mvadh@cbnews.ATT.COM (andrew.d.hay) (02/01/90)
In article <19876@ditka.UUCP> kls@ditka.UUCP (Karl Swartz) writes:
[]
"If your card has sockets for the memory chips and the associated
"control circuits all you have to do is populate the memory array
"and change a couple of jumpers. Otherwise, you're out of luck --
"there are PALs and/or custom ICs in the control section that you
"won't be able to get.
not true!
we've converted several ports-only boards here (using a
ports-and-memory board as a guide), and there's nothing special in the
memory logic at all. it's all standard ttl and discretes and a
resistor pack or two.
--
Andrew Hay +------------------------------------------------------+
Ragged Individualist | But I thought we were *ALL* iconoclasts! |
AT&T-BL Ward Hill MA | I was just trying to fit in!!! |
a.d.hay@att.com +------------------------------------------------------+kls@ditka.UUCP (Karl Swartz) (02/03/90)
In article <13651@cbnews.ATT.COM> mvadh@cbnews.ATT.COM (andrew.d.hay,54242,wi,1d007,508 374 5484) writes: >In article <19876@ditka.UUCP> kls@ditka.UUCP (Karl Swartz) writes: >"If your card has sockets for the memory chips and the associated >"control circuits all you have to do is populate the memory array >"and change a couple of jumpers. Otherwise, you're out of luck -- >"there are PALs and/or custom ICs in the control section that you >"won't be able to get. > >not true! >we've converted several ports-only boards here (using a >ports-and-memory board as a guide) ... it's all standard >ttl and discretes and a resistor pack or two. Right you are! My hardware knowledge goes little beyond that which can be accomplished with a Phillips screwdriver (and sometimes not even that far), so I was just repeating what I'd heard before. But since I just got a ports-only combo board I was curious to see just what the strange chips are. Low and behold, it was all stuff that even I could recognize as being readily available. With a bit of help from my EE housemate I believe I nailed down all of the differences between the two boards: ICs (note that rows are strangely designated: A, B, C, P, H, J, K) 1 74AS74 (1B) 2 74LS280 (2C, 2P) 1 74F00 (2H) 1 74F32 (2J) 1 74F08 (3A) 2 74F138 (3H, 3J) 8 74F258 (3K, 4A, 4B, 4C, 4P, 4H, 4J, 4K) - spare (11J) 54 41256-15 (columns 5 - 10, all nine rows) socket these; array need not be fully populated Resistors 2 33 ohm, 5%, 1/4 watt (R1, R2) - remove (R3, R8) 1 10X-1-102 (RP1) replacement part 1 10-1-560 (RP11) replacement part 10 8X-2-330 (RP2, RP3, RP4, RP5, RP6, RP7, RP8, RP9, RP10, RP12) Capacitors - remove (C18) 29 0.01 mf (C7, C19, C49, C50, C72, C96, C111, C10, C24, C42, C52, C63, C74, C81, C99, C113, C12, C26, C44, C54, C65, C76, C83, C101, C115, C28, C56, C78, C103) same type as C5 29 0.1 mf (C71, C97, C8, C23, C41, C51, C62, C73, C80, C98, C112, C11, C25, C43, C53, C64, C75, C82, C100, C114, C13, C27, C45, C55, C66, C77, C84, C102, C116) same type as C4 Jumpers 3 2-pin Molex jumper blocks (W1, W2, W3) Notes: 1. The boards that I compared (a 1.5 MB combo and a ports-only "combo") are Rev. E so all differences should be isolated to memory versus non-memory, but no guarantees. 2. Resistors R3, and R8, and capacitor C18 should be removed. 3. IC location 11J is not used. 4. Resistor packs RP1 and RP11 have differenet packages, but I couldn't discern any part numbers on the ports-only board, so they may in fact be electrically identical. 5. DRAMs can be 150ns parts, though when I checked today 120ns parts and even 100ns parts were actually cheaper than 150ns pieces. No point in buying slow if they cost you more! 6. See my previous post or the "EIA/RAM COMBO BOARD Installation Guide" for proper settings of jumpers W1 - W3, and for which columns to populate if you want less than the full 1.5 MB. 7. Compare your board to one that already has memory if you can. I haven't upgraded one myself, I just compared my two boards and may have missed something. (Use the information herein at your own risk. Your mileage may vary. Offer void where prohibited. Unleaded fuel only, baby on board, and all that other drivel that makes the lawyers happy. :-) ) -- Karl Swartz |UUCP uunet!apple!zygot!ditka!kls 1-408/223-1308 |INet zygot!ditka!kls@apple.com "I never let my schooling get in |BIX kswartz the way of my education."(Twain) |Snail 1738 Deer Creek Ct., San Jose CA 95148