tinyguy@quiche.cs.mcgill.ca (Yeo-Hoon BAE) (09/10/90)
Hi, I am one curious Amiga user who has a question about type of ram chips that computers use... I understand that there's 16bit and 32bit rams available, and to get the full performance out of Accelerators(020/030 based), you NEED 32 bit memory. So far so good, BUT they cost much more than the average 16bit chips used on 2000. So, ok, I guess it's 32bit, and it has faster access time, so that's reasonable. Then I talked to this guy who used to own Mac SE, and now he owns Mac SE/30(which is 030 based). He also claims that there is no such a thing as 16/32 bit. On Mac, they all use the same type of chips(SIMM), the only difference if that faster machine requires faster memory. So why doesn't Mac require more expensive 32 bit memory and still able to perform reasonably? Is it the way these machines are designed? I heard that 32bit processors are VERY slow with only 16bit memory. Any help would be appreciated. ************************************************************************* * Yeo-Hoon Bae * Amiga /// * * tinyguy@calvin.cs.mcgill.ca * 2000 /// * * tinyguy@quiche.cs.mcgill.ca * \\\/// * * Amiga2000 + 3MB + 48MB HD + KX-P1124 + DiamondScan * \XX/ * *************************************************************************
daveh@cbmvax.commodore.com (Dave Haynie) (09/11/90)
In article <3937@quiche.cs.mcgill.ca> tinyguy@quiche.cs.mcgill.ca (Yeo-Hoon BAE) writes: > I understand that there's 16bit and 32bit rams available, and to get >the full performance out of Accelerators(020/030 based), you NEED 32 bit >memory. There's no such thing as 16 or 32 bit DRAMs. Most DRAM chips are either 1 or 4 bits wide. The memory SYSTEM, on the other hand, is generally an collection of memory chips that's built as wide as the CPU you're hooking up to it. A 68000, with its 16 bit data bus, will hook up nicely to a 16 bit wide memory system, which could be made from 1-bit wide memories in groups of 16 or 4-bit wide memories in groups of four. One of the main advantages of hooking up a 32 bit CPU, such as a 68030, is that you double the width of the data bus. So, all things being equal, the chip could run about twice as fast. However, that can only happen if the bus width of the memory system attached to that 68030 is 32 bits wide. As it happens, most 68030 systems also run at a much higher clock speed, so the memory devices used in 32 bit systems tend to be higher speed, 80-100ns parts rather than the 150ns parts used in most 16 bit Amiga systems. >So far so good, BUT they cost much more than the average 16bit chips used on >2000. So, ok, I guess it's 32bit, and it has faster access time, so that's >reasonable. The ONLY real difference is device speed. In some cases, there are package differences; for example, the A2091 and A2630 both use the same basic part, a 256K x 4 DRAM (also the part on the A2000-B Rev 6 motherboard). However, the A2091 (and 2000) use the DIP (Dual-Inline Package) version of this part, at 120ns or 150ns, while the A2630 uses the ZIP (Zig-zag Inline Package) version at 100ns. >Then I talked to this guy who used to own Mac SE, and now he owns Mac >SE/30(which is 030 based). He also claims that there is no such a thing as >16/32 bit. On Mac, they all use the same type of chips(SIMM), the only >difference if that faster machine requires faster memory. He's basically correct. >So why doesn't Mac require more expensive 32 bit memory and still able to >perform reasonably? Because there's no such thing as a 32 bit memory device. >Is it the way these machines are designed? I heard that 32bit processors are >VERY slow with only 16bit memory. But that's memory SYSTEM, not memory CHIP. Macs don't have add-on memory boards of any kind. Most have a row or two of SIMM (Single Inline Memory Module) devices. You get your Mac with 1 Megabytes, and you can throw out the old SIMM and replace it with one four times larger, so you can expand up to 16Megabytes on some machines. The same thing with the Amiga 3000; you have sockets for up to 16 Megabytes of ZIP memory, and you simply plug in the devices. Now take an A2000, and add an accelerator, the Imtronics '030 card for instance. What you get is a fast 32 bit CPU, but the only memory so far is the memory your Amiga has on the motherboard or in the expansion bus. This is all 16 bits wide, since the A2000 is a 16 bit computer. The '030 won't go much faster, and in some cases it may go even slower, with that 16 wide bit memory system you're hooking it to. So you go out and buy another memory SYSTEM, the Imtronics 32 bit memory card, and all of sudden the CPU starts going much faster, thanks to [a] a 32 bit wide memory system, and [b] a faster memory system. That's the main reason you can't buy a 32 bit card like the A2630 from Commodore without 32 bit memory. And why all fully 32 bit computers like A3000 or Mac II come with 32 bit wide memory systems. >* Yeo-Hoon Bae * Amiga /// * -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy Get that coffee outta my face, put a Margarita in its place!
billsey@agora.uucp (Bill Seymour) (09/11/90)
In article <3937@quiche.cs.mcgill.ca> tinyguy@quiche.cs.mcgill.ca (Yeo-Hoon BAE) writes:
:
: Hi, I am one curious Amiga user who has a question about type of ram
:chips that computers use...
