Mueller) (04/21/91)
-- I often read about 'grounding Pals in the A1000'. How, why and where (which A1000 rev.) is this done ? What kind of Pals are used in the A1000 (I've a Pal A1000 with the Kickstart mem on the mainboard) +----------------------------------------------------------------------------+ | Andreas Mueller | "Emails are welcome:)" | | Phone: ++49 40 251 23 27 | "Strong typing is for weak minds!" | | Hamburg, FRG UUCP: root@apal.hanse.de | +----------------------------------------------------------------------------+
tomb@hplsla.HP.COM (Tom Bruhns) (04/25/91)
root@apal.hanse.de (Andreas Mueller) writes: >I often read about 'grounding Pals in the A1000'. > >How, why and where (which A1000 rev.) is this done ? > >What kind of Pals are used in the A1000 (I've a Pal A1000 with the Kickstart >mem on the mainboard) The PALs (Programmable Array Logic [chips]) are used for, I believe, some address decoding and perhaps some other simple things. Not to be confused with PAL (a television standard that specifies things like scan frequencies and color encoding; see also SECAM and NTSC, other different standards). The PALs are on the daughter board in an A1000, and the ground between the daughter board and the mother board in the unmodified A1000 has shown itself to be marginal, particularly when peripherals are added to the expansion bus. "Grounding the PALs" refers to adding wires from the PAL ground pins to a good ground point on the mother board. I did this with two pieces of braid from RG-58/U coax cable on my A1000 and saw some improvement, both on a 'scope probing 'ground' and in ability to operate without errors with memory added externally. I understand that it also helps to change the PALs to logically equivalent but faster or lower power or 'cleaner' PALs. I haven't needed to do that...
tomb@hplsla.HP.COM (Tom Bruhns) (05/02/91)
root@apal.hanse.de (Andreas Mueller) writes: >I often read about 'grounding Pals in the A1000'. > >How, why and where (which A1000 rev.) is this done ? etc. Personal to Andreas: (apologies to net) I tried to reply to your email query, but the mail bounced. I would be surprised if European A-1000's don't have a daughterboard and PALs; it's inside the case, and plugs into the main (mother) board. It is towards the front of the computer, at the center. The PALs have nothing to do with the machine being an NTSC or a PAL video format machine. They do some low level logic stuff more efficiently than standard TTL chips. They are typically used for address decoding, and that can be where the "faster/cleaner" helps out. Local dealers that do repairs should have at least heard about the PAL problems, and most around here have or can get the faster/cleaner PALs and optionally install them for you. I have not had to do that upgrade, but have heard that it does indeed solve problems in many cases for people who have tried to expand their A-1000's. If you have the appropriate experience and access to tools, programming your own PALs should be fairly easy; you would 'clone' the existing ones.