: I understand that there's 16bit and 32bit rams available, and to get
:the full performance out of Accelerators(020/030 based), you NEED 32 bit
:memory. So far so good, BUT they cost much more than the average 16bit
:chips used on 2000. So, ok, I guess it's 32bit, and it has faster access
:time, so that's reasonable. Then I talked to this guy who used to own
:Mac SE, and now he owns Mac SE/30(which is 030 based). He also claims
:that there is no such a thing as 16/32 bit. On Mac, they all use the
:same type of chips(SIMM), the only difference if that faster machine
:requires faster memory. So why doesn't Mac require more expensive 32 bit
:memory and still able to perform reasonably? Is it the way these
:machines are designed? I heard that 32bit processors are VERY slow with
:only 16bit memory.
:Any help would be appreciated.
The ram chips that are used both in 16 bit applications and 32 bit
applications are the same chips. It's just the way the board is designed
that's different. On a 16 bit board, there are 16 data lines going to those
ram chips. On a 32 bit board there are 32 data lines going to the ram chips.
If you design in chips that are one bit wide (256Kx1, 1Mx1, 4Mx1) then you
will need to add chips in 16 chip increments for a 16 bit wide board and in
32 chip increments for a 32 bit wide board. You use correspondingly less
chips if you design in chips that are 4 bits wide (64Kx4, 256Kx4, 1Mx4).
Not that either way, you end up using the same total number of chips on
the memory board. (ie., 32 1M chips for 8M or ram.)
On a typical 32 bit wide board, there are a few more components
than on a 16 bit wide board. That's because you have to buffer each of
those data lines, and there are twice as many data lines on the 32 bit
board. You also tend to build smaller numbers of board when you design
32 bit wide boards, since there is a much smaller user base for systems
that are using your 68020/68030 card. You also tend to use faster chips,
just for performance. On a 16 bit wide board, you're typically designing
for the Zorro II bus, which runs at 7MHz. You can get by with 150ns chips
and run at zero wait state at 7MHz. If you're trying to run at 25MHz,
you won't get zero wait states even with 60ns chips! Note that five wait
states at 25MHz is still faster than no wait states at 7MHz...
Between lower volumes and faster chips, the costs are a lot higher
for 32 bit wide board than for 16 bit wide boards. Even though the memory
itself is the same cost, or with a very small difference, anyway.
:
:
:*************************************************************************
:* Yeo-Hoon Bae * Amiga /// *
:* tinyguy@calvin.cs.mcgill.ca * 2000 /// *
:* tinyguy@quiche.cs.mcgill.ca * \\\/// *
:* Amiga2000 + 3MB + 48MB HD + KX-P1124 + DiamondScan * \XX/ *
:*************************************************************************
--
-Bill Seymour ...tektronix!reed!percival!agora!billsey
=============================================================================
Bejed, Inc. NES, Inc. Northwest Amiga Group At Home Sometimes
(503) 281-8153 (503) 246-9311 (503) 656-7393 BBS (503) 640-0842billsey@agora.uucp (Bill Seymour) (09/11/90)
In article <14331@cbmvax.commodore.com> daveh@cbmvax.commodore.com (Dave Haynie) writes: :In article <3937@quiche.cs.mcgill.ca> tinyguy@quiche.cs.mcgill.ca (Yeo-Hoon BAE) writes: : :> I understand that there's 16bit and 32bit rams available, and to get :>the full performance out of Accelerators(020/030 based), you NEED 32 bit :>memory. : :There's no such thing as 16 or 32 bit DRAMs. Most DRAM chips are either 1 or :4 bits wide. I almost hate to jump in and confuse matters, but I notice that in yesterdays Electronic Buyers News, Micron has finally started advertising their 16 bit wide DRAMs. They have a 64Kx16 DRAM in either a 40 pin ZIP or a 40 pin SOJ. The 256Kx16 versions aren't supposed to be out until the end of the year. :>* Yeo-Hoon Bae * Amiga /// * : :Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" : {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy : Get that coffee outta my face, put a Margarita in its place! -- -Bill Seymour ...tektronix!reed!percival!agora!billsey ============================================================================= Bejed, Inc. NES, Inc. Northwest Amiga Group At Home Sometimes (503) 281-8153 (503) 246-9311 (503) 656-7393 BBS (503) 640-0